Repair Hints (for several types of video terminals)

 ..............................................................................

This page is a small part of the Video Terminal information archive,
of which the main entry point is

    http://www.cs.utk.edu/~shuford/terminal_index.html

 ...Richard S. Shuford

 //////////////////////////////////////////////////////////////////////////////

General note:

Technical information for various electronic devices, including some terminals,
had been available in the "PhotoFact" document series published by

    Howard W. Sams Company
    2647 Waterfront Parkway East Dr.
    Indianapolis, IN  46214-2012  USA
    voice: +1 317/298-5400

 -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- --

A web site with repair advice for video monitors:
"Service Engineers Forum"
http://www.e-repair.co.uk/index.htm

A web site for a parts and component supplier in Kentucky:
http://www.radioelectronics.com/
Radio-Electronic Equipment Co, Inc.
480 Skain Ave.
PO Box 1209
Lexington, KY 40508
+1 859/255-6661

 -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- ---- -- --

Newsgroups: vmsnet.pdp-11
Path: cs.utk.edu!emory!gatech!howland.reston.ans.net!usc!elroy.jpl.nasa.gov
      !ncar!uchinews!rover.uchicago.edu!frank
Message-ID: <1JUN199310352027@rover.uchicago.edu>
News-Software: VAX/VMS VNEWS 1.41    
Sender: news@uchinews.uchicago.edu (News System)
Reply-To: frank@rover.uchicago.edu
Organization: Joint Center for Radiation Therapy
References: <C7rIJs.7JD@sunfish.usd.edu>
Date: Tue, 1 Jun 1993 16:35:00 GMT
From: frank@rover.uchicago.edu (Frank - Hardware Hacker - Borger)
Subject: Re: Help with LA100 power supply

In article <C7rIJs.7JD@sunfish.usd.edu>, mjohnson@charlie.usd.edu writes...
>
> I was recently given an LA100-PC printer by another PBS station.
> Unfortunately, the power supply in this printer has grown weak and
> no longer has enough oomph to fire all or most of the pins in the
> printhead at once.  This causes characters with vertical lines like
> "1", "I", "l", etc. to be faint or unreadable.
> 
	Long ago, DEC techs (and others,) would troubleshoot boards in
	the field, because boards cost so much. Now the boards are cheap,
	the techs cost a lot more, so board swap is financially better.

	Assuming from your return address that you have some access to
	a reasonably equipped service bench, the first thing I would do
	would be to run a capacitor analyzer on the large filter caps on
	the power supply. I would generally prefer to use a unit that can
	measure the cap's series resistance also, not just capacity.

	Note also that this can happen to caps from just sitting.  It sounds
	like old wives' tales, but it makes sense to rejuvenate a power supply
	that has been sitting for a relative long time, (over a year or more),
	by putting it on a Variac and slowly raising the voltage.

-- 
Frank R. Borger - Physicist     ___      "Have the accordion player sound the
Michael Reese - U of Chicago   |___      charge!" - "He can't sir, he took a
Center for Radiation Therapy   | |_) _   bullet in the bellows during 'Lady of
net: Frank@rover.uchicago.edu    | \|_)  Spain.'" - "Good!"  Dave Barry
ph: 312-791-8075 fa: 791-2517       |_)  

 //////////////////////////////////////////////////////////////////////////////

X-Date: 27 February A.D. 1995
X-From: shuford@cs.utk.edu

Here is a company that sells refurbished DEC, Televideo, and 
Wyse terminals and dot-matrix printers.

Also, the company will repair most brands of terminals for a flat rate
of $79.00 (US).

    Computer Hardware Resources, Inc.
    Houston, Texas
    WATS voice:  1-800/410-6161
    POTS voice: +1 713/683-8977

 /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

    United Service Applications Inc., is a "Depot Level" computer-service
    company; monitors, PCs, and flat-panel displays (including LCDs) repaired.

    http://www.tdmdesign.com/usai/MONITOR.HTM

    United Service Applications, Inc.
    Suite O-8
    17875 Skypark Circle North
    Irvine, California 92714
    Voice: +1 714/757-3266
      Fax: +1 714/757-3263
    Email: <usa4serv@AOL.COM> 


 //////////////////////////////////////////////////////////////////////////////

>Newsgroups: comp.terminals
>Date: Sun, 19 Jul 1998 10:19:53 -0400
>From: Steven <slai2@ix.netcom.com>
>Subject: device to repair terminals
>
>I try to repair computer terminals of the company I work in.
>I know there is a device which I can hook up to the port in
>the back which can recirculate the keyboard signals as input
>signals to the terminals while I repair the communication
>board problem. Anyone knows what this device is called
>and where can I get it?  


What you want is a serial loopback connector.

Try Black Box Corporation or Digikey. 

    http://www.blackbox.com/
    voice: +1 724/746-5500
      fax: +1 724/746-0746

    http://www.digikey.com/
    voice: 1-800/344-4539
          +1 218/681-6674
     fax: +1 218/681-3380

 ...RSS


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: utkcs2!transfer.stratus.com!news.bbnplanet.com!feed2.news.erols.com
      !erols!news.magicnet.net!nntp1.jpl.nasa.gov!netline-fddi.jpl.nasa.gov
      !helios!litwin
Organization: Jet Propulsion Laboratory (NASA)
Message-ID: <6p2acp$jt2@netline.jpl.nasa.gov>
References: <35B20089.DC9B1FB7@ix.netcom.com> <35B37E5E.D1F01DD@rmi.net>
Date: 21 Jul 1998 14:59:37 GMT
From: Todd Litwin <litwin@helios.jpl.nasa.gov>
Subject: Re: device to repair terminals
 
Original question:
>>
>> I try to repair computer terminals of the company I work in.
>> I know there is a device which I can hook up to the port in
>> the back which can recirculate the keyboard signals as input
>> signals to the terminals while I repair the communication
>> board problem. Anyone knows what this device is called
>> and where can I get it?
 
One response:
>
>It's called a "loopback plug". Usually a DB-9 or DB-25 connector with
>pin 2 connected to pin 3.
>What you should use is generically called a "break-out box". Usually has
>LEDS, test points, etc so you can effectivly troubleshoot other
>interface problems, etc.
>Available from any good test equipment or cabling vendor.


Actually, if you only want to loop back the output to the input, then you could
do what I do. Take a paper clip; unfold it and bend it into a U; stick the 2
ends in sockets for pins 2 and 3 (assuming your terminals have female DB-25
connectors). I've done this for years, and it's worked just fine. And it's a
lot cheaper and more convenient than buying fancy equipment. (Fancy equipment
is also nice for many other situations; it's just not needed here.)
 
-- 
                Todd Litwin
                Jet Propulsion Laboratory
                (818) 354-5028
                Todd.E.Litwin@jpl.nasa.gov


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Message-ID: <eZuc6.178875$w35.32632228@news1.rdc1.nj.home.com>
References: <3A72561E.94A2B9E3@home.com>
NNTP-Posting-Host: 24.13.83.35
Date: Sat, 27 Jan 2001 07:42:02 GMT
From: "dls2" <dlshearer@home.com>
Subject: Re: Making a loopback plug

"Calyth" <calyth@home.com> wrote:
> Since I was unable to locate a loopback plug, I'm going to
> make one.  This one is going to put on a Memorex 2192-c
> with a 25pin serial port on the back.  I've got word that I
> could put the 2 and 3 pin together, but is there any other
> pin that I have to solder together?


Solder?  What's wrong with using an ordinary paperclip?

Unless you need to establish flow control, only pins 2 & 3
need to be connected, for a simple loopback connection.

Do you think the fact that only a paperclip is required
might explain why you were unable to find a loopback
plug, despite the relative abundance of passthrough
and null-modem serial cabling?

  --  Derrick Shearer

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: utkcs2!darwin.sura.net!mips!think.com!ames!agate!stanford.edu!rutgers
      !att!cbfsb!cbnewsb.cb.att.com!wa2ise
From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Subject: Re: VT220 questions
Message-ID: <1992May10.222121.20507@cbfsb.cb.att.com>
Date: 10 May 92 22:21:21 GMT
References: <1992May6.170201.12039@phillip.edu.au>
Sender: news@cbfsb.cb.att.com
Organization: AT&T Bell Labs
Lines: 18

In article <1992May6.170201.12039@phillip.edu.au>,
 t9114145@phillip.edu.au writes:
>
>I've just acquired a VT220, made in 1985. 'setup' says V2.00.
> 
>How do I connect a printer to it, i.e. what are the pinouts to make a 
>DEC-to-25 pin serial adaptor. Also does anyone have a standard set of
>pinouts for a 25-pin serial printer's 25-pin D?

 
I'd like to know this, too (can't RTFM 'cause I don't have a manual!)


>The screen is very jittery right after it gets turned on, but smooths
>out once it's warmer until you can't see the jitter any more. Anyone
>have any suggestions what this might mean or how it could be fixed? The
>20-odd VT220's at college don't do this.


My VT220 had jitter.  Found, in my case, it was a dirty horizontal hold
trim pot.  To get to it, you have to take the back off.  It's on the left
side if the flat circuit board, foward (if memory serves right).  I replaced
it in mine (a 5K trimpot, think I got the replacement from Radio Shark).


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: utkcs2!gatech!ncar!virga.rap.ucar.edu!ren
Message-ID: <1992Jun5.142628.1101@ncar.ucar.edu>
Keywords: Sources for replacement terminal parts
Sender: news@ncar.ucar.edu (USENET Maintenance)
Organization: Research Applications Program/NCAR, Boulder, CO
Date: Fri, 5 Jun 1992 14:26:28 GMT
From: ren@virga.rap.ucar.edu (Ren Tescher)
Subject: SUMMARY: VT-320 flyback source needed

I wrote:
>
>Yesterday my VT-320 smoked.  Opening the case I found a cracked and
>melted flyback transformer.  I haven't checked to see if it took the
>Horizontal Output Transistor (H.O.T.) with it.  Nor have I called 
>DEC for a part number/price.  No part # is on the flyback.  I have
>replaced flybacks many times before (let me tell you about my RCA
>television repair days!).  Has anyone replaced the flyback before,
>and where did you get it?  The Dalbani catalog did not have a DEC
>category.

From: Blair Groves <blair.groves@canrem.com>
|
|Ren, you might try calling Sharon Industries in San Jose California,
|they are at (408)-456-1600... they have a lot of parts for TeleVideo
|terminals mainly, and all the other popular terminal brands. They are
|pretty reasonable about prices. Terry Torres can look after you there.


From: ssi!cjr@uunet.UU.NET (Cris J. Rhea)
|
Try Computer Component Source, Inc. (1-800-356-1227)
A VT 320 FB is 17.99 qty 1.
[note: They were the only ones whose catalog I've received so far, and
they also have a Wyse-60 flyback kit for $11.99! ren]

From: George Konstantinopoulos <george@bert.eecs.uic.edu>
|
Try CRC Components Inc.  (800)822-1272  or  (714)468-9711

DEC wants a $160 to replace the motherboard! (They won't sell the part).

Thanks to those who replied!
ren n0pvi
dona nobis pacem

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: misc.forsale.computers,misc.forsale,comp.terminals
Path: utkcs2!darwin.sura.net!haven.umd.edu!uunet!sun-barr!decwrl!pa.dec.com!alf.dec.com!easy.enet.dec.com!mitcham
Message-ID: <1992Nov9.115318.9160@netnews.alf.dec.com>
Keywords: VT220  terminal
Lines: 25
Sender: news@netnews.alf.dec.com (USENET News System)
Reply-To: mitcham@easy.enet.dec.com ()
Organization: Digital Equipment Corporation
References:  <Bx9x7z.A98@aplcenmp.apl.jhu.edu>
Distribution: na
Date: Mon, 9 Nov 1992 11:53:18 GMT
From: Andrew Mitcham <mitcham@easy.enet.dec.com>
Subject: Re: VT220 Terminal


Corrective action as suggested by the VT220 Pocket Service Guide:

VT220 Keyboard Error - 4	1.  Check to see if keyboard is plugged in
				    (re-seat it, even if it is. -AM)
				2.  Replace the keyboard (if you have another
				    terminal, try its keyboard -AM)
				3.  Replace terminal controller board
				4.  Replace power supply / monitor board

Hopefully it is only a matter of the keyboard cable not seating properly.
Otherwise, it looks as though repair may be in order.

Good luck,

-Andy
-- 
  +---------------------------------------------------------------------+
  | Andrew Mitcham			|  The opinions expressed here  |
  | Digital Equipment Corporation	|  are my own and not those of  | 
  | Customer Support Center		|  my employer unless otherwise |
  | Alpharetta, Georgia			|  stated.                      |
  | email:  mitcham@rhett.enet.dec.com	|                               |
  +---------------------------------------------------------------------+

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: cs.utk.edu!news.msfc.nasa.gov!bcm!cs.utexas.edu!news.sprintlink.net
      !beyond.escape.com!escape.com!rjw
Date: Sun, 19 Mar 1995 20:57:11 -0500
Message-ID: <Pine.SUN.3.91.950319205633.23042Z-100000@escape.com>
From: Internet Consulting <rjw@escape.com>
Subject: Monitor repair and sales...

    Micro Technology System
    260 Main St
    Hackensack, NJ 07601

     Ph: +1 201/343 6605
    FaX: +1 201/343 6894

Micro Technology System specializes in all PC parts repairs, including 
Monitor repairs @85, k.brds@30,floppy drives @25,mac f.d@40,at/xt power 
supplies @30, system brd from $50, terminals $125.

MTS can also supply all your system and peripheral needs at competitive 
prices.

For example: 14" SVGA int $165, 14" SVGA n.i 0.28 $185;  give us a call.

MTS has in-house CNE to answer all your technical questions. 
Our technical support is free.

MTS provides on-site or in-house repairs to all makes of computers.       
Lans and cabling jobs done at low rates.

20 mile pick-up & delivery service offered @6 for one piece and $10 for 
two or more pcs. pls call for schedule.

for more info call
mts +1 201/343 6605
fax +1 201/343 6894


Escape.com takes no part in this ad.
Posting done by RJW Internet Consulting <rjw@spring.com>

 //////////////////////////////////////////////////////////////////////////////


[ARCHIVER'S NOTE:  the Stratus V102 video terminal referred to below
 is an OEM version of the Televideo 955.]

 ..............................................................................

Message-ID: <6DF363942AA8D311937A00105AABE7BBDBFDD7@syssvr3.descc.com>
Organization: Double Eagle Steel Coatings
Date: Mon, 1 Mar 2004 09:30:47 -0500 
To: Info-Stratus*list.stratagy.com
From: "Hogan, Phil" <Hogan*descc.com>
Subject: IS:: v102 repairs (terminals)

Was wondering whether anyone repairs V102 terminals or knows who does?
The company that was doing the repairs for us went out of business.

Anybody using any off-the-shelf terminals instead of V102's?  How's the
functionality and durability?  We use the V102's on the plant floor in a
manufacturing environment and they hold up better than you'd expect.  We
have more keyboard problems than CRT problems.

TIA,
Phil Hogan
hogan@descc.com

 ..............................................................................

Message-ID: <OF5D2A108B.3D30BA79-ON85256E4A.005A1443@qvc.com>
Date: Mon, 1 Mar 2004 11:24:14 -0500
To: Info-Stratus*list.stratagy.com
From: JOE_MATTIA*qvc.com
Subject: Re: IS:: v102 repairs (terminals)

We have been using Black River Computer:

    Gary M Reimer
    Technical Administrator

    Black River Computer, Inc.
    7630 Race Rd.
    North Ridgeville, OH 44039

    Voice: 216/327-7999
    Email: gmr@apk.net
      Web: http://www.blackriver.com/

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.unix.admin,comp.terminals
Path: utkcs2!darwin.sura.net!spool.mu.edu!news.nd.edu!mentor.cc.purdue.edu!noose.ecn.purdue.edu!dynamo.ecn.purdue.edu!wb9omc
From: wb9omc@dynamo.ecn.purdue.edu (Duane P Mantick)
Subject: Re: Leaving terminals on
Message-ID: <wb9omc.719168778@dynamo.ecn.purdue.edu>
Keywords: terminals
Sender: news@noose.ecn.purdue.edu (USENET news)
Organization: Purdue University Engineering Computer Network
References: <ldkpm9INN4ho@lovelady.cs.utexas.edu>
        <1992Oct13.224537.4643@datamark.co.nz> <1bjbsqINNcii@swan.doc.ic.ac.uk>
Date: 15 Oct 92 17:06:18 GMT


Fanning the flames.....  :-)

I think it depends on the situation.  If you have your OWN terminal and
you don't share it with other people, AND you don't use it more than 
8 hours out of a 24 hour day, turn it off.

Caveat: don't turn it on and off and on and off and on and off every few
minutes.  You'll more than likely blow the hell out of it.  If you have a 
terminal in an office, for example, leave it on ALL day and turn it off
at night.

In our public terminal rooms, I incourage people to leave the terminals
ON.  The room is open 24 hours and people USE them 24 hours.  The constant
power-cycling is proven to be detrimental.

More Caveat:  terminals with switching power supplies are more sensitive
to power-cycle transients than terminals with a linear, brute-force
power supply, in general.

Paul Zawada mentioned the WYSE terminals - they are an abortion whether
power-cycled or not.  Our WYSE 50's blow up for no reason other than 
incredibly stupid design features--like electrolytic capacitors located
1/16 inch from a HOT heat sink.  Heat dries out cap, cap fails, terminal
goes boom.  Most common in the WYSE50 is C206 on the MPS board.

The best cap we've found as a replacement is the Nichicon HA series. 
These dudes are DESIGNED for the high current and high heat of a horizontal
deflection circuit.  (Wyse should have used them in the first place....)

You can't really make a blanket statement about power-cycling that applies
in ALL cases.  The best way I could phrase it is:

Don't turn it off if you're coming back in less than an hour.  DO turn it
off if you're NOT coming back for MORE than an hour.  If it's a WYSE,
throw it in the trash....  :-)

Duane Mantick
Engineering Computer Network, Purdue University
Supervisor of Terminal Repair

The above comments only represent my opinion.  Period.

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: cs.utk.edu!darwin.sura.net!howland.reston.ans.net!cs.utexas.edu!swrinde
      !ihnp4.ucsd.edu!ames!erg.sri.com!noose.ecn.purdue.edu
      !constellation.ecn.purdue.edu!wb9omc
Message-ID: <wb9omc.766448821@constellation.ecn.purdue.edu>
References: <bill.766428871@netsys.com>
Date: Fri, 15 Apr 1994 22:27:01 GMT
From: wb9omc@constellation.ecn.purdue.edu (Duane P Mantick)
Subject: Re: Wyse 60 repair help wanted

bill@NETSYS.COM (William Petrisko) writes:
>
>Our maintenance contract on our Wyse 60 terminals has finally
>come to an end, so we are being forced to repair any units that
>die in-house (until we can afford replacement units next year.)

	My condolences.

> Has anyone come up with a cheat sheet/quick-tips sheet for
> repairing common Wyse 60 problems?  Here is the breakdown
> of problems... if anyone has any suggestions, I would 
> appreciate the assistance!

	At my site we have mostly Wyse50's.....

>1) K-in-the-corner problem upon powerup.  Occasionally this
>   can be cleared by holding down the "G" key while powering
>   up... but it eventually returns and stays.  The service
>   manual says that is a "non-volatile RAM error."  What does
>   this mean?  Would replacing U2 (nonvolative memory) fix
>   this problem?  Or is the problem deeper than that?

	Depends.  The problem could be the NVR itself or something
that is a latch or addresses the chip.  You might have to replace
two or three chips to find the REAL problem.

>2) Popped and smoked.  Is there a common capacitor that blows
>   up, other part that blows up, or would this be a flyback
>   transformer problem?

	There is a WYSE 60 flyback kit that consists of:

a) a new flyback, PN 420016-01B  (unless changed since)

b) a new diode for position D203.  Remove the General Instruments
	RGP5100 and install the UF4007 in the kit.

c) a new transistor for position Q202.  Remove the BU406 and
	replace with the 2SC2898 in the kit.

the kit part number (last I knew) was 920064-01.  I don't know a
current price on it.

This worked well on what 60's we had.  I think every single one
failed on this flyback bit....and most of the time the flyback will
show a nice big bulge on its sides, or at the very least some
nasty looking bubbling in the plastic. (typically)

That isn't to say that something else couldn't smoke.  If the 60 is
anything like the 50, it too is a self-nuking device.  :-)

The 50 has a capacitor, C206, in the horizontal deflection circuit.
C206 seems to be the crux of many MPS board problems in the 50.
We replace them here with a Nichicon HA series cap, 4.7 uF at
50 volts.  We get these from Jacque Ebert Associates up in New York.
The HA series cap has a VERY high AC ripple current rating,
and that seems to be the culprit (or at the very least, related
to the culprit) - as  in nearly 3 YEARS of using that capacitor,
we have not had a SINGLE wyse50 come back with a C206 related
problem. At least, not one that wasn't already there.....  :-)

And if you think the HA series is too expensive of a capacitor,
I wish you luck finding another bi-polar cap that has that
high of an AC ripple current rating.  Most of what I've located
isn't even close.

Further hints:  I strongly suggest that if the terminal is over
3 years old and you fix the main problem, go through and replace
most, if not all, of the electrolytic capacitors in the video and
power supply circuits.  Pay particular attention to those near
heat sinks or near hot semiconductors.

I don't know if the 60 runs as hot as the 50's do, but whoever designed
the Monitor/Power Supply board for the 50 ought to be SHOT for having
put electrolytic capacitors within 1/8 or 1/16 of an inch of a
skin-burning hot heat sink.  REAL dumb idea.


>3) Video problems.  Usually lines appearing verically through
>   the display, either after warming up or after smacking the
>   terminal on its side.  It would appear this is a heat-related
>   and/or shock-sensitive (bad connection?) type of problem.
>   Again, are the common parts that fail that I could check for?

	Never seen this one.....

Duane Mantick

 ..............................................................................

Jacque Ebert Associates, Inc.
120 Pratt Oval
Glen Cove, NY 11542-1482
+1 516/671-6123

 ..............................................................................

Component sources:

http://www.galco.com/kwpages/JACQ/CAPA-0001.htm
Galco Industrial Electronics
26010 Pinehurst Dr.
Madison Heights, MI 48071   USA
sales:  1-800/575-5562 
office: 1-800/521-1615
office: +1 248/542-9090
office: +1 248/544-7155

http://www.fouraker.com/JACQUESEBERT.html
1-800/635-0420

L&M Wholesale Electronics
1700 W Waco Dr.
Waco, TX 76701  USA
+1 817/754-4644

 ..............................................................................

Web site specializing in information on capacitors:

    http://www.faradnet.com/

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: cs.utk.edu!gatech!howland.reston.ans.net!news.cac.psu.edu!usenet
From: BJJ@ECL.PSU.EDU (Bryan J Jensen)
Subject: Re: VT101 video woes...
Date: 23 Jul 1993 05:00:39 GMT
Organization: Penn State Engineering Computer Lab
Lines: 15
Message-ID: <22nr9n$orj@genesis.ait.psu.edu>
References: <CAAKnF.4qA@rice.edu>
NNTP-Posting-Host: ecl.psu.edu
In-Reply-To: adam@owlnet.rice.edu's message of Sat, 17 Jul 1993 04:33:15 GMT

In <CAAKnF.4qA@rice.edu> adam@owlnet.rice.edu writes:

> I have a lovely old VT101 sitting here that I inherited.  
> ... I get nada on the video.  

The video board is the one to the side of the CRT with all the pots.

On the video board, The 75uF, 6V capacitor C439 and its neighbor,
diode CR408, have a real bad habit of burning up.

The Flyback transformer or Horizontal Output Transistor sometimes
go bad too, of course, as they seem to in any monitor.  I forget
where the transistor is.

I'd mail this to you, but I've never gotten mail to work from VMS NEWS.


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <880111a3.0208281603.20d1133e@posting.google.com>
Message-ID: <Lchb9.11355$gb.10024@news2.central.cox.net>
Organization: Cox Communications
Date: Thu, 29 Aug 2002 04:14:35 GMT
From: mroberds@worldnet.att.net
Subject: Re: Wyse 60 Problem

On 2002-08-28, Drew Taylor <drewt@loritsu.com> wrote:
| 
| I have a Wyse 60 connected to a linux machine. It worked great for
| months with no problems but all of a sudden one day it stopped
| connecting to the host.
| 
| I checked out the serial line back to the machine with another wy60
| terminal and it worked fine. I also matched the setup of the broken
| wy60 with the setup of the working wy60 to make sure all was in order,
| still no soap.
| 
| It turns on fine, video initializes, keyboard initializes and its able
| to enter setup, but it will not communicate to the host (either via
| the aux or the modem port). Since I have eliminated the physical
| serial line and the terminal setup, I'm guessing it's another problem
| with the terminal.

Something on the modem port has died.  This is pretty common, because
the serial lines are usually long and can pick up lots of noise, voltage
spikes, etc, that get fed back into the port.

The RS-232 ports require positive and negative voltages to operate.
It's possible that you have lost the negative output of the power
supply, which means that about half the bits won't make it out onto
the serial line.  It's remotely possible that you've lost the positive
output of the power supply, but since that one usually powers other
stuff in the terminal, more of the terminal usually dies when it
goes out.

Probably the most common things to go out are the "line driver" and
"line reciever" chips.  These translate the 0V/+5V logic in the
terminal to the +12V/-12V logic on the serial line (driver) and
vice versa (reciever).  They usually bear the brunt of spikes coming
in on the serial port.  The standard chips for this for a long time
were the 1488 and 1489 chips, but there are others.  In many
terminals, the line drivers and receivers are in sockets for easier
replacement.

Since you have a working terminal of the same model, you can probably
troubleshoot it by comparing the two.  The simplest thing is to power
up both terminals without connecting them to the host, and use a
voltmeter to compare the voltages on all pins of the serial port
with respect to chassis ground, the metal shell of the serial port
connector.  This will probably verify that the broken terminal's
port is not putting out the right voltages.

To go farther you'll have to open up the terminal.  This isn't too
bad as long as you stay away from the fat wire to the CRT (10 kV -
25 kV), the board at the neck of the CRT (200 V), and the power
cord connections (120 V).  You might luck out and find something
that's visibly blown up next to the modem port, in which case
replacing it will probably fix the problem.  If not, start comparing
voltages with respect to chassis ground on the same pins in the
broken and working terminals.  This should tell you pretty quick if
one of the power supply output voltages has died.  If the terminal
uses the 1488/1489 line driver chips, or other socketed line drivers,
you may be able to swap parts between the two terminals to get the
broken one working.

If you're not too familiar with component-level repair, it might help
to take a look at

    http://www.repairfaq.org/

and ask questions in the newsgroup sci.electronics.repair.

Good luck!

Matt Roberds

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <880111a3.0208281603.20d1133e@posting.google.com>
    <Lchb9.11355$gb.10024@news2.central.cox.net>
Message-ID: <880111a3.0208291521.241e8e6c@posting.google.com>
Date: 29 Aug 2002 16:21:07 -0700
From: Drew Taylor <drewt@loritsu.com>
Subject: Re: Wyse 60 Problem

I compared the RS-232 port voltages on the working and the bad
terminal and found that all of the voltages were the same, except for
pin 2 (the TXD pin if I remember correctly). The working terminal
returned 12v while the busted one read 10.8v. Other than that, they
both returned 13v on the RTS pins, and 11v on the DTR pins.

Also I opened it up to look for the driver/receiver ICs and found 2
ICs marked MC1489AP and 2 marked MC1488P. Both were unsocketed :(

From this information would it be worth the risk to hunt down and
install new line driver and receiver ICs?

I think it would be very likely that a voltage spike from some source
could have knocked it out since the serial line runs through a
populated telco closet.

Thanks for your help.

-Drew

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <880111a3.0208281603.20d1133e@posting.google.com>
    <Lchb9.11355$gb.10024@news2.central.cox.net>
    <880111a3.0208291521.241e8e6c@posting.google.com>
Message-ID: <nzDb9.29764$gb.14492@news2.central.cox.net>
Organization: Cox Communications
Date: Fri, 30 Aug 2002 05:40:35 GMT
From: mroberds@worldnet.att.net
Subject: Re: Wyse 60 Problem

Drew Taylor <drewt@loritsu.com> wrote:
>
>I compared the RS-232 port voltages on the working and the bad
>terminal and found that all of the voltages were the same, except for
>pin 2 (the TXD pin if I remember correctly). The working terminal
>returned 12v while the busted one read 10.8v. Other than that, they
>both returned 13v on the RTS pins, and 11v on the DTR pins.

Well, there is something different about the broken terminal.  If you
want a little more assurance, and if you can measure the voltages while
the port is hooked up, that might provide a little more info.  First,
measure and note the voltages on the end of the cable coming from the
host, while the cable is unplugged.  Then plug the cable into each
terminal and check the voltages again.  What you're looking for is
voltages that go down a lot (like from 12v to less than 3v) when the
cable is plugged in, which indicate a shorted or damaged driver on
that pin.

>Also I opened it up to look for the driver/receiver ICs and found 2
>ICs marked MC1489AP and 2 marked MC1488P. Both were unsocketed :(

You probably have a 1488/1489 pair for each port.  Being unsocketed
is not too big of a problem, but you will have to unsolder the old
ICs.  I would suggest installing sockets so when this happens again
your life will be simpler.  If you can tell which ICs go with which
port (modem/aux) you can just replace the two on the modem port,
but if not you'll need to change all 4.  The chips are less than
$2 each so this isn't a big deal. 

>From this information would it be worth the risk to hunt down and
>install new line driver and receiver ICs?

Well, you do have a spare terminal so you're not dead in the water.
And the broken terminal doesn't work now, so you probably can't make
it worse by carefully working on it.  It is possible that the damage
didn't stop at the line driver and receiver chips, but quite often
it does.

"Hunting down" should be fairly easy.  The 1488 and 1489 are among
the few chips that Radio Shack still stocks, if you are in the US.
In their 2001 catalog both chips sold for $1.29 each.  The sockets
for them are 2 for $1.

>Thanks for your help.

You're welcome!

Matt Roberds


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <880111a3.0208281603.20d1133e@posting.google.com>
    <Lchb9.11355$gb.10024@news2.central.cox.net>
    <880111a3.0208291521.241e8e6c@posting.google.com>
    <nzDb9.29764$gb.14492@news2.central.cox.net>
    <880111a3.0208301119.3ac6448@posting.google.com>
Message-ID: <880111a3.0209070604.200121c9@posting.google.com>
Organization: http://groups.google.com/
Date: 7 Sep 2002 07:04:28 -0700
From: Drew Taylor <drewt@loritsu.com>
Subject: Re: Wyse 60 Problem

rewt@loritsu.com (Drew Taylor) wrote in message
news:<880111a3.0208301119.3ac6448@posting.google.com>...
> That looks like the problem. The voltage on at least the TXD pin drops
> about 5 volts when the serial line is connected to the busted
> terminal. On the TXD pin there is about an 8v difference between the
> busted and the working terminal.
>
> RadioShack has dropped most of its ICs and it looks like all the line
> drivers were included in the drop, the 2001 commercial catalog that I
> have is pretty much worthless now (looks like they have finally
> eradicated Tech America's product line). DigiKey has a large stock of
> line driver ICs so I plan on using them.
>
> Thanks!
>
> -Drew Taylor
> http://WWW.ElectronicsChat.Org/


I replaced all 4 driver and receiver ICs, and that fixed the problem.
I also socketed them, the way it should have been done in the first
place.

Thanks for the help.

-Drew

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.terminals
References: <880111a3.0208281603.20d1133e@posting.google.com>
    <Lchb9.11355$gb.10024@news2.central.cox.net>
    <880111a3.0208291521.241e8e6c@posting.google.com>
    <nzDb9.29764$gb.14492@news2.central.cox.net>
    <880111a3.0208301119.3ac6448@posting.google.com>
    <880111a3.0209070604.200121c9@posting.google.com>
Message-ID: <UJqe9.111681$gb.21600@news2.central.cox.net>
Organization: Cox Communications
Date: Sat, 07 Sep 2002 17:31:32 GMT
From: mroberds@worldnet.att.net
Subject: Re: Wyse 60 Problem

Drew Taylor <drewt@loritsu.com> wrote:
>
> I replaced all 4 driver and receiver ICs, and that fixed the problem.

Cool!  Thanks for posting back with the solution.  Glad I could be of
assistance.

> I also socketed them, the way it should have been done in the first
> place.

Did you buy 4 extra ICs, which are now in their storage tube taped to
the back of the terminal?  :)

Matt Roberds


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.sys.dec
Path: cs.utk.edu!darwin.sura.net!math.ohio-state.edu!howland.reston.ans.net
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Organization: University of Bristol Physics Department
References: <jrl2.745253160@crux1.cit.cornell.edu>
Summary: I need to open a 220 case but can't
Keywords: vt220 dec terminal
Date: Sun, 15 Aug 1993 17:21:00 GMT
From: ard@siva.bris.ac.uk (PDP11 Hacker .....)
Subject: Re: how to open vt220 case

In article <jrl2.745253160@crux1.cit.cornell.edu>, 
jrl2@crux1.cit.cornell.edu (Jeffrey R. Luszcz) writes...
>
>Hello,
>
>   I have a couple of vt220s which are no longer functioning,
> one a couple of them, the only problem is with their power
> switch, others are jsut dead. I would like to take the good power
> switches out of the DEAD ones and put them in the less dead ones.
>
> The problem is that I can't get the VT220s cases open, even though
> I've taken out all the screws I could find, even the two under the 
> white rubber hider things. Do I have to take off the stand? If so 
> how? Thanks,


I've just fixed a load of VT220's here in Bristol. Here's how I got the case
open:

1) Remove all cables (comms, mains, keyboard, etc) from the back.
2) Place the terminal face down
3) Remove the 3 white plastic caps (1 from rear, 2 from base) with a small
   screwdriver
4) Remove the 3 screws exposed in step 3
5) Pull the case off upwards.

The most common fault seems to be no horizontal hold caused by a o/c preset.
Just twiddle the preset marked HH on the PSU/monitor PCB (flat at the bottom),
and return it to its original position. That's fixed about 10 so far. If you
know what you are doing, do this with the power on, and check the the picture
locks, and then turn it off and on again, and see that the picture comes into
lock again. But be careful - there are high voltages in the VT220 case, and I
wouldn't like anyone to get injured.

Other common faults are ROMs with stuck data pins (swap from other dead
terminals), and buffer failure on both the keyboard and serial ports. They're
the 8-pin ICs near the back of the logic board, and are easy to replace if you
don't mind soldering in ICs

Unlike the VT3xx series, I've never had a PSU or line output failure on the
VT220 family.

-tony

 //////////////////////////////////////////////////////////////////////////////

Path: cs.utk.edu!gatech!newsjunkie.ans.net!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail
Newsgroups: comp.terminals
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References: <3l5an8$8fc@paperboy.ids.net>
Reply-To: psichel@aol.com (PSichel)
NNTP-Posting-Host: newsbf02.mail.aol.com
Date: 27 Mar 1995 10:56:51 -0500
From: psichel@aol.com (PSichel)
Subject: Re: VT240 NVR Error

In Message-ID: <3l5an8$8fc@paperboy.ids.net> you wrote

> I have a VT240 with an LK201 keyboard and VR201 monitor.
>
> At startup it displays the following:
>
> VT240 NVR Error - 10

You're right, this is the Non-Volatile RAM.  These chips can go bad
after a while (rated for 10,000 write cycles).  NVR Error means the
terminal detected a checksum error reading from the NVR.  Sometimes
you can fix this by Restoring Factory Defaults and then Saving Settings.
If that doesn't work, you probably need a new NVR chip.

- Peter


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair,comp.sys.dec.micro,comp.terminals
Path: cs.utk.edu!gatech!nntp.msstate.edu!emory!swrinde!howland.reston.ans.net
      !spool.mu.edu!bloom-beacon.mit.edu!ai-lab!bronze.lcs.mit.edu!not-for-mail
Message-ID: <36hrca$o4u@bronze.lcs.mit.edu>
Organization: Guest of MIT AI and LCS labs
X-NNTP-Posting-Host: bronze.ai.mit.edu
Date: 30 Sep 1994 16:10:50 -0400
From: moisan@bronze.lcs.mit.edu (David Moisan)
Subject: FOLLOWUP: (Belated) DEC VT240/VR201 problems
Summary: Terminal *and* CRT were fine!


I posted a month or so ago about a DEC VT240 terminal and a VR201C
amber monitor, both apparently not working.

The VT240 I posted about turned out not to have a problem;  I'd
forgotten that it used the LK201 keyboard for its bell.  Plugged in my
DM KB and monitor, voila!  Normal setup screen!

On the VR201, as suggested by Tony, I checked the HV and the CRT pin 
voltages.  Nada.  The only thing getting lit was the CRT heater.  In a 
million years, I never thought the HV would be screwed, but there it 
was (or there it wasn't!)

I swapped boards with my old DECmate monitor with the dim CRT.  
Works perfectly.  

The VT240 is going to my friend, but it looks like he'll have to find a 
new monitor and KB...:/

Thanks much to Tony and Co. for their suggestions!

Dave
-- 
| David Moisan, N1KGH    /^\_/^\   moisan@bronze.lcs.mit.edu      |
| 86 Essex St. Apt #204 ( o ^ o )  n1kgh@amsat.org                |
| Salem. MA 01970-5225     | |     ce393@cleveland.freenet.edu    |
|                                                                 |

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: cs.utk.edu!gatech!newsjunkie.ans.net!newstf01.news.aol.com
      !newsbf02.news.aol.com!not-for-mail
Date: 27 Mar 1995 10:38:29 -0500
Message-ID: <3l6m5l$gkb@newsbf02.news.aol.com>
References: <wb8fozD617sD.H1@netcom.com>
From: psichel@aol.com (PSichel)
Subject: Re: VT-330 Error 4


In message <wb8fozD617sD.H1@netcom.com> you wrote
>
> When I start up my (hamfest special!) new VT330, it complains
> about keyboard error 4, but it keeps on going.
>
>This is with LK201 keyboards that test out fine on my Rainbow.
>
>Does the 300's expect a non-LK201 keyboard?


No, the LK201 is fine for the VT330.  Keyboard error 4 means the
terminal failed to receive the selftest OK result code from the keyboard.
Maybe a key was down, or there's a poor electrical connection to the
terminal (check for dirty or bent pins on the VT330 keyboard connector).

- Peter

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair,comp.terminals
Path: utkcs2!transfer.stratus.com!cam-news-feed2.bbnplanet.com
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      !137.82.194.1!unixg.ubc.ca!alph02.triumf.ca!shoppa
Message-ID: <6csf78$o61$1@nntp.ucs.ubc.ca>
References: <rexstout-2102981641460001@adialup141.ptld.uswest.net> 
            <5u7rc6.912.ln@tweety.athome.de>
NNTP-Posting-Host: alph02.triumf.ca
Organization: TRIUMF, Canada's National Meson Facility
Date: 23 Feb 1998 18:30:00 GMT
From: shoppa@alph02.triumf.ca (Tim Shoppa)
Subject: Re: VT220 problem

In article <5u7rc6.912.ln@tweety.athome.de>,
Olav Woelfelschneider <wosch@rbg.informatik.th-darmstadt.de> wrote:
>
>John Rollins <rexstout@ptld.uswest.net> wrote in comp.terminals:
>JR>
>JR> 1-  I get a keyboard error 4. What does this mean? I already tried another
>JR> cable(from my telephone handset, I hope the wires aren't reversed like on
>JR> a Mac Plus...) and it still gives me the error.
>
> Be careful, such a cable might overheat. It is said there have been fires
> because of prolonged use of a handset cable...
>
>The keyboard does not have very much components. It's either its cpu, then
>you're hosed, or its driver. In the latter case, you might get a replacement
>part somewhere. Not necessarily from radio shack, though... (:
>
>JR>
>JR>The VT220 I have uses a socketed 8051. Pretty east to find and replace, if
>JR>that's what's wrong. Desoldering isn't that hard. but I hate those little
>JR>Radio Shack bulbs. I need to go get some of those desoldering wicks...
>JR>OK, two more questions. How do I get into the keyboard? I see those two
>JR>nuts on the bottom, but there must be more than that holding it together.
>JR>Keyboards are usually rather interesting to take apart. And what is that
>JR>big connector on the back marked "20mA"? I would guess it's some sort of
>JR>power connector for something, but I can't figure out what.
>JR>
>JR>-JR  http://members.tripod.com/~jrollins/index.html - Computers


Actually, there are two other common causes (which you probably ignored
because they were "obvious"):

1.  The modular jack on either end has failed or has separated from the
PC board mount.

2.  The voltage regulator in the keyboard has failed.

In the stock LK201 keyboard, the voltage regulator is just a 7805.  Some
probing with a voltmeter will quickly tell you if the 7805 is getting power
(if not, check the jacks) or not putting out power (in which case, replace
the 7805.)

LK201's aren't exactly rare keyboards - any DEC reseller has them stacked
up by the hundreds.

Tim.

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.sys.dec
Path: cs.utk.edu!nntp.memphis.edu!nntp.msstate.edu!emory!swrinde!cs.utexas.edu
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Message-ID: <3rvoeo$s14@imp.demon.co.uk>
Sender: news@news.demon.co.uk
References: <sbelfi.226.00151761@electriciti.com>
            <28MAY199510213610@vx.cis.umn.edu> <1995Jun2.163308@cchs.su.edu.au>
            <ENIGMA.95Jun14213632@netcom17.netcom.com>
Date: 18 Jun 1995 00:28:24 +0100
From: mike@mmiller.demon.co.uk (Mike Miller)
Subject: Re: Terminals going up in smoke?

enigma@netcom17.netcom.com (Holly L. McGrath) wrote:
>
>Posting for my boyfriend, who knows a lot more about them than I do:
>he says that the flyback transformers start leaking high voltage well
>before they actually start failing, and you can spot this if you take
>the terminal into a dark room and look down into the vents.  The tube
>will glow, but if you see arcing on the high voltage transformer, get
>Corona Dope or if you can't get that get high voltage GLPT and
>liberally coat the transformer.  All of the used VT320's (except one)
>that he has purchased have required this treatment, and are still
>working. 

Sorry, but that's not what's wrong with them; it's the connection from
the CRT to the motherboard. It's a known problem ...crap connectors.

DEC won't recall them, and they burn out.....the brightness is also a
known problem .....open the terminal up and adjust the brighness pot.
I know because  I used to work for DEC as a real engineer not just a
contractor or a x-sme :)


 
 Mike Miller.              " The Quicker This World Stop's Spinning
                                  The Quicker I Can Get Off "

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.sys.dec
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      !lyra.csx.cam.ac.uk!ard12
From: ard12@eng.cam.ac.uk (A.R. Duell)
Subject: Re: Terminals going up in smoke?
Date: 19 Jun 1995 12:33:37 GMT
Organization: University of Cambridge, England
Lines: 30
Message-ID: <3s3qr1$ans@lyra.csx.cam.ac.uk>
References: <sbelfi.226.00151761@electriciti.com>
  <28MAY199510213610@vx.cis.umn.edu>  <1995Jun2.163308@cchs.su.edu.au>
  <ENIGMA.95Jun14213632@netcom17.netcom.com> <3rvoeo$s14@imp.demon.co.uk>
NNTP-Posting-Host: club.eng.cam.ac.uk

mike@mmiller.demon.co.uk (Mike Miller) writes:

>enigma@netcom17.netcom.com (Holly L. McGrath) wrote:

>>liberally coat the transformer.  All of the used VT320's (except one)
>>that he has purchased have required this treatment, and are still
>>working. 

> Sorry, but that's not what's wrong with them...

Well, I've certainly had flybacks (line output transformers) fail in 
VT320's and VT330's. They've actually cracked open, and emitted magic 
smoke. And, they test as shorted on my transformer tester. Getting new 
ones has proved to be rather difficult, though :-(.

I don't recall any connector between the CRT and the logic board, other 
than the tube base and EHT flower, of course. The tube base (which looks 
to be of reasonable quality) is soldered to a small PCB, and I thought 
the wires linking this to the logic board were soldered at both ends. 
Maybe I've just misremembered it, though.

> 
> Mike Miller.              " The Quicker This World Stop's Spinning
>                                  The Quicker I Can Get Off "

-tony

 //////////////////////////////////////////////////////////////////////////////

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: alt.folklore.computers
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      !siva.bris.ac.uk!ard
From: ard@siva.bris.ac.uk (PDP11 Hacker .....)
Subject: Re: VT10x
Message-ID: <5OCT199418413844@siva.bris.ac.uk>
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References: <1994Oct4.044842.28424@picarefy.picarefy.com>
   <hshubs.781284781@BIX.com>
Date: Wed, 5 Oct 1994 17:41:00 GMT
Lines: 53

In article <hshubs.781284781@BIX.com>, hshubs@BIX.com (Howard Shubs) writes...
>jwbirdsa@picarefy.picarefy.com (James W. Birdsall) writes:
> 
>>   What's the difference between the VT100, VT101, VT102, and VT103? I just
>>got several of the last two. The most obvious difference between the 102
>>and the 103 is that the 103 lacks a printer port and has a video in
>>connector, but I'm interested to know whether there are any other, less
>>visible differences.

>I'm not sure what the VT103 was.

I _think_ the VT103 was a VT100 with 4-slot Q-bus backplane in it. The standard
CPU was the LSI11/2 (PDP11/03 CPU), but I am told an 11/73, or even a microvax2
CPU can be got in there.
It's a rather nice object.

> 
> 
>>   Also, one of the 102's is frustratingly close to working. It passes all
>>self-tests, local echo works fine -- it does everything except actually
>>send data (don't know whether it receives or not). I have a little inline
>>RS232 breakout box connected, and any time I hit a key, there seems to be
>>exactly one level transition on the transmit line, then it gets stuck there.
>>I've been through setup a bunch of times; baud, data and stop bits, parity,
>>and everything else are fine as far as I can tell (some of the setup options
>>are pretty obscure). If anybody recognizes this failure mode, I'd like to
>>hear about it.

Maybe a defective clock to the UART chip - but I'll have to check the printset
(schematics) to be sure. They're pretty simple anyway.

> 
>Standard procedure to fix these terminals was to take two broken ones and
>make one working one by swapping boards until one terminal worked and one
>terminal had multiple woes.  I hope you didn't pay a lot for these things

Maybe, if you are from "failed circus" :-). The real way to fix these involves
checking the PSU (linear in the VT101, a nice, easy to repair, switcher in the
VT100).

Then, either fixing the video board (problems on this are simple - the main
failures are the flyback transformer, shorted rectifiers which then kill the
flyback transformer, or blown video output transistors), or fixing the logic
board. Logic board faults are rare, so I've not had any of those to fix
Oh, and please don't swap out video boards. The flyback transformer is _not_
part of the board, so that if a rectifier on the video board is dying, it will
kill the good flyback you've connected it to. I've had to clear up a mess that
started that way.

-tony

Bristol University takes no responsibility for the views expressed in this
posting. They are the personal views of the user concerned.

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
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      !mozo.cc.purdue.edu!constellation.ecn.purdue.edu!wb9omc
From: wb9omc@constellation.ecn.purdue.edu (Duane P Mantick)
Subject: Re: Wyse break
Date: 14 Jul 1995 18:27:31 GMT
Organization: Purdue University
Lines: 136
Message-ID: <3u6cuj$k2m@mozo.cc.purdue.edu>
References: <3tv6p0$3js@news.nde.state.ne.us>
    <sir-1207950626430001@stu.firstsol.com>

sir@firstsol.com (Stu Rutkin) writes:
>
> In article <3tv6p0$3js@news.nde.state.ne.us>,
> chammack@genie.esu10.k12.ne.us (Chris Hammack) wrote:
> >
> > Argh!  I don't turn on the wyse for 3 weeks, and now...no picture!  When 
>
> or back of the cover (Wyse 60's and newer Wyse 50's).  Sounds like the
> monitor/power supply  (MPS) board has croaked.  There are plenty of repair
> services around

	Alternatively, if the user is electronically experienced or
knows someone who *is* (and for God's sake, if you don't know what
you're doing, stay the hell out), you can open up the terminal and check
C206 on the MPS board.  C206 is on the right side of the board (when
viewed from the back) and just forward from the flyback.  This applies
to wyse *50's*. On the 60's, there is a flyback replacement kit that
includes the flyback and a transistor and diode, all of which beefs up
the circuit considerably.

	Back to the wyse50.

	C206 needs to be a bi-polar electrolytic cap, 4.7 uF at 50 volts.
HINT: do NOT use the cheapest one you can find!  Cheap ones don't have
a very good AC ripple current rating.  I suggest the Nichicon HA series;
we have had quite good luck with them here.  Said ripple current rating
on the HA's is given in AMPS, not milliamps like the cheap ones.

	In the wyse50, if it is the FIRST time that the terminal has
failed since new, more than likely be C206 if the symptom is ONLY a
loss of video and everything else seems to work.

	Each time C206 fails, the chance of other things failing goes
UP.  Several service vendors, and possibly wyse themselves, suggested
replacing the 5-pin regulator at U101 (type L200C) when C206 croaks,
although we have not found this to matter much.

	NOTE: if you think you smell ozone, take the back of the upper
case OFF, and power up the terminal.  Turn OFF the lights in the
room and look at the flyback.  If you see ANY pulpleish colored arcing
on the top or sides of the flyback, REPLACE it.  That arcing is
nearly always the source of your ozone smell.  The arcing will usually
appear as very deep purple lines.....

	Further suggestion:  BEFORE you attempt ANY kind of repairs, turn the
power OFF and DISCONNECT the power cord from the terminal.  THEN, and ONLY
THEN, take a BIG screwdriver and discharge the CRT anode to the frame
to get rid of most of the dangerous voltage.  In the wyse, that anode runs
at 14 Kv, and the CRT can hold a considerable residual charge even
AFTER the unit is powered off, and can shock the snot out 
of you.  Therefore, when you discharge, make sure that you don't
come in contact with ANY of the metal parts in question.

	When you pull the MPS board out, take a REAL good look at ALL
the electrolytic capacitors on that board.  If ANY of them appear
bulged or misshapen in ANY way, or badly discolored, REPLACE them.
I suggest using replacements that have a 105 deg. C temperature
rating instead of the usual 85 deg. C rating.

	The top (monitor/power supply) section of a wyse50 runs REAL hot.
If you don't believe that, look at one that is 7 years old or so,
and look for two nice brown spots on the top of the case that are 
directly above internal heat zones.  The plastic of the case actually
discolors from the heat!

	Electrolytic caps don't tolerate being soaked in heat all 
that well, and doing so shortens their life.  Going to a higher rated
cap. (temperature wise) will help this somewhat....

	You have some moron of a designer at wyse or associated
company to thank for many of these problems.  No designer with an
ounce of brains physically locates an electrolytic capacitor
1/16 of an inch away from a HOT heat sink UNLESS he WANTS the
unit to fail as a deliberate design feature.  I am experimenting with
a real neat insulating material to protect the capacitors from
the heat....just a little square of it to block the direct heat radiation
from the caps, NOT enough to prevent the heat sink from 
dissipating the heat in the attached semiconductor.

	BUT, from our experience here there comes a time when the
MPS board is just plain SHOT.  You can still get NEW ones, which
run about $110 or $120.  Quite frankly, that isn't a lot less than
a new terminal....and there are a shitpot of good used terminals
out there for LESS.  You can get SOME MPS boards repaired, but
you don't usually get much of a warranty on them (at least not
from what I've seen).

	My advice on a good used dumb terminal?  Find a good used
ADDS Regent 20 or Lear-Siegler ADM-5 in good condition.

	Things to look for: The Regent 20 should have a Keytronic
keyboard, preferably a late revision; try to get a re20 with a serial
number under 206000 - usually those lower will have the Panasonic K224
monitor in them, generally pretty reliable, ESPECIALLY the K224E4B
later variant.  Those after 206000 usually have an ADDS-built monitor
that sucks.  On the ADM-5's, check out the monitor - if it has the
Zenith-built one with the off-board flyback, avoid it like the plague.

	If it has the Samsung monitor you will do much better.  One
common failure in the Samsung ADM-5 monitor:  C413 on the video board.
Just like the one on the Wyse board, this is a Horizontal Deflection
cap and needs to be a bi-polar electroltyic.  We are also using the
Nichicon HA here with good success.  The original was a 16 uF cap, but
the HA series ends at 10 uF.  This works just fine, BTW, and is also a
50 volt cap.  Typical symptom of a C413 failure will be either no
video, or a dashed vertical line up the center of the screen.

	Only a couple things to watch out for in the re20's
Panasonic monitors:  crappy solder joints on the flyback.  Symptom
is the screen flashes when you bump the terminal.  Just resolder the
flyback and you're in business.  On the early K224 monitors,
C431 and 432 will fail sometimes....you can replace them with about
any equivalent standard electrolytic and they will be good for years.   
On the newer K224E4B, it is someting like C463 and 465.  Same story.
Symptom is a partial raster on the screen and/or a bright dot in the
middle of the screen when you turn the terminal off.  In each unit, one
of those caps just sits and holds a charge until you turn the terminal
off....then it discharges into one of the screen grids to shut off the
electron beam to prevent that bright white spot, which will eventually
etch a nasty dark splotch into the screen.

	Both the Regent 20 and the ADM-5 are jurassic technology, BUT -
they are probably two of the most robust and well-constructed general-
purpose dumb terminals ever built.  Neither of them has very many
"proprietary" parts in them, and while Panasonic has discontinued parts
support for the Regent monitor, the ADM-5 monitor's Samsung flybacks
can still be gotten from a few sources.  They aren't 100% identical,
but do work.

Duane Mantick
Supervisor of Terminal Repair
Engineering Computer Network, Purdue University

Disclaimer: comments made above do not represent any official viewpoint
or endorsement from Purdue University.  Neither them or I are responsible
for what happens if an untrained idiot sticks his fingers where they
don't belong......

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair
Path: cs.utk.edu!gatech!stallion.jsums.edu!news.uoregon.edu!vixen.cso.uiuc.edu
      !howland.reston.ans.net!agate!library.ucla.edu!info.ucla.edu!csulb.edu
      !csus.edu!netcom.com!NewsWatcher!user
From: voicebox@netcom.com (Dave C.)
Subject: Re: Need some tips on repairing Wyse monitors
Message-ID: <voicebox-2207951052250001@192.0.2.1>
Sender: voicebox@netcom14.netcom.com
References: <a03047.805733918@giant> <3u642l$pud@sauron.multiverse.com>
Date: Sat, 22 Jul 1995 17:50:35 GMT
Lines: 26

a03047@giant.rsoft.bc.ca (Russell Owsianski) wrote:

> Also, many of our Wyse 50s make a terrible 'screaming' noise.  I'm guessing 
> thatthis might be the flyback transformer failing.  Is =
> this a common problem for this model?

I have heard of crafty technicians putting a drop of oil on the flyback
transformer core to shut it up. This works only if the transformer is one
of the laminated iron-core types. Ferrite-core types, obviously, won't
benefit from this trick.

In general, Wyse terminals, whose sole raison detre is "CHEEP", have all
had a short life span. Regarding the dim screens: if adjusting the
internal brightness control will brighten the screen, then good for you :)
. If not, then it is probably that the electron gun in the CRT is used up.
TV repair technicians used to use another trick I just remembered: they'd
connect a variable voltage (a bench power supply) to the heater element
pins at the back of the CRT and crank it up (experience and wisdom
determined how much) for a while (ditto, for how long). This would burn
off the deposits on the heater element, which would result in increased
brightness for a (VERY variable) period of time.

Good luck.

Enjoy,
Dave

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: sci.electronics.repair,sci.electronics
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From: "Samuel M. Goldwasser" <sam@stdavids.picker.com>
Subject: Re: Viewsonic 4 horz output transistor?
Date: 17 Jul 1995 01:26:02 GMT
Organization: Picker International
Lines: 26
Message-ID: <3uce7a$pu4@sauron.multiverse.com>
References: <3ucb7d$kd8@osa.osa.com.au>
To: cjh@osa.com.au

cjh@osa.com.au (Clifford Heath) wrote:
>I have been asked to repair a "Viewsonic 4" VGA monitor which has seriously
>popped its horizontal output transistor.  I believe it was a PNP type,
>in a resin package about 3/4" by 1/2" by 3/16" (I don't know the name of
>this package type - do you?).  Unfortunately the label is burnt - can
>anyone help me with identifying the type - I think it says "D" followed
>by four digits?  Otherwise can anyone let me know what Hfe and Vce specs
>are required for this transistor?

FYI, most horizontal output transistors are NPN bipolar.  The 'D'
would mean 2SDXXXX.  2SD is always NPN.  The package is called TOP-3
or some variation on this.  Unfortunately, that is as far as I can
go.  For testing, you can try a variety of replacements including 
probably (I will not pay if these blow up) 2SD1428, 2SD1652, 2SD1556,
2SD1403. The first three have internal damper diodes, the last does
not.  If you have an external damper diode, then it should nto mattter.

There are many others - I just picked these out of the MCM
catalog.  I am not saying to use any of these necessarily as a permenant
replacement, but for testing to determine what if anything else is
fried, they should be fine.  You can even use a TO3 cased transistor
with similar ratings if you have one for testing.

--- sam

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair
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Lines: 25
Message-ID: <3uiu6e$p5h@sauron.multiverse.com>
References: <18JUL199515451924@cats.ucis.vill.edu>
NNTP-Posting-Host: 144.54.161.7
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 1.2b1 (Windows; U; 32bit)
Organization: Picker International
Date: 19 Jul 1995 12:35:26 GMT
To: 135784960@cats.ucis.vill.edu
From: "Samuel M. Goldwasser" <sam@stdavids.picker.com>
Subject: Re: Monitor Vert. Size

135784960@cats.ucis.vill.edu (fuzzy bunny) wrote:
>
>I have been having some difficulties with my monitor. (It acts up with other 
>computer's as well, so it is not the video card.)  The monitor is a 15=inch
>SVGA job that works fine for about half an hour.  At this point,  the vertical
>hold seems to get worse and worse. First the screen starts shaking up and 
>down,
>then the size of the screen shrinks to the middle third of the monitor.  The 
>really weird thing is that when I reset the system,  the startup screen(the 
>one with the energy saver star and memory test) is the right size and does not
>shake.  As soon as the screen changes, however,  it is right back to the 
>smaller size.  I did not see any physical damage to the board inside the
>monitor
>Has anyone else had a problem like this?  How did you solve it?  Any ideas of
>what to check on inside?(I'm an EE, not afraid to pull parts and solder in new
>ones.)  Any help would be greatly appreciated.

Assuming you are not running at an excessive vertical scan rate as
someone else suggests, you probably have a bad cap or other component.
Get a can of 'cold spray' or 'circuit chiller' and use it to cool each
of the parts in the vertical section and power supply.  Just a little
squirt - wait a few seconds to see if there is any effect.

Be careful in there - line voltage and high voltage.

--- sam

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair
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From: "Samuel M. Goldwasser" <sam@stdavids.picker.com>
Subject: Re: Jittery Monitors
Date: 27 Jul 1995 12:15:57 GMT
Organization: Picker International
Lines: 20
Message-ID: <3v801t$b0u@sauron.multiverse.com>
References: <3v7u39$2r0@cantua.canterbury.ac.nz>
To: knoxcj@elec.canterbury.ac.nz

knoxcj@elec.canterbury.ac.nz (c.j. knox) wrote:
>
>G'day. I have several old computers, some of which have unstable
>monitors (VDUs) - they change the size of the text at random. 
>Have had a look at the capacitors, and none are obviously damaged/aged. 
>Would some kind soul suggest a solution? Neither myself nor my test
>equipment are built for high voltages.

Check for bad/cold solder connections, clean and reseat internal
connectors, etc.  Jittery unstable displays are more likely due to
intermittent connections than bad components.  Could also be excessive
dirt/dust/crud buildup causing intermittent corona/arcing but this
is less likely if there are no other symptoms.

Most likely places for bad connections are around the pins of large
components like power transistors, power resistors, transformers,
and connectors.

--- sam

 //////////////////////////////////////////////////////////////////////////////

Sprague Magnetics, Inc.

Parts supplier and depot repair of computer peripherals, professional
audio and professional film/video equipment.  Web site at

    http://www.earthlink.net/~sprague-magnetics/

Conventional contact information:

    Sprague Magnetics, Inc.
    15720 Stagg Street
    Van Nuys, CA  91406
    +1 818/994-6602

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: cs.utk.edu!news.msfc.nasa.gov!elroy.jpl.nasa.gov!swrinde
      !howland.reston.ans.net!math.ohio-state.edu!newsfeed.acns.nwu.edu
      !uicvm.uic.edu!u54294
Organization: University of Illinois at Chicago, ADN Computer Center
Date: Wed, 9 Aug 1995 13:44:45 CDT
From: <U54294@uicvm.uic.edu>
Message-ID: <95221.134445U54294@uicvm.uic.edu>
Subject: Why terms lose setup info?
Lines: 13

I have a collection of Wyse 60's, 160's and ADDS 4000/260's. Periodically
some of them lose some parts of their setup information. I thought that
it might be cosmic rays, spurious transmissions from aliens, or some other
semi-random event, until it started happening to MY terminal. Since
I am the system admin, the problem must now be addressed ;) Sooo...
Does this happen at your site? Is it concentrated in a specific building
or is it goegraphically random (like it is here)? Are specific terminal
models or brands more subject to this than others? What's a mother to do?

Thanks for your time....Nick G.

+------------------------------+----------------------------------------+
| Just another roller-bearing  | Nick Geovanis     U54294@uicvm.uic.edu |
| ...in the Data Warehouse     |     Unix software and sysadmin         |
+------------------------------+----------------------------------------+

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
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      !spectre.sc.intel.com!news	
From: Bennet Wong <bennet_wong@ccm.sc.intel.com>
Subject: Re: Why terms lose setup info?
Date: 9 Aug 1995 21:19:51 GMT
Organization: Intel Corporation
Lines: 35
Message-ID: <40b8pn$qk0@itnews.sc.intel.com>
References: <95221.134445U54294@uicvm.uic.edu>

Some areas you should look into:

1. How old is the terminal? Most terminal used a battery backup RAM to 
   store setup. The avg. life is around 3 yrs.
2. Does user go in anc change the setup w/o letting you know? Did you 
   remember to change and SAVE the setup?
3. Some setup value can be change by an escape sequence (cursor on/off 
   .. etc.) Do you have any progarm that will issue command like this? For 
   example, if your editor sends a change-cursor command during its init cycle 
   and then you go into setup and change other setting, save and exit. Your 
   cursor setting will be change and save also. 
4. May be it is a bug in the Firmware, check with your dealer.
5. Sometime dirty power will cause the setup RAM to fail. If the problem 
   happen in the same location over and over again you may want to swicth 
   location and try again.
6. Very powerful electric dischage close to the terminal will also cause 
   problem.

I hope the info is helpful.

If you want to know why I know so much. I used to work as the Mgr for 
Technical Support and SQA at Wyse. I am also a Sr. F/W engineer before I 
switch to a management role. 

Have fun.

-- 
  Bennet Wong
  Intel Corporation	        
  Internet:    bennet_wong@ccm.sc.intel.com
  Disclaimer:  Unofficial, personal *opinion*.


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
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      !news.tek.com!sptekwv2!boots
From: boots@sptekwv2.wv.tek.com (Darrell Irvin;685-2277;60-850;;sptekwv2)
Subject: Re: Why terms lose setup info?
Date: 15 Aug 1995 19:44:59 GMT
Organization: Tektronix, Inc.,  Beaverton, OR
Lines: 47
Sender: boots@sptekwv2 (Darrell Irvin;685-2277;60-850;;sptekwv2)
Message-ID: <40qtfr$jtg@goodnews.wv.tek.com>
References: <95221.134445U54294@uicvm.uic.edu> <40jrd2$qfm@nexus.polaris.net>
Reply-To: boots@orca.wv.tek.com
NNTP-Posting-Host: sptekwv2.wv.tek.com

In article <40jrd2$qfm@nexus.polaris.net>, waters@polaris.net (Jonathan Waters)
 writes:
|> In article <95221.134445U54294@uicvm.uic.edu>, <U54294@uicvm.uic.edu> says:
|> >
|> >I have a collection of Wyse 60's, 160's and ADDS 4000/260's. Periodically
|> >some of them lose some parts of their setup information. I thought that
|> >it might be cosmic rays, spurious transmissions from aliens, or some other
|> >semi-random event, until it started happening to MY terminal. Since
|> >I am the system admin, the problem must now be addressed ;) Sooo...
|> >Does this happen at your site? Is it concentrated in a specific building
|> >or is it goegraphically random (like it is here)? Are specific terminal
|> >models or brands more subject to this than others? What's a mother to do?
|> >Thanks for your time....Nick G.
|> >+------------------------------+----------------------------------------+
|> >| Just another roller-bearing  | Nick Geovanis     U54294@uicvm.uic.edu |
|> >| ...in the Data Warehouse     |     Unix software and sysadmin         |
|> >+------------------------------+----------------------------------------+
|> 
|> The problem usually lies in the type of Non Volatile memory (NVRAM) used
|> to store the options.
|> This type of terminal usually has a CMOS memory, with a battery backup.
|> If the reset circuit "jerks" the control lines leading to the CMOS, it can
|> cause what the CMOS thinks is a write pulse. Since the data and address lines
|> are undefined at that point, weird things occur.
|> 
|> The other reason may be pure and simple bugs in the software (firmware)
|> that control these devices.
|> 
|> I was head of R&D for a terminal manufacturer for some years, and know
|> every way of lousing up setup options!
|> 
|> Jonthan

As a design engineer who did terminals for may years I can think of another
potential problem (assuming good design in the first place).  We always took
great care to prevent spurious write pulses on power up.  The battery
can go bad from age, heat, etc.  If your terminals are several years old
this may be the problem.  If it is a silver oxide or lithium cell in a holder
simply replace it.  It it is soldered it is a little more difficult.  NiCad
batteries are bad about dying of old age.  

-- 
	   =========================================================
	   =   Darrell Boots Irvin  boots@orca.WV.TEK.COM	   =
	   =   Network Displays Engineering			   =
	   =   Tektronix Inc.					   =
	   =========================================================

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: cs.utk.edu!gatech!news.mathworks.com!transfer.stratus.com!xylogics.com
      !xylogics.com!not-for-mail
Lines: 33
Message-ID: <40sln8$hle@newhub.xylogics.com>
References: <95221.134445U54294@uicvm.uic.edu>
       <40jrd2$qfm@nexus.polaris.net> <40qtfr$jtg@goodnews.wv.tek.com>
Reply-To: carlson@xylogics.com
Date: 16 Aug 1995 07:44:40 -0400
Organization: Xylogics Incorporated
From: carlson@xylogics.com (James Carlson)
Subject: Re: Why terms lose setup info?

In article <40qtfr$jtg@goodnews.wv.tek.com>, boots@sptekwv2.wv.tek.com (Darrell Irvin;685-2277;60-850;;sptekwv2) writes:
|> In article <40jrd2$qfm@nexus.polaris.net>, waters@polaris.net (Jonathan Waters) writes:
|> |> In article <95221.134445U54294@uicvm.uic.edu>, <U54294@uicvm.uic.edu> says:
|> |> >
|> |> >I have a collection of Wyse 60's, 160's and ADDS 4000/260's. Periodically
|> |> >some of them lose some parts of their setup information. I thought that
[...]
|> |> I was head of R&D for a terminal manufacturer for some years, and know
|> |> every way of lousing up setup options!
[...]
|> 
|> As a design engineer who did terminals for may years I can think of another
|> potential problem (assuming good design in the first place).  We always took
[...]

As yet another engineer who designed terminals in a previous job, we
*never* used CMOS RAMs.  The batteries were too expensive and
unreliable.  We used serial EEROMs instead for parameter storage.  These
things can go bad, though, if subjected to extreme heat or many
thousands of "write" operations.

I'd personally be very surprised to find battery-backed RAM in those
terminals.  I'd start looking for an 8-pin dip in an corner of the
board, with no connections to anything interesting (like video or
keyboard) and no comprehensible markings.  If shorting a couple of pins
on this device during power-up causes the terminal to lose the config
information, then that's probably it ...

-- 
James Carlson <carlson@xylogics.com>            Tel:  +1 617 272 8140
Annex Software Support / Xylogics, Inc.               +1 800 225 3317
53 Third Avenue / Burlington MA  01803-4491     Fax:  +1 617 272 2618

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.os.vms
Organization: Info-Vax<==>Comp.Os.Vms Gateway
Message-ID: <01JB7X43LFHE000OZ3@IST.CERIST.DZ>
Date: Sat, 15 May 1999 08:22:21 +0000 (GMT)
From: L. Benchabane <benchabane@IST.CERIST.DZ>
Subject: Re: NVR error/failure with VT220?

At 20:28 13/05/99 -0600, "Mark" wrote:
>
>Anyone here who might recall a failure of the non-volatile memory of
>a VT220, i.e. loss of the saved Set-Up configuration for
>modem-connected terminal?
>
>The message came up today, but a reentry of whatever settings it
>takes to make this beauty work as my modem connection to the campus
>VAX made everything OK again.
>
>Is this perhaps a sign of a VT220 about to fail completely?
>
>
>  Mark (Please note, I did _not_ pose this to "old"-timers  :-)

The NV RAm is located on E17 in logic board.
It's a 2212 RAM 256x4 . DEC part number is 2120263-01.
NVR failure dont mean that your VT220 is close to die .......

L.BENCHABANE

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair
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From: jstermer@in.net (Jay Stermer)
Subject: Re: Problem with IBM 8515 monitor
Date: Sat, 09 Sep 1995 23:38:08 GMT
Organization: John Jay Stermer, B.S.E.E.
Lines: 16
Message-ID: <42t50p$adb@su3.in.net>
References: <1995Sep4.144101@tudedv.et.tudelft.nl>
            <1995Sep6.214212@tudedv.et.tudelft.nl>
Reply-To: jstermer@in.net

reggermont@et.tudelft.nl (Robbert Eggermont) wrote:

>> I have an IBM 8515 monitor which has a vertical deflector problem.
>I suspect the TDA2030 (I think anyway this is the chip that takes care 
>of the vertical deflection). Is there a way to tell if this chip is 
>defective, without having to turn the monitor on?

>Any hints?  

Most vertical output IC's are fed from the flyback transformer. Inspect
that area for burned resistors. Many times the diode which rectifies the
voltage will short which then opens the fusible resistor that feeds it. If
you find this, you should always replace the IC while you're at it since
it's probably damaged from the burst of unfiltered AC when the diode
failed.

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair
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From: bachman@anatek.mv.com
Subject: Re: Gateway CrystalScan starts to wiggle
Message-ID: <DFKr73.5zp@mv.mv.com>
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Organization: AnaTek Corp., Monitor Repair Data, http://www.anatekcorp.com/
Date: Wed, 27 Sep 1995 17:28:14 GMT
Followup-To: choiw1@intac.com
Lines: 10

Check R331, 91Kohm, 1 watt.  If it is >95Kohms oscillation can occur.  This 
monitor is covered in our monitor repair database at 
http://www.anatekcorp.com/repair.htm
_____________________________
John Bachman
AnaTek Corporation
Monitor Repair Data
http://www.anatekcorp.com/repair.htm

 //////////////////////////////////////////////////////////////////////////////

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From: sam@colossus (Sam Goldwasser)
Subject: Re: Sony KP-5020 Projection TV Picture Shrunk
In-Reply-To: craigr@magicnet.net's message of 24 Sep 1995 08:02:54 GMT
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Date: Sun, 24 Sep 1995 20:50:49 GMT
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In article <4433be$org@comet.magicnet.net>,
 craigr@magicnet.net (Craig H. Rogers) writes:
>
>   I have an old Sony front projection set that i have had for years.
>   It hadn't been plugged in since 1991 and I plugged it in two weeks
>   ago, it fired up ok and I focused and converged the picture fine.
>   It worked ok for the last two weeks and then I left it on for a few
>   hours the other day, and coming home I saw the picture had shrunk
>   horizontally to about 75% of the screen size and the focus (electronic)
>   was a bit fuzzy and of course the convergence went out also.  I do
>   not have much if any experience with TV's other than owning a BarcoData
>   that was the greatest set at blowing up flybacks, quads, and splitters.

Was it stable at this reduced size?  No jitters that might indicate
a bad connection?  Does whacking it have any effect?  Some other possibilities:
bad capacitor or power supply problem.

>   I haven't called Sony yet to see if they would still happen to have
>   a schematic, I shall do that Monday, unless someone here knows of
>   a place to call for out-of-production schematics.  What I wish to
>   know is the probably cause of this problem, why it occured, and 
>   what to expect as far as repair and future problems.  I would have
>   assumed (probably incorrectly) that the horizontal deflection was low
>   due to some loss in the HV circuit, possibly leaky/going bad quad?

This is a possibility but such a fault would usually produce other
symptoms like blown fuses or fried transistors.

>   The only other problem that I forsee other than being ignorant is
>   attempting to probe the HV circuit (if necessary).  I have a Fluke
>   80K-6 HV probe (6kV PK MAX) connected to my Fluke 87, but that's about
>   the limit of it.  I hope I do not have to purchase a 40KV+ probe for
>   this attempted repair, I am sure that would not be cost effective.

There will probably be no need to probe the HV.

However, I do hope you are aware of the safety issues
involved in probing something like a TV - especially a projection TV.
I will include them below.

>   I would have taken to a real tech and have them repair it, but after
>   paying for replacement quads, spitters, etc for the Barco at outrageous
>   prices, I would just like to give myself "a second opinion" as to
>   possible problems.  Thank you very much.

If the only problem is a reduced horizontal size, then you probably have
a bad connection, dried up capacitor, or low power problem.

I don't know if Howard SAMs has service info for your set but that would
be the first place to check - your local large public library or an
electronics distributor.

--- sam

General Safety Guidelines when working on line powered equipment including:
        TVs, monitors, and microwave ovens.

These guidelines are to protect you from potentially deadly electrical shock
hazards as well as the equipment from accidental damage.

Note that the danger to you is not only in your body providing a conducting
path, particularly through your heart.  Any involuntary muscle contractions
caused by a shock, while perhaps harmless in themselves, may cause collateral
damage - there are many sharp edges inside this type of equipment as well as
other electrically live parts you may contact accidentally.

The purpose of this set of guidelines is not to frighten you but rather to
make you aware of the appropriate precautions.  Repair of TVs, monitors,
microwave ovens, and other consumer and industrial equipment can be both
rewarding and economical.  Just be sure that it is also safe!

* Don't work alone - in the event of an emergency another person's presence
  may be essential.

* Always keep one hand in your pocket when anywhere around a powered
  line-connected or high voltage system.

* Wear rubber bottom shoes or sneakers.

* Wear eye protection - large plastic lensed eyeglasses or safety goggles.

* Don't wear any jewelry or other articles that could accidentally contact
  circuitry and conduct current, or get caught in moving parts.

* Set up your work area away from possible grounds that you may accidentally
  contact.

* Know your equipment: TVs and monitors may use parts of the metal chassis
  as ground return yet the chassis may be electrically live with respect to the
  earth ground of the AC line.  Microwave ovens use the chassis as ground
  return for the high voltage.  In addition, do not assume that the chassis
  is a suitable ground for your test equipment!

* If circuit boards need to be removed from their mountings, put insulating
  material between the boards and anything they may short to.  Hold them in
  place with string or electrical tape.  Prop them up with insulation sticks -
  plastic or wood.

* If you need to probe, solder, or otherwise touch circuits with power off,
  discharge (across) large power supply filter capacitors with a 2 W or greater
  resistor of 100-500 ohms/V approximate value (e.g., for a 200 V capacitor,
  use a 20K-100K ohm resistor).  Monitor while discharging and/or verify that
  there is no residual charge with a suitable voltmeter.  In a TV or monitor,
  if you are removing the high voltage connection to the CRT (to replace the
  flyback transformer for example) first discharge the CRT contact (under the
  insulating cup at the end of the fat red wire).  Use a 1M-10M ohm 1W or
  greater wattage resistor on the end of an insulating stick or the probe
  of a high voltage meter.  Discharge to the metal frame which is connected
  to the outside of the CRT.

* For TVs and monitors in particular, there is the additional danger of
  CRT implosion - take care not to bang the CRT envelope with your tools.
  An implosion will scatter shards of glass at high velocity in every
  direction.  There is several tons of force attempting to crush the typical
  CRT.  Always wear eye protection.

* Connect/disconnect any test leads with the equipment unpowered and
  unplugged. Use clip leads or solder temporary wires to reach cramped
  locations or difficult to access locations.

* If you must probe live, put electrical tape over all but the last 1/16"
  of the test probes to avoid the possibility of an accidental short which
  could cause damage to various components.  Clip the reference end of the
  meter or scope to the appropriate ground return so that you need to only
  probe with one hand.

* Perform as many tests as possible with power off and the equipment unplugged.
  For example, the semiconductors in the power supply section of a TV or
  monitor can be tested for short circuits with an ohmmeter.

* Use an isolation transformer if there is any chance of contacting line
  connected circuits.  A Variac(tm) is not an isolation transformer!
  The use of GFCI (Ground Fault Circuit Interrupter) protected outlet is a
  good idea but will not protect you from shock from many points in a line
  connected TV or monitor, or the high voltage side of a microwave oven, for
  example.  A circuit breaker is too slow and insensitive to provide any
  protection for you or in many cases, your equipment.  These devices may
  save your scope probe ground should you accidently connect it to a live
  chassis, however.

* Don't attempt repair work when you are tired.  Not only will you be more
  careless, but your primary diagnostic tool - deductive reasoning - will
  not be operating at full capacity.

* Finally, never assume anything without checking it out for yourself!
  Don't take shortcuts!

 //////////////////////////////////////////////////////////////////////////////

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From: grohe@galaxy.nsc.com (Paul Grohe)
Subject: Re: ecg semiconductor crossreference
X-Nntp-Posting-Host: mil
Message-ID: <DFH9qG.Bqw@berlioz.nsc.com>
Sender: news@berlioz.nsc.com (UseNet News account)
Organization: National Semiconductor
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Mime-Version: 1.0
Date: Mon, 25 Sep 1995 20:18:15 GMT
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In article <44062n$m08@ixnews3.ix.netcom.com>, gabriel lara  says...
>
>is phillips ecg semiconductor cross reference or similiar program in
>share ware available on disk??

Yes, and believe it or not, AOL actually has somthing usefull...

If you have Access to AOL (10 free hrs???) look in the:

	COMPUTING -> SOFTWARE SEARCH and search for NTE

 
---------- Description clipped from AOL search form -----------------

File:  NTE.ZIP (2037627 bytes) 
DL time (14400 baud): < 37 minutes
Download count: 594

AUTHOR:    NTE Electronics and Cybersoft Inc.
EQUIPMENT: Hard Drive w/3 megs free, HD Floppy for install, Mouse 
recommended
NEEDS:     An UnZIPing Program

Keywords:  Cybersoft, Electronics, Parts, Catalog, Relay
Type:      Freely Distributed

Version:   01/01/92

A cross referenced database/catalog of electronic components from NTE 
Electronics. Search for either relays or semiconductors. Give entire 
Industry Device number (ECG number) or partial number. The program 
displays the component (or a list of all matching companents if a partial 
number is given). The Industry Device number, NTE Electronics device 
number, and a brief description/comment are shown. Example: when 
searching for partial relay number 121, 59 entries were listed. One was:

     Industry #HE-721A1210, NTE #R57-ID.5-12D, Described as- 
     SPST-NO 0.5A DC 12V DIP/Clamp Diode

Information can be viewed onscreen or printed. Listings of NTE sales 
offices are included. Online help is available and the program is mouse 
aware.

Note: After downloading, copy all files except NTEPAC1 to a high density 
floppy. Copy NTEPAC1 to a second HD floppy. Put the first floppy in the 
drive, change to that drive and type INSTALL. When asked, change to the 
second disk. The program will be installed to C:\NTE unless directed 
elsewhere. If you don't have a HD floppy but still want to use the 
program, you can install it from a subdirectory on your hard drive using 
the DOS SUBST command prior to running install (SUBST A: C:\DIR where DIR 
is the name of the directory you will install from. You should still tell 
install that A: is the source. Remember to SUBST A: A: when done.).

To run, enter: NTE

Documentation: Within the program

--------- Back to me ----------------------------------

You now have 9.5 hrs left..

Regards,
Paul Grohe
---------------------------------------------------------------
 Paul Grohe                     National Semiconductor Corp.
 Sr. Electronics Technician     2900 Semiconductor Drive
 New Products Engineering Group Mail Stop C2693
 Email:  grohe@galaxy.nsc.com   Santa Clara, CA. 95052-8090 USA
 (408) 721-7389 Tel             NSC datasheets online at:
 (408) 721-2513 Fax             http:\\www.nsc.com\
- Ethernet (n): something used to catch the etherbunny 
Press any key to continue or any other key to quit...
---------------------------------------------------------------

 //////////////////////////////////////////////////////////////////////////////

Article 16378 of sci.electronics.repair:
Path: cs.utk.edu!gatech!news.mathworks.com!zombie.ncsc.mil!simtel!news.sprintlink.net!dfw.nkn.net!usenet
From: Jeff Luebke <jeff@plano.com>
Newsgroups: sci.electronics,sci.electronics.repair
Subject: Re: WTB IRFP350, IRFP350, IRF740
Date: 7 Oct 1995 17:09:04 GMT
Organization: Plano Components
Lines: 16
Message-ID: <456c7g$gud@dfw.nkn.net>
References: <454u75$qmk@charles.cdec.polymtl.ca>
NNTP-Posting-Host: fastlane.net
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 1.22 (Windows; I; 32bit)
To: bassman@step.polymtl.ca
Xref: cs.utk.edu sci.electronics:151583 sci.electronics.repair:16378

We can help you with mosfets as well as other semiconductors considered hard 
to locate.We are semiconductor brokers located in the Dallas Texas area. 
Contact us via email,fax or phone, indicating your quantities required, your 
approved manufacturers and any other specific requests and we will follow 
thru...

The IRFP350's are tougher to locate than the 740's...but we should be able 
to locate at least small quantities on both.
Feel free to contact us with any questions, or comments

Thanks

Jeff Luebke
Plano Components
jeff@plano.com
http://www.plano.com/homepages/jeff/plano
214-516-0873 voice
214-423-3790 fax


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
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Organization: Microtrader Canada
Lines: 22
Message-ID: <496247$19k@aahz.magic.mb.ca>
References: <4934e5$9km@buffnet2.buffnet.net>
To: cyberman@buffnet.net
Date: 25 Nov 1995 03:21:43 GMT
From: "Brent Crighton, Microtrader Canada" <microt@magic.mb.ca>
Subject: Re: vt220 whine poof no image :)

I hate to tell you but that means the high voltage power supply
Just fried.

We can fix for $75.00 but cheaper to send you replacement used, 
warrantied terminal for $85.00

-- 
Brent Crighton, Owner

MICROTRADER Canada
Preowned Computer Systems and Parts
2229 Henderson Highway
Winnipeg, Manitoba, 
Canada

Voice....204-339-3999
Fax......204-334-6599
Direct...204-227-4089
www......http://www.magic.mb.ca:80/~microt/
email....microt@magic.mb.ca

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
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      !news-peer.sprintlink.net!uunet!in3.uu.net!en.com!usenet
Message-ID: <55j104$9ur@antares.en.com>
Date: Sun, 03 Nov 1996 23:58:43 GMT
From: ncd@en.com
Newsgroups: comp.terminals
Subject: VT220 repairs

  We repair VT220 terminals

  $50 flat rate repair for the monitor

  $25 flat rate repair for the keyboard

  Warranted 90 days

   E-mail  ncd@en.com  or call 216-953-4488    John

[northern Ohio]

 //////////////////////////////////////////////////////////////////////////////

Article 5958 of comp.terminals:
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From: edpaolo@planet.net (E. Paolo)
Newsgroups: sci.electronics.repair,comp.terminals,sci.electronics.components
Subject: Looking for LH-2440 video/chroma module
Date: 28 Jun 1996 17:50:55 GMT
Organization: Planet Access Networks - Stanhope, NJ
Lines: 13
Message-ID: <4r161v$gpf@jupiter.planet.net>
NNTP-Posting-Host: saturn.planet.net
Keywords: LH-2440
X-Newsreader: TIN [version 1.2 PL2]
Xref: cs.utk.edu sci.electronics.repair:28678 comp.terminals:5958 sci.electronics.components:6126

	The LH-2440 chroma video module used on the Tektronix monitors.
This part is not made anymore and On-line Tech has it bit with a large
min. qty amount.
	Have checked CCS, MCM, DALBANA and Allied.
	If anyone who use to repair the Tektronix monitors, who might have
a one of thes modules for sale, contact me.
Or if you know of a source of these modules made by Nat. Semi., who doesn't
have a pin/pin replacement for these, let mw know. 


                                EdDataFix
                        edpaolo@saturn.planet.net
				
 //////////////////////////////////////////////////////////////////////////////


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Newsgroups: tn.computing,tn.general,vu.general,misc.for-sale.mac,
            comp.sys.mac.hardware.video,comp.sys.hardware.misc,
            misc.forsale.computers.mac,misc.forsale.computers.monitors
            misc.forsale.computers.mac-specific.systems,
Date: Sun, 23 Jun 1996 00:42:59 -0400
Message-ID: <31CCCB53.12A0@ix.netcom.com>
References: <4q6iaj$fmn@news.vanderbilt.edu>
NNTP-Posting-Host: frd-md1-16.ix.netcom.com
To: flackcj@ctrvax.vanderbilt.edu
From: "D. M. West" <don14@ix.netcom.com>
Subject: Re: Repair of Mac Monitor?  -- Help needed


I've worked on two of those that had a shorted degaussing coil. That 
would blow a fuse thats soldered on the cca. First find the degauss coil 
connection and remove, then solder fuse holder accross blown fuse, snap 
in new fuse. If it comes up, the colors may be a mess. If you don't have 
acess to a hand held degauss coil, a local TV shop would have one. Only 
takes about two min to degauss. Do't place near other strong electrical 
feild and things sjould be ok, but may need degaussing every once in a 
while. Could be another problem, but this fix is easy to try.

Don

 //////////////////////////////////////////////////////////////////////////////

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Date: Sun, 25 Aug 1996 13:52:18 -0700
Organization: Island Net in Victoria, B.C. Canada
Message-ID: <3220BD02.2986@IslandNet.com>
References: <4vp455$ol4@juliana.sprynet.com>
NNTP-Posting-Host: i2-133.islandnet.com
From: Jan Skirrow <dma@IslandNet.com>
Subject: Re: looking for monitor schematics and parts

tettra@sprynet.com wrote:
> 
> Greetings
> 
> I am looking for schematics for any and all types of monitors.  I am
> also looking for parts for any and all monitors (CRTs analogs and
> such).  If anyone knows of any companys who sell these schematics and
> parts please let me know
> 
> Thanks in advance
> 
> Jeff

MI Technologies has a large range of monitor schematics for sale.
Pricey, but there may be little other option!

Fax: 513-339-6344 Tel: 513-335-4560

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair
Path: cs.utk.edu!news.msfc.nasa.gov!newsfeed.internetmci.com!in2.uu.net
      !mint.net!news
Date: Sat, 07 Sep 1996 22:24:56 -0400
Organization: Digiphonics Audio Laboratories
Message-ID: <32322E78.18F0@mint.net>
References: <322FBE72.7081@pacbell.net>
Reply-To: bryboe@mint.net
NNTP-Posting-Host: dialup-b-9.mint.net
From: brian leeman <bryboe@mint.net>
Subject: Re: Sony Model 13TR25 - 13 inch receiver interminent tuner


w6cjw@pacbell.net wrote:
> 
> Would like to know if any users have discover why the tuner or tv signal
> fails to work until the set has been on for about 10 minutes. This
> problem shows up on the VHF channels - the UHF channels will work. A
> number of the same vintage sets are starting to show the same problem.
> Any suggestions would be most welcome.


I have run into a few of these...

In every case it has been due to one of the grounding "fan" leads that
runs from the PCB to the metal case having a cold joint.

It has always been the lead that fastens to the top of the case directly
to the left of the AGC trimmer (looking at the trace side).

These problems are gravy for techs, but it is a shame how poorly Sony
executes the manufacture of their consumer electronics. Talk about mass
produced junk...

Sorry for the rant, but if you work on this stuff, you hafta agree!!

Hope this helps & good luck!!

Brian

 //////////////////////////////////////////////////////////////////////////////

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Date: 8 May 1997 18:17:57 GMT
Organization: Research Applications Program, NCAR, Boulder, CO  USA
Message-ID: <5kt5cl$f12$1@ncar.ucar.edu>
References: <33666b7c.33635335@207.51.163.4>
            <336bc088.1130740@netnews.worldnet.att.net>
            <dainey-0605970001520001@hsh1-44.flash.net>
NNTP-Posting-Host: 128.117.192.15
From: ren@rap.ucar.edu (Ren Tescher)
Subject: Re: HP Service Stinks (was Re: HP 550C -or- Even tanks need repair!)


In article <dainey-0605970001520001@hsh1-44.flash.net>,
 "Diane L. Roskar" <dainey@flash.net> writes:
>
> [snip]
> This is not very good service at all!!!

> An example of good product service is given by Sony: I can still get service
> & repair parts for my 7 year old Sony Hi8 Video camera, over the phone -- as
> an end-user consumer.


You're saying Sony has great product service?

You've obviously never tried to get parts/schematics/advice on any of
the many Computer Monitors they've entered into Non-Disclosure Agreement
(NDA) with Computer OEM's (e.g. Sun, SGI).

I'm talking Sony models CPD-1790, GDM-1662 & GDM-1604 in particular.

In that case, only a few companies approach the Sony Suck Factor, and
probably no other manufacturer exceeds the SSF standard set by Sony.

The real rip is, none of the OEM's are capable of repairing the
Sony Monitors either!  They just replace them.

Please, use some other, 'realistic' example when referring to good
customer service.

-- 
Ren

 //////////////////////////////////////////////////////////////////////////////

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References: <199609301538.KAA15960@plains.nodak.edu>
Sender: news@spcuna.spc.edu (Network News)
Organization: St. Peter's College, US
Date: Mon, 30 Sep 1996 20:27:05 GMT
Message-ID: <1996Sep30.162705.1@spcvxb.spc.edu>
From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.)
Subject: Re: Opening a VT220


In article <199609301538.KAA15960@plains.nodak.edu>,
 Todd Enders - WD0BCI <enders@plains.nodak.edu> writes:
>
>      So, everything external has been checked, now I have to get inside the
> thing.  Trouble is, I've removed the obvious screws, the not-so-obvious 
> screws, and a few others.  Still can't make the bloody thing come apart.
> Now, I'm sure there's a neat trick involved, or I'll need something like
> the case-cracking tool for the old Macintoshes, but there *has* to be a
> way inside the blasted thing!

  There are 3 screws hidden under plastic caps, 1 on the back and 2 on the
bottom. The caps are maybe 3/8" in diameter and are recessed into a plastic
ridge. I use one of the tiny green-handled Xcelite screwdrivers to pry 'em
out (I don't know if there's a better way) and then use a regular Philips
screwdriver on the 3 screws that are revealed.

  Obligatory caution note: Dangerous high voltages inside - trained service
personnel only.

	Terry Kennedy		  Operations Manager, Academic Computing
	terry@spcvxa.spc.edu	  St. Peter's College, Jersey City, NJ USA
        +1 201 915 9381 (voice)   +1 201 435-3662 (FAX)

 //////////////////////////////////////////////////////////////////////////////

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    !umass.edu!nic.umass.edu!wilde.oit.umass.edu!not-for-mail
Date: 1 Oct 1996 22:06:31 GMT
Organization: University of Massachusetts, Amherst
Message-ID: <52s4l7$mo5@nic.umass.edu>
References: <199609301538.KAA15960@plains.nodak.edu>
            <52pd60$h4r@mars.hyperk.com>
From: asvirsky@wilde.oit.umass.edu (Alexander R Svirsky)
Subject: Re: Opening a VT220


If the keyboard doesn't light and the CRT does not fire up, it is 
possible that the problem is as simple as a broken power switch.  I have 
had 3 VT220's with bad power switches.  Swapping switches out of VT220's 
with bad tubes or boards always worked for me.

Good luck,
Alex

-- 
Alexander Svirsky    N1PRW                  University of Massachusetts
asvirsky@student.umass.edu                            Amherst

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: vmsnet.pdp-11
Path: cs.utk.edu!cssun.mathcs.emory.edu!gatech!csulb.edu!news.sgi.com
      !howland.erols.net!EU.net!usenet2.news.uk.psi.net!uknet
      !usenet1.news.uk.psi.net!uknet!uknet!lyra.csx.cam.ac.uk!ard12
Date: 30 Sep 1996 18:56:54 GMT
Organization: University of Cambridge, England
Message-ID: <52p55m$mqu@lyra.csx.cam.ac.uk>
NNTP-Posting-Host: club.eng.cam.ac.uk
From: ard12@eng.cam.ac.uk (A.R. Duell)
Subject: Re: Opening a VT220

shoppa@alph02.triumf.ca (Tim Shoppa) writes:

>>     So, everything external has been checked, now I have to get inside the
>>thing.  Trouble is, I've removed the obvious screws, the not-so-obvious 
>>screws, and a few others.  Still can't make the bloody thing come apart.
>>Now, I'm sure there's a neat trick involved, or I'll need something like
>>the case-cracking tool for the old Macintoshes, but there *has* to be a
>>way inside the blasted thing!  The '220 is the console terminal for my 11/10,
>>and I don't have anything else short of an old DECwriter that'll do current
>>loop, so I pretty well need the '220 back on line.  Any help would be greatly
>>appreciated!  Many thanks!!!

>Screws?  As I recall, you only have to remove one screw.  It's on the

No, you're thinking of the VR201 (which has only 1 screw on the rear). 

The VT220 (I've opened a lot of them) is held together by 3 screws, all 
covered by those white plastic domes. One on the rear and two on the 
bottom, I think.

You unplug all the cables, stand the thing on its front, flick off the 
domes, undo the screws, and pull the shell off.

>back, centered left-right, near the top, and usually covered by a
>white plastic dome which you have to pop off.  The cover now ought to
>slide right off the rear.

If you're opening a VR201 (the PRO/DECmate/Rainbow mono monitor), don't 
forget to extend the leg fully before you start. Otherwise the case will 
not come off.


>Sure beats the plastic "snap" connectors used to hold the top of
>a VT100 on!  Very few of those have survived intact over the
>course of nearly 20 years...  mainly because of techs who didn't
>properly know how to disengage them.

Those infernal things are the invention of the Devil :-(. They're used in 
some other DEC devices as well - the LA100 series springs to mind. I'd 
much prefer proper screws...

Oh, and if the original poster can't fix his VT220, there are TTL level
serial I/O signals on the 11/10 connector where you'd expect them. A 
little kludge using a MAX232 should let you hook up an RS232 terminal. 

Or, of course, you could search for the orignal IBM Async card, which, 
amazingly, had 20mA loop circuitry...


>Tim. (shoppa@triumf.ca)

--
-tony
ard12@eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill

 //////////////////////////////////////////////////////////////////////////////

  [regarding the Macintosh case-cracking tool]

Newsgroups: alt.folklore.computers
Date: 10 Apr 1997 08:52:20 GMT
Message-ID: <5ii9o4$sbn@reader.seed.net.tw>
From: dski@cameonet.cameo.com.tw
Subject: Re: Opening a Mac (was Re: IBM PC vs. Apple ca. 1981)

Jay R. Ashworth (jra@scfn.thpl.lib.fl.us) wrote --
>
> Along with square bits, which have a name, too.  "Robertson"?

Right on the button. Full name: square-recess bits. Also called Robertson
and Scrulox tips.

Salvaged a pristine McMaster-Carr Supply Company catalog from the trash
when the company next door moved out. "Serving Industry Since 1901" -- I
can believe it. Nowhere do they say what kind of supply company M-C is.
They hardly need to, with 2,963 pages of, of... *stuff*.

Dan Strychalski


 //////////////////////////////////////////////////////////////////////////////

  [here are other people's recollections about the Mac tool]

Newsgroups: alt.folklore.computers
Date: 8 Apr 1997 18:33:44 GMT
Message-ID: <01bc444c$6cdc2020$0f02000a@grant>
From: Grant Gischer <grantg@memes.com>
Subject: Re: Opening a Mac (was Re: IBM PC vs. Apple ca. 1981)


> : In article <33458224.0@131.162.2.91>, 016958j@news.acadiau.ca (Kenneth
Jamer) writes:
>
> : >Torx screwdrivers ... hmm should have 10(ish) points and a flat top..
> : >cause I had a Buick that required one to change the headlamps. Had a
> : >heck of a time finding one, eventually found a whole set of them
> : >4 different sizes (and maybe different point counts ?). Could it be the
> : >same thing?
> : *10* points? My husband just showed me a couple of these (different sizes),
> :  and
> : his have six points. (baffled look)
> : Do Torx screwdrivers come with different point counts? I am basically
> : totally clueless
> : about most tools. My husband says that they're all six-point (but he
> : does tend to be a
> : bit arrogant (smile)).
>
> <*sheepish grin*>
> umm six points is a possibility, When I was posting I remebered the T-10
> designator in a slightly strange way. I don't have any around at the
> moment, but the more people say, the more Im sure I was mistaken.
>

I just got out my set (it has 8 sizes), and they all have six points. (Not
to be confused with a hex/Allen wrench, which has six faces)

It looks like a star of David, which I will attempt to graphically
illustrate here:

          /  \
    _____/    \_____
    \              /
     \            /
     /            \
    /____      ____\
         \    /
          \  /

Hope that helps.
-- 
grantg@memes.com
http://www.memes.com/~grantg
Forsale Page: http://www.memes.com/~matt/compfs.html

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: alt.folklore.computers
Message-ID: <5ib7h9$vek@flood.weeg.uiowa.edu>
Date: 7 Apr 1997 16:31:37 GMT
From: "Douglas W. Jones,201H MLH,3193350740,3193382879"
      <jones@pyrite.cs.uiowa.edu>
Subject: Re: Opening a Mac (was Re: IBM PC vs. Apple ca. 1981)

From article <5ib4f0$ap4@tor-nn1-hb0.netcom.ca>,
by seward@netcom.ca (John Savard):
>
> Bought an original Mac - screen is dead - for $15 at a thrift shop.
> Can't find a long enough Torx in any hardware store - or, since hex
> Torx bits are available, a slim enough holder for them.

Bought a broken Mac SE (screen is dead) for $5 at a surplus outlet.
Found another SE in a trash can, stripped of memory and disk drives.
Found a "mac cracker" (Torx wrench) in pile of tools discarded by
computer maintenance group.  Found a diskette copy of MAC-OS 7.1 still
in shrink-wrap at a surplus outlet for $5.

The mac cracker is a standard hex Torx bit rammed into a piece of
thin-wall steel tube with a flat blade welded to the hind end to make
a T-shaped handle.  The ramming operation distorted the end of the tube
to the hex shape of the but end of the bit.  The flat handle is also
useful in "cracking" a mac because you can set the edge of it in the
crack between the front and back halves of the case

Net result?  One working and useful Mac SE for my son, for almost nothing.
Plus a spare power supply and motherboard.  The dead screen was caused
by a bad picture tube -- no vacuum.

                                Doug Jones
                                jones@cs.uiowa.edu

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: vmsnet.pdp-11
Path: cs.utk.edu!gatech!csulb.edu!news.sgi.com!news.mathworks.com
      !www.nntp.primenet.com!nntp.primenet.com!howland.erols.net!EU.net
      !usenet2.news.uk.psi.net!uknet!usenet1.news.uk.psi.net!uknet!uknet
      !warwick!lyra.csx.cam.ac.uk!ard12
Date: 1 Oct 1996 16:27:58 GMT
Organization: University of Cambridge, England
Message-ID: <52rgqe$gvu@lyra.csx.cam.ac.uk>
References: <199609301538.KAA15960@plains.nodak.edu>
From: ard12@eng.cam.ac.uk (A.R. Duell)
Subject: Re: Opening a VT220


Todd Enders - WD0BCI <enders@plains.nodak.edu> writes:
>
>     After loaning out my venerable VT220 for some work-related activities,
> it no longer does anything when turned on.  Checked the fuse, and it was OK,
> plus, mains voltage appeared at the fuse socket.


I assume you have a keyboard connected, and that the LED's on that don't 
blink when you turn the terminal on. If that's the case, then it sounds 
like a power supply problem.

From what I recall, the VT220 PSU is a fairly simple thing with a line 
frequency transformer bolted to the chassis feeding low-voltage AC to the 
video board. When you've got the cover off, I'd check the output(s) of 
the transformer first, and then check the power pins of the chips on the 
digital board. I don't have the VT220 printset (does such a thing 
exist?), but I never had any problems fixign them.

>Todd     enders@plains.nodak.edu

--
-tony
ard12@eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: alt.folklore.computers
Path: utkcs2!stc06.ctd.ornl.gov!fnnews.fnal.gov!news.imsa.edu!chi-news.cic.net
      !arclight.uoregon.edu!su-news-hub1.bbnplanet.com
      !cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!worldnet.att.net!uunet
      !in2.uu.net!192.89.123.24!nntp.inet.fi!news.sci.fi!usenet
Date: Sun, 16 Mar 1997 06:35:46 GMT
Organization: Scifi Communications International
X-Contact: helpdesk@sci.fi, +358 3 2899111, http://www.sci.fi/
Message-ID: <333681ee.1296983714@news.sci.fi>
References: <5ge6hr$l3b@reader.seed.net.tw>
NNTP-Posting-Host: ccclv.dyn.sci.fi
From: keinanen@sci.fi (Paul Keindnen)
Subject: VT-220 (Was: Pre-1988 Windows ECS)


dski@cameonet.cameo.com.tw wrote:

>From dski@cameonet.cameo.com.tw (sound familiar?) came the query --
>
>> Anyone know what Windows used for an extended character set before
>> ISO 8859-1 came along?
>
>Well, I seem to have found an answer to my own question -- in the same
>German article I asked folks to translate part of a few months ago. I
>don't think I thanked everyone then, so I now extend thanks to all. I
>daren't make another request, so I'll just post the relevant passage.
>Here are some URLs where the full article can be found:
>
>http://www.nadir.org/NA/WebEntry/8859-de.txt
>http://www.sax.de/text/README.umlauts
>http://vops2.avl.co.at:8001/www/faq/de-usenet-umlaute.txt
>
>And here's the part that mentions the original Windross charset:
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>Im Jahre 1981 kam der IBM PC mit einer 8-bit Zeichenkodierung heraus.
>Leider schienen die Entwickler bei der Reihenfolge der Zeichen
>gewuerfelt zu haben. Das Ergebnis: die IBM Codepage 437.
>
>Im Jahre 1982 wurden die ersten DEC VT220 und VT240 auf den
>Markt gebracht. Die hatten einen Vorlaeufer von ISO 8859-1
>im Einsatz: DEC MCS (Multinational Character Set).


All the documentation that came with the VT-220 has a copyright date
for the first edition as August 1983, so the 1982 as the release year
for VT-220 and VT-240 sounds a bit early.

In addition to the MCS character set the VT-220 had some other
oddities in the serial line interface. Due to the signal and
protective ground arrangement, it produced much more ground loop
problems than the VT-100. The serial line transceivers were according
to RS-423, which had a lower output voltage swing than RS-232, but
still within the input specification for RS-232, so the terminal was
compatible with older equipment using the original RS-232
transceivers. Some sources claimed that the RS-423 was the unbalanced
version of the symmetrical RS-422, but I have newer seen the
specifications for both of these standards.

Anyway, the RS-423 transceivers on early VT-220s were quite fragile,
since all but one of our VT-220 failed within the warranty period.
Apparently this was a common problem, since the DEC field service
engineer always first installed a socket and then inserted the
transceiver. After a few visits, he gave us a tube of those
transceivers to be used, if the repaired terminal would once again
failed. We were quite disappointed that the last one from this batch
did not fail during the warranty period, to get the socket installed.
Yes, you guessed, that one failed a month after the warranty period,
so it was time to fire up the soldering iron, fortunately, there were
some chips left in the tube we got earlier. Later versions of the
VT-220 had protection diodes cludged at the factory around and above
the transceiver chips. Does anyone the reason for the high mortally
rate for these transceiver chips or were they just badly designed ?

Paul Keinanen


 //////////////////////////////////////////////////////////////////////////////

Path: utkcs2!stc06.ctd.ornl.gov!cs.utk.edu!gatech!news.mathworks.com!mvb.saic.com!info-vax
From: BENCHABANE@IST.CERIST.DZ
Newsgroups: comp.os.vms
Subject: Re: LK201 keyboard failures
Message-ID: <01IGLS2DOW5U002207@IST.CERIST.DZ>
Date: Mon, 17 Mar 1997 09:44:27 +0000 (GMT)
Organization: Info-Vax<==>Comp.Os.Vms Gateway
X-Gateway-Source-Info: Mailing List
Lines: 29

Hello Dennis,

Inside the LK201 there is a printed circuit (field service module) :
part number : 54 16941 or 54 15148.

depending of the version of this module you have differents integrated
circuits,
resistors , capacitors etc...

on the 1st part number , there are 3 IC's.
on the th 2nd : 9 IC's etc... 2 of them make the communication between the KB
and the logic board inside the VT:  UA (or MC) 9636  for transmit
                                    UA (or MC) 9639  for receive.

on this board there is a voltage reglator : MC 7805 which deliver + 5V.

The flat cables (from this module to the keys map) are not easy to remove
or replace...so be carefull.

The failure is not necessary on the module; the failure can de caused by the
keys map if one key  is detecded down during the power on.

I hope this helps.

But I am looking for the error code displaying by the LK201 LED's.....

-- 
Lies BENCHABANE                             E-mail: benchabane@ist.cerist.dz

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: stc06.ctd.ornl.gov!news.er.usgs.gov!jobone!newsxfer3.itd.umich.edu
      !cpk-news-hub1.bbnplanet.com!su-news-hub1.bbnplanet.com
      !news.bbnplanet.com!csn!nntp-xfer-1.csn.net!csn!nntp-xfer-2.csn.net
      !symbios.com!news
Date: Mon, 14 Apr 1997 10:51:55 -0600
Organization: Symbios Logic
Message-ID: <335260AB.6668@symbios.com>
References: <334D08F7.705A@mail.bellsouth.net>
NNTP-Posting-Host: jkrantzpc.co.symbios.com
From: Joe Krantz <joe.krantz@symbios.com>
Subject: Re: VT220 - have many giving "keyboard error code 4" - typical causes?


Paul V. Kretzschmar <piper95@mail.bellsouth.net> wrote:
>
> Hey,
>
> Got a ton of used vt220's that
> I have to get running again, most keyboards
> giving  error code 4....  suspect keyboard
> membranes may be bad as they were lying on
> top of one another for awhile.
>
> Anyone have input on this error, are keyboard
> fixable, maybe open-up and clean keybd interiors??


It could be keys that are stuck down/jammed together,
or bad cable/connection between the monitor and the
keyboard (check *both* ends), or it could be the
monitor/system end - find one 'system' that passes
the test, and cycle all keyboards through that
'system'.

You can try blowing the dust out of them with a high
pressure air hose, or turn them upside down, and
'bang' them a bit.

Also, try opening up one of the failing units and
see if someone has spilled anything into it (like
coffee or coke...).

        Joe

P.S.


One more thought, if you pop off any of the keys,
be careful of the larger keys, some contain one
or more springs that can be hard to find if you
aren't expecting them.

        Joe

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: vmsnet.pdp-11
Path: utkcs2!stc06.ctd.ornl.gov!news.he.net!feta.direct.ca!newsfeed.direct.ca
      !cpk-news-hub1.bbnplanet.com!cam-news-hub1.bbnplanet.com
      !news.bbnplanet.com!news-xfer.mccc.edu!mars.njcc.com!not-for-mail
Message-ID: <yRp4quoWWtWL079yn@pluto.njcc.com>
References: <199709050437.AAA07232@endor.harvard.edu>
Organization: NJ Computer Connection for Astro Imaging Systems
From: hjohnson@pluto.njcc.com (Herbert R Johnson)
Date: Sun, 07 Sep 1997 19:21:32 -0400
Subject: Re: power supply sadness


In article <199709050437.AAA07232@endor.harvard.edu>,
Dan Lanciani <ddl@deas.harvard.edu> wrote:
*>
*>So, an hour later I have the thing apart (hate those locktighted standoffs)
*>and I've found the shorted cap (after a few wrong guesses).  I replace the
*>cap, put it back together, and power up.  All the voltages are right.  Then
*>the smoke starts billowing out.  Shut it off, take it all apart again,
*>nothing seems burned.  Power up again and the voltages are still fine.
*>No more smoke.  Very frustrating.  I assume some other cap decided to die
*>but couldn't quite maintain its short. :(  It's harder to troubleshoot a
*>working supply and there are a lot of caps in this box...


I have similar problems with S-100 equipment from the same era. It's
simple physics: tantalum-based capacitors, for example, grow "whiskers"
of tantalum over time.  As these get bigger, they eventually puncture
the dielectric and create shorts.  That's why some little capacitors
"flame on" upon powerup and create smoke, flame, etc. (Really helps
to drop the price during negotiations, incidently.)

There are other problems with electrolytics that are due to the passage
of time and heat. In the old, vacuum-tube days, it was recommended that
unused equipment be powered up from a low-voltage AC source and slowly
raised. Don't know how multi-voltage chips like old DRAMS would like that
today. Sometimes I use a Variac to power up older equipment for initial
tests.

Shorts can be detected with an ohmmeter, to the extent the rest of
the circuit doesn't appear as low resistance. I've been using a
capacitive scale on a new DVM to find shorted and undervalued
caps, with some success. THey are modestly accurate, and can measure
from tens of pF's to a few hundred microfarads.

Herb Johnson
-- 
Herbert R. Johnson                      voice/FAX 609-771-1503 day/nite
hjohnson@pluto.njcc.com                 Ewing, NJ (near Princeton) USA
                 occasional amateur electronic astronomer
               supporter of classic computers as "Dr. S-100"
   and senior engineer at Astro Imaging Systems: old photons to new bits!

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair, comp.terminals,
            biz.marketplace.services.computers
Date: Wed, 18 Feb 1998 15:32:11 -0500
From: depotdig <depotdig@gate.net>
Subject: 15 Years in WYSE Repairs!

Are your Wyse terminals acting up?
We can help!  We've got  15 years experience
repairing Wyse products.  Low, flat rates.

             DEPOT DIGITAL SERVICES
 Questions?  Call 813-881-9388 or  Email us!

 //////////////////////////////////////////////////////////////////////////////

 -------------------------

Message-ID: <PuYm1.409$pk3.591185@weber.videotron.net>
Organization: PCR
Date: Fri, 03 Jul 1998 03:46:55 GMT
From: BoB <pcr@info-internet.net>
Newsgroups: comp.terminals
Subject: wyse flyback
 
we got all kind of wyse flyback, give ys a call, jason, 514-333-1455, pcr

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.terminals
References: <3607F23B.F5618588@edgenet.net>
Message-ID: <19980923190159.04114.00000853@ng25.aol.com>
Date: 23 Sep 1998 23:01:59 GMT
From: MeOzzy <meozzy@aol.com>
Subject: Re: Keyboards!


I can sell used DEC keyboards. We do test them in the refurb. center
and test them before we ship them.

-- 
 Richard
 PMM
 Pager +1 504/929-1864


 //////////////////////////////////////////////////////////////////////////////

Date: Sun, 5 Dec 1999 15:37:03 -0000
Newsgroups: comp.terminals
Message-ID: <384a8a99@news.jakinternet.co.uk>
From: Gavin Atkinson <gavin_ng@exl.co.uk>
Subject: Wyse WY-85 needing repair

Hi,

I have a Wyse WY-85 terminal which was recovered from a pile of junk.
However it seems to have a power supply problem. I was wondering if anyone
knew of a company in england (preferably Northern England) who repair these.
Or even better, if anyone can point me to websites/locations of service
manuals etc so I can repair it. (I am able to repair it if I knew what the
problem was). Many web searches have turned up nothing sadly.

Many thanks,

Gavin.


 //////////////////////////////////////////////////////////////////////////////

Date: Sun, 5 Dec 1999 21:57:31 -0500
Newsgroups: comp.terminals
Message-ID: <384b268a.0@news3.paonline.com>
From: droid <root@localhost>
Subject: Re: Wyse WY-85 needing repair

.
>Or even better, if anyone can point me to websites/locations of service
>manuals etc so I can repair it. (I am able to repair it if I knew what the
>problem was). Many web searches have turned up nothing sadly.


Gavin,
 Wyse was notorious for using a glue which becomes conductive
over the years. it is colored yellow but becomes brown. chances
are that is the problem.i use a dental pick to scrape it off the
components. if you have an ohmeter, just touch a glob of glue
and see if you get a reading, if so that is the problem.

good luck

 //////////////////////////////////////////////////////////////////////////////

Date: Sun, 5 Dec 1999 22:17:03 -0500
Newsgroups: comp.terminals
Message-ID: <384b2b1e.0@news3.paonline.com>
From: droid <root@localhost>
Subject: Re: Wyse WY-85 needing repair

oh yeah ,one more thing ,

any monitor that is malfunctioning is suseptible to
keeping the main capacitors charged, so you
might want to check them with a voltmeter
first before doing the remove glue procedure...

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.terminals
References: <65089820.0110311908.112b2cf@posting.google.com>
  <3BE06A10.A43A33B@rcn.com> <65089820.0111031705.42f3f66f@posting.google.com>
Message-ID: <XJ6F7.49255$IR4.26911361@news1.denver1.co.home.com>
Organization: Excite@Home - The Leader in Broadband http://home.com/faster
Date: Sun, 04 Nov 2001 08:10:31 GMT
From: mroberds@worldnet.att.net
Subject: Re: Wyse 75 terminal problems

Ian Primus <ian_primus@yahoo.com> wrote:
>
>The high pitched squeal remains, and seems to be coming from the 
>black dealy that it connected to the video tube by a fat red cable
>and a suction cup.

This is the flyback transformer.  It converts the line voltage coming
into the terminal (120v or 240v) into a very high voltage for the
picture tube - on the order of 15 to 25 kilovolts.  The current is
low, but it's still enough to zap you if you put yourself across it.

>I have been trying to identify the smell, it doesn't seem to be a
>burning smell after all, it is an acrid smell, almost like the smell a
>photocopier makes.

Sounds like ozone.  Does it smell like the electric bumper cars at an
amusement park?  Usually this smell comes from sparks - in your case
the high voltage from the flyback transformer sparking to something
else, due to a loose connection or broken insulation.

>I have a knowledge of electronics, but I normally work with low 
>voltage circuits, computers, etc.

Take a look at

    http://www.repairfaq.org/

and specifically the monitor repair FAQ at

                http://an.hitchcock.org/repairfaq/REPAIR/F_monfaq.html

 [2005 mirror:  http://repairfaq.ece.drexel.edu/sam/monfaq.htm ]

There is a section in the monitor FAQ specifically about the whining
noise you have.

Good luck!

Matt Roberds

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.terminals
References: <65089820.0110311908.112b2cf@posting.google.com>
    <3BE06A10.A43A33B@rcn.com>
    <65089820.0111031705.42f3f66f@posting.google.com>
    <XJ6F7.49255$IR4.26911361@news1.denver1.co.home.com>
Message-ID: <65089820.0111041612.5a263da9@posting.google.com>
Organization: http://groups.google.com/
Date: 4 Nov 2001 16:12:50 -0800
From: Ian Primus <ian_primus@yahoo.com>
Subject: Re: Wyse 75 terminal problems

Well, I used a length of rubber hose as a stethescope and determined
that the soud is not coming from the flyback, but is in fact coming
from what appears to be a regular transformer on the left (looking
from the back) side of the board. I am assuming that this is the low
voltage transformer. I tried tapping on it and some of the surrounding
components with a pen barrel, and the noise went away. If I jiggle
something else, it will come back, and putting the cover back on it
seems to jiggle it as well, returning it to the annoying whine. Any
ideas?

Ian Primus
ian_primus@yahoo.com 


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <65089820.0110311908.112b2cf@posting.google.com>
    <3BE06A10.A43A33B@rcn.com> <65089820.0111031705.42f3f66f@posting.google.com>
Message-ID: <9s4s3u$gbq$4@dos.canit.se>
Organization: Canit Public Access, Stockholm
Date: 5 Nov 2001 02:04:46 GMT
From: Iggy Drougge <optimus@canit.se>
Subject: Re: Wyse 75 terminal problems

Ian Primus <ian_primus@yahoo.com> skrev:
:
: After a little bit of running, the wavyness went away... The high
: pitched squeal remains, and seems to be coming from the black dealy
: that it connected to the video tube by a fat red cable and a suction
: cup. Whacking the table sometimes changes the pitch of the squeal. I
: have been trying to identify the smell, it doesn't seem to be a
: burning smell after all, it is an acrid smell, almost like the smell a
: the terminal works just fine, save for the noise. It could use an
: done, and I really need the terminal. I have a knowledge of
: electronics, but I normally work with low voltage circuits, computers,
: etc. I know very little about monitors. Fortunately, I am good with a
: soldering iron, but I really don't know what I need to replace. Any
: ideas?

I've got an old terminal with the same problem (high pitched squeal). I've
been told by people experienced with CRT repair that it's the flyback
transformer which has started to decompose, resulting in certain parts
vibrating at high frequencies. The flyback is the big, unshapely thing
coated in resin, connected to the suction cup on the CRT.
One cure which might work is to encapsulate and fixate the flyback with
great amounts of glue.

-- 
/Iggy, the irregular regular

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <65089820.0110311908.112b2cf@posting.google.com>
    <3BE06A10.A43A33B@rcn.com>
    <65089820.0111031705.42f3f66f@posting.google.com>
    <XJ6F7.49255$IR4.26911361@news1.denver1.co.home.com>
    <65089820.0111041612.5a263da9@posting.google.com>
Message-ID: <FNqF7.51690$IR4.28672444@news1.denver1.co.home.com>
Organization: Excite@Home - The Leader in Broadband http://home.com/faster
Date: Mon, 05 Nov 2001 06:59:49 GMT
From: mroberds@worldnet.att.net
Subject: Re: Wyse 75 terminal problems

Ian Primus <ian_primus@yahoo.com> wrote:
>Well, I used a length of rubber hose as a stethescope and determined
>that the soud is not coming from the flyback, but is in fact coming
>from what appears to be a regular transformer on the left (looking
>from the back) side of the board. I am assuming that this is the low
>voltage transformer.

If it's a fairly good distance from the flyback, and is near where
the power cord attaches to the board, then yeah, that's probably it.

How is it attached to the board?  Sometimes they are just held down
by the solder on their leads.  Sometimes there are nuts and bolts
holding it to the board, and sometimes there are metal tabs on the
transformer frame that go through holes in the board and are bent
over.  If it's just held down by the solder you can't do much about
that, but you can tighten bolts and attempt to tighten bent tabs.
Rivets are also used; if you can't tighten them by crimping them
with pliers, try soldering the rivet in place.  Do this with the
terminal unplugged and use a big soldering gun, being careful of
nearby components.
 
Some transformers like this are made so that the laminations+coil
just slides into a stamped sheet metal frame.  You could try
crimping the frame down on the laminations with a pair of pliers
to tighten it up.  Do this with the power off and use insulated
pliers anyway.  Looking at it from the side or the top, where **
is the coil and the bar in the middle is the frame:
    ._.
--->| |<---  crimp here
  **| |**
  **| |**
  **| |**
--->|_|<---  crimp here

If it doesn't have an obvious outer frame (usually shiny) over the 
laminations (usually flat and dull), then don't do this.

If there is enough room between the transformer and the board, you
might try jamming something non-conductive (wood or plastic) in
there to quiet it down.  Or try a plastic self-locking cable tie
(zip tie) or two around the whole transformer.

If you've localized it to this transformer then you should be able
to do something to it to make the noise stop.

Matt Roberds




 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.terminals
References: <65089820.0110311908.112b2cf@posting.google.com>
    <3BE06A10.A43A33B@rcn.com>
    <65089820.0111031705.42f3f66f@posting.google.com>
    <XJ6F7.49255$IR4.26911361@news1.denver1.co.home.com>
    <65089820.0111041612.5a263da9@posting.google.com>
Message-ID: <3BE621FC.562EAA78@rcn.com>
Date: Mon, 05 Nov 2001 05:22:04 +0000
From: Jim <microsyseng@rcn.com>
Subject: Re: Wyse 75 terminal problems

Pretty good diagnostics.. everyone is pretty much on the same page on
this one.  What bothers me is the wavy lines coupled with the smell of
something overheating.. The power supply circuit is either a full wave
or a half wave rectifier circuit. If it is a full wave you will see two
distinct and separate lines of distortion slowly rolling verticle up the
screen. This will distort the font. If it's a half wave circuit you will
only see one line. What is happening, is that some component of the low
voltage supply is failing and quite posssibly repair intself temoparily
when it heats up.. Possibly the filter capacitors. That would cause a
drop in the overall DC power supply output level as there would be quite
a bit of AC ripple riding on top of the DC. It would also cause the
power transformer to heat and the insulation of the windings to break
down over time. The filter capacitors are probably electrolytic and they
dry out with time. The terminal is not exactly of new manufacture. In
fact, it's some years old.

While it's nice in theory, The repair faq's mentioned in Mroberds
response will tell you the same thing. My own experience tells me that's
whats happening.  Power transformers have a distinct smell to them when
they get hot. You might check for residue around the base of the
transformer which would indicate insulation breakdown that is leaking
through the case. Capacitors don't have to look burnt or deformed in
order to have failed or be in the process of failing. Most people just
replace them when in doubt and not in possesion of good test equipment.


 //////////////////////////////////////////////////////////////////////////////

Path: utkcs2!gatech!swrinde!mips!pacbell.com!att!cbfsb!cbnewsb.cb.att.com!wa2ise
From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: comp.terminals
Subject: VT220 display repair
Keywords: bad pot in sync circuit
Message-ID: <1991Dec28.155531.9997@cbfsb.att.com>
Date: 28 Dec 91 15:55:31 GMT
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Lines: 16

I have a VT220 terminal that had a display problem.  The image (charcters
on the screen) used to wiggle side to side from time to time.  Took the
cover off, and found that the pot marked something like "horiz hold"
seemed dirty.  When I rotated it some, the wiggle problem would clear
for a while.  Got tired of having to do this every so often, so I replaced
this pot.  No more wiggles since I did this a week ago.
BTW, when I got this terminal, the display was not horiz sync-ing at all.
Cleared that by playing with this pot.  This bad pot caused the reason
why I was given this terminal in the first place.

This pot is the one inside the display, on the left side, closest to the 
front.  You have to take the back cover off to see it.  It's just a cheap
trimpot type.  5K ohms.  4.7K will also work.  Try to measure the old
pot with an ohmeter to verify this though.

This may be all that's wrong with that VT220 sitting in the back room.

Disclaimer: proceed at your own risk.  WA2ISE


 //////////////////////////////////////////////////////////////////////////////

Path: utkcs2!emory!swrinde!mips!mips!decwrl!access.usask.ca!regina
      !mercury.cs.uregina.ca!hubich
Newsgroups: comp.terminals
Message-ID: <1992Feb25.162530.10716@regina.cs.uregina.ca>
Sender: usenet@regina.cs.uregina.ca (Usenet Admin)
Reply-To: hubich@mercury.uregina.ca (Chad D. Hubich)
Distribution: comp.terminals sci.electronics
Organization: University of Regina, Regina, Saskatchewan
Lines: 39
Nntp-Posting-Host: mercury.cs.uregina.ca
Date: 25 Feb 1992 16:25:30 GMT
From: hubich@mercury.cs.uregina.ca (Chad D. Hubich)
Subject: VT100 Repairs


	Over the years we have repaired a few DEC VT100 terminals with 
various problems.  Typically the same failures occur repeatedly in 
different machines.  Below is a short summary of some of the most common 
failures and their fixes.  If anyone has any other repeair info, especially
with the last problem, please post it to the net.


	Symptom				Possible Fix
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
No HV or filament voltage	check/replace F401 2A picofuse
				(usually caused by some other failure)

No video or only vertical	check/replace C441 10uF, 35V bi-polar 
line down center of screen
(no horizontal deflection)

No video, middle of screen 	check/replace C439 100uF, 25V
compressed or warped along 
vertical line or screen too
wide.	

No video			check/replace CR408 1N5408
R478 hot or smoking

Low HV or Jittering video	check/replace flyback transformer

Error '2' (NVR) at power	replace E24 (logic board) ER 1400
up or when Setup is saved  	

Bright raster along left 	??????????????????????????????????????
side of screen	

-----------------------------------------------------------------------------
Chad D. Hubich
Technician				hubich@cs.uregina.ca
University of Regina			chubich@ureginav.BITNET
Department of Computer Science
----------------------------------------------------------------------------- 

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Message-ID: <3D222839.7AC34E8E@yahoo.com>
Organization: Road Runner
Date: Tue, 02 Jul 2002 22:25:32 GMT
From: Sark <ian_primus@yahoo.com>
Subject: VT100 help

Thank you all for your help on my VT220 and the null modem cable wiring,
and while I still haven't had time to take another shot at wiring a null
modem cable, I do have the VT220 up and running on the Linux box and the
backspace works. I hope I'm not asking too many questinons, but I
recently accquired an original DEC VT100 terminal. It works, but there
are a couple of annoying little problems...

1). The screen is rather distorted. Characters appear taller at the top
of the screen than they do at the bottom, and the display does not
extend all the way to the bottom of the tube. (stops about 1.5 inches
away from where I think it should) My guess would be that it is a
capacitor failing in there somewhere, but which one? I haven't gotten
inside it yet (see next question)

2). I can't figure out how to get it apart! There don't appear to be any
screws on the bottom, just these funny white plastic things.

3). The "Enter"  key sticks. Sometimes I have to hit it several times
before it will register. I assume this could be fixed by taking the key
off and cleaning the contacts, but I haven't gotten around to it.

4). The "Setup" key is missing (or at least, I assume that is what it is
supposed to say). I figured out how to get into the setup from Richard
Shuford's site, and as there was reference to a "Setup" key, I figured
that it must be the missing one... (in retrospect, I could  have just
pressed it to see what happened, but I thought it was a funtion key or
something, and ignored it) Anyone know where I can get another key?
Actually, any VT100 parts/terminals would be helpful, as I want to be
able to keep a working VT100 around at all times, I just love using it)

5). The terminal's casing is REALLY yellowed. I want to clean it up, but
I don't want to damage the plastic. Any suggestions?

Also, not a problem, but a misconception I had, My VT100's screen is
green. I was led to believe that the VT100's had black and white
screens. This could have been because of a black and white photo, but
I'm not sure. Did they make them in different models like they did
VT220's? If so, did they make them in amber as well?

Thanks in advance, any information regarding the VT100 would be much
appreciated. Thanks!

Ian Primus
ian_primus@yahoo.com

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
References: <3D222839.7AC34E8E@yahoo.com>
Message-ID: <3D22B497.3629A13C@carmen.se>
Organization: Carmen Systems AB
Date: Wed, 03 Jul 2002 10:23:51 +0200
From: Christian Brolin <Christian.Brolin@carmen.se>
Subject: Re: VT100 help

Sark wrote:
> 
> 2). I can't figure out how to get it apart! There don't appear to be any
> screws on the bottom, just these funny white plastic things.

Just pull the centre of those plastic nobs out (down 1/3") with a sharp
screwdriver or knife and then you can lift off the case.

> 4). The "Setup" key is missing (or at least, I assume that is what it is
> supposed to say). I figured out how to get into the setup from Richard
> Shuford's site, and as there was reference to a "Setup" key, I figured
> that it must be the missing one... (in retrospect, I could  have just
> pressed it to see what happened, but I thought it was a funtion key or
> something, and ignored it) Anyone know where I can get another key?
> Actually, any VT100 parts/terminals would be helpful, as I want to be
> able to keep a working VT100 around at all times, I just love using it)

I have some parts/terminals around, but I can't figure out how to
configure my modem for hardware attachments. 

> Also, not a problem, but a misconception I had, My VT100's screen is
> green. I was led to believe that the VT100's had black and white
> screens. 

I think the black and white screens were the most common ones.

/Christian

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
NNTP-Posting-Host: 65.94.149.187
NNTP-Posting-Date: Sun, 04 Jan 2004 17:57:47 EST
References: <bsv3cp$n8f$02$1@news.t-online.com>
    <3FF3D5D7.AC1CCDD6@myownboss.com> <bt9a84$qp0$06$1@news.t-online.com>
Message-ID: <3FF89A14.C12066E1@myownboss.com>
Organization: Bell Sympatico
Date: Sun, 04 Jan 2004 17:56:21 -0500
From: stockwiz <Ffreedom@myownboss.com>
Subject: Re: How to reach contacts of a key on Wyse ASCII keyboard

Matthias Czapla wrote:
>
> stockwiz wrote:
> >
> > This is a common problem with the Wyse KB that  uses the Cherry key
> > mechanism.It is best if you can replace the key. If that's not feasible
> > then a temporary solution(sometims it will work for quite a while) is to
> > take the keycap off and push the stem of the key down while at the same
> > time squirt some contact cleaner inside the key assembly.This had work
> > for me in the past.
>
> I'll try that. Have to get some contact cleaner first.
>
> > Now If I encounter the
> > same problem I basically replace the key. Good luck again.
>
> Two problems. How do I remove the key and where can I get a replacement?
>
> Regards
> Matthias

To remove the key, you have to turn the keyboard over and unscrew the
4 screws that hold the back cover of the KB together. After taking the
cover off you will see the backside of the KB assembly. (If you do not
know how to desolder or solder part on a circuit board, have someone do
it for you. It is just a matter of 2 solder joints for each key switch.)

Once you have the 2 solder joints of the key you want to remove turn the
KB over again and pop the keycap of the key off. Then use a thin slot
screwdriver to lift the key off the housing of the KB assembly. (It is
also a good time now to check for cold solder joints on other keys as it
is a problem with the Wyse KB. It may even solve your current problem if
the key you have problem with has a cold solder joint.)

As for key replacement you can either order form Wyse (expensive) or get
a similar replacement from your local electronic store (if they stock
them). I got mine (a good supply) from a local electronic store a few
year back at $1 each. But I can no longer find it anymore locally.If you
have problem locating the key LMK I could sell you a few for the same
price I paid for it+postage.

 ..............................................................................

Newsgroups: comp.terminals
References: <bsv3cp$n8f$02$1@news.t-online.com>
    <3FF3D5D7.AC1CCDD6@myownboss.com> <bt9a84$qp0$06$1@news.t-online.com>
    <3FF89A14.C12066E1@myownboss.com>
Message-ID: <bth0v5$4ff$02$1@news.t-online.com>
Date: Wed, 7 Jan 2004 14:18:29 +0100
From: Matthias Czapla <derlalert@netscape.net>
Subject: Re: How to reach contacts of a key on Wyse ASCII keyboard

stockwiz wrote:
>
> To remove the key you have to turn the KB over and unscrew the  4 screws that
> hold the back cover of the KB together. After taking the cover off....
> It is also a good time now to check for cold solder joints on other
> keys as it is a problem with the Wyse KB. It may even solve your current
> problem if the key you have problem with has a cold solder joint.

I checked it and the solder joints look perfectly good to me (although I'm
no expert in this area).

> As for key replacement you can either order form Wyse (expensive) or get a
> similar replacement from your local electronic store (if they stock them).
> I got mine (a good supply) from a local electronic store a few year back at 
> $1 each. But I can no longer find it anymore locally.If you have problem
> locating the key LMK I could sell you a few for the same price I paid for
> it+postage.

I really appreciate your offer, thanks. I searched the two German online
electronic stores I know but couldnt find these keys. So I asked Cherry
for a supplier and they will send me some for free! Very nice I think :)
Thank you very much for your help, stockwiz.

Best Regards
Matthias

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
Path: utkcs2!darwin.sura.net!mips!think.com!ames!agate!stanford.edu!rutgers
      !att!cbfsb!cbnewsb.cb.att.com!wa2ise
Message-ID: <1992May10.222121.20507@cbfsb.cb.att.com>
Organization: AT&T Bell Labs
References: <1992May6.170201.12039@phillip.edu.au>
Date: 10 May 1992 22:21:21 GMT
From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Subject: Re: VT220 questions

In article <1992May6.170201.12039@phillip.edu.au>,
 t9114145@phillip.edu.au writes:
>
>I've just acquired a VT220, made in 1985. 'setup' says V2.00.
> 
>How do I connect a printer to it, i.e. what are the pinouts to make a 
>DEC-to-25 pin serial adaptor. Also does anyone have a standard set of
>pinouts for a 25-pin serial printer's 25-pin D?
 
I'd like to know this, too (can't RTFM 'cause I don't have a manual!)
 
>The screen is very jittery right after it gets turned on, but smooths
>out once it's warmer until you can't see the jitter any more. Anyone
>have any suggestions what this might mean or how it could be fixed? The
>20-odd VT220's at college don't do this.

My VT220 had jitter.  Found, in my case, it was a dirty horizontal hold
trim pot.  To get to it, you have to take the back off.  It's on the left
side if the flat circuit board, foward (if memory serves right).  I replaced
it in mine (a 5K trimpot, think I got the replacement from Radio Shark).

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.terminals
Path: utkcs2!gatech!ncar!virga.rap.ucar.edu!ren
Message-ID: <1992Jun5.142628.1101@ncar.ucar.edu>
Keywords: Sources for replacement terminal parts
Sender: news@ncar.ucar.edu (USENET Maintenance)
Reply-To: ren@virga.rap.ucar.edu (Ren Tescher)
Organization: Research Applications Program/NCAR, Boulder, CO
Distribution: usa
Date: Fri, 5 Jun 1992 14:26:28 GMT
From: ren@virga.rap.ucar.edu (Ren Tescher)
Subject: SUMMARY: VT-320 flyback source needed

I wrote:
>
>Yesterday my VT-320 smoked.  Opening the case I found a cracked and
>melted flyback transformer.  I haven't checked to see if it took the
>Horizontal Output Transistor (H.O.T.) with it.  Nor have I called 
>DEC for a part number/price.  No part # is on the flyback.  I have
>replaced flybacks many times before (let me tell you about my RCA
>television repair days!).  Has anyone replaced the flyback before,
>and where did you get it?  The Dalbani catalog did not have a DEC
>category.

From: Blair Groves <blair.groves@canrem.com>
|Ren, you might try calling Sharon Industries in San Jose, California;
|they are at (408)-456-1600... they have a lot of parts for TeleVideo
|terminals mainly, and all the other popular terminal brands. They are
|pretty reasonable about prices. Terry Torres can look after you there.

From: ssi!cjr@uunet.UU.NET (Cris J. Rhea)

    Try Computer Component Source, Inc. (1-800-356-1227)
    A VT320 Flyback is 17.99 qty 1.
    [note: They were the only ones whose catalog I've received so far, and
    they also have a Wyse-60 flyback kit for $11.99! ren]

From: George Konstantinopoulos <george@bert.eecs.uic.edu>
Try CRC Components Inc.  (800)822-1272  or  (714)468-9711

DEC wants a $160 to replace the motherboard! (They won't sell the part).

Thanks to those who replied!
ren n0pvi
dona nobis pacem

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.sys.dec, comp.os.vms, comp.terminals, alt.sys.pdp11
NNTP-Posting-Host: 174.44.24.192
NNTP-Posting-Date: Wed, 03 Mar 2010 18:52:03 -0600
References: <8699c9e7-8396-42eb-a7e3-54734dcfc98f@q21g2000yqm.googlegroups.com>
Message-ID: <y4qdnYKMysKumRLWnZ2dnUVZ_gednZ2d@bresnan.com>
Date: Wed, 03 Mar 2010 17:52:02 -0700
From: GreyCloud <mist@cumulus.com>
Subject: Re: VT420 Flyback Transformer Needed

urbancamo <mark*wickensonline.co.uk> wrote:
>
> Hi folks,
>
> Well, my VT420 let out some magic smoke the other day, and is no
> longer happy. Upon visual inspection I would say the flyback
> transformer is no longer alive. I don't suppose anyone has one kicking
> around in their collection of parts they could let me have (or
> alternatively the board in which it sits)? Would be a shame to have to
> skip the whole terminal.
>
> Many thanks, Mark.


Unfortunately, you'll need more than the flyback to fix it.
You'll need a schematic to identify the parts near it as well.

The capacitors and a diode usually go first and are the cause of
the flyback failure.


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals, comp.sys.dec
Message-ID: <pan.2003.09.08.16.31.17.148795@celigne.co.uk>
References: <bjhl30$vpc$1@online.de>
Organization: VT100.net
Date: Mon, 08 Sep 2003 17:31:18 +0100
From: Paul Williams <news@celigne.co.uk>
Subject: Re: the joy of terminals, part 1: the VT 102

On Mon, 08 Sep 2003 10:19:12 +0000, Phillip Helbig wrote:
>
> I just fired up a VT 102 I have had for a few years but have never had
> in use....
>
> I always am wondering for each piece of hardware---especially terminals
> and monitors---how much idle time is necessary before switching it off
> is the better option, i.e. the gain by not having it switched on is more
> than the loss caused by the stress of switching it off and on.  Any idea
> what that time would be for the VT 102?
>
> I notice that the size of the text decreases from the top of the screen 
> to the bottom.  Is there any way to adjust this, or is it just a
> symptom of age?

Vertical linearity is controlled by R342 on the Video Monitor Board.

VT101 Series Pocket Service Guide: http://vt100.net/docs/vt101-ps/
Be careful when prodding around near the CRT anode!

- Paul

 ..............................................................................

Newsgroups: comp.terminals, comp.sys.dec
Message-ID: <7w77b.233$wu1.211@bignews4.bellsouth.net>
References: <bjhl30$vpc$1@online.de>
Date: Mon, 8 Sep 2003 18:37:16 -0400
From: Homer Simpson <hsimpson@burnsenergy.com>
Subject: Re: the joy of terminals, part 1: the VT 102

The VT320 was notorious for losing brightness over time.  There is an
internal adjustment, but that only gets you another few months of acceptable
brightness.  Replacing the CRT/Bezel assembly is the only fix (or swap it
with another one).

As I recall, there are also adjustments on the 102 and the 320 for both
vertical and horizontal linearity.  You may need a "swizzle stick" from a TV
repair store (or Radio Shack) to do the horizontal adjustments (caution -
don't use a metal allen wrench or you will get burnt!).

To leave on or not to leave on - that is the question.  It kind of depends
on the frequency of use.

 ..............................................................................

Newsgroups: comp.terminals
Message-ID: <bjj36k072d@enews3.newsguy.com>
References: <bjhl30$vpc$1@online.de>
    <tBZ6b.207319$2k4.2349778@news.chello.at>
Organization: Aracnet
Date: 8 Sep 2003 23:26:12 GMT
From: healyzh@aracnet.com
Subject: Re: the joy of terminals, part 1: the VT 102

Jacek Ruzyczka <uv_centcom@yahoo.com> wrote:
>
> I have a similar problem with my VT420 (manufactured in June 1991): 
> Horizontal lines often look "hanging" near the right edge of the screen, so 
> they ain't straight lines any more. Additionally, the characters on the 
> screen sometimes start pivoting a little bit --- just as is if the screen 
> were drunk! :-X

> I suppose this is a matter of age. Besides, it could be electromagnetic 
> interference as I have a 17" PC screen just half a meter away from my VT.

I'm kind of doubtful that the VT420 is receiving interference that is
causing the problem.  What I would worry about is what the VT420 might be
doing to your 17" Monitor.  Based on how the VT420 that's the console for a
couple of my systems messes up the 21" Monitor that's *very* close to it,
when I have the VT420 turned on, I tend to suspect that the VT420 lacks any
kind of Magnetic shielding.

I've seen what unshielded speakers can do to a computer monitor, and it
isn't pretty.  I'd thought they were shielded :^(

                Zane

 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.sys.dec, comp.terminals
NNTP-Posting-Host: c-24-3-109-191.hsd1.pa.comcast.net
NNTP-Posting-Date: Sun, 4 Apr 2010 12:59:50 +0000 (UTC)
References: <3bdfdf0e-d11a-419b-8256-f0bab22adf87@k19g2000yqn.googlegroups.com>
Message-ID: <2be229e2-e677-4eb3-96f4-b8ac2a6027dc@5g2000yqj.googlegroups.com>
Organization: http://groups.google.com
Date: Sun, 4 Apr 2010 05:59:50 -0700 (PDT)
From: jjh <jjhudak@gmail.com>
Subject: Re: VT320 Display Vertical Linearity Problem

On Apr 3, 11:15 pm, urbancamo <m...@wickensonline.co.uk> wrote:
>
> Hi,
>
> I've got a VT320 who's display is not linear vertically. The display
> is half the size of normal and character size shrinks rapidly at the
> bottom of the display to a bright bar. I've tried adjusting the
> vertical linearity and size potentiometers but cannot get a good
> display.
>
> I'm reading general monitor service guides, but was wondering if
> anyone had come across this issue before and therefore might have a
> better idea of which components to look at first. I don't suppose
> there is a schematic for VT320s kicking about anywhere (I've had no
> luck with google).
>
> Thanks for the help, Mark


I would check the power supply voltages, especially in the vertical
section.  If I understand your description, it sounds like there is
not enough vertical deflection on the CRT, which suggests a power
supply.  If the voltages are within 5% for the stated value on the
test points, you will need to scope the linear defection ckt.  I'd
start at the CRT and work backwards.

Given the age of the unit, a capacitor is the most likely faulty
component, but regulator transistors are also a good bet.
Good luck

John


 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Newsgroups: comp.sys.dec, comp.terminals
NNTP-Posting-Host: cpc1-harb7-0-0-cust763.perr.cable.virginmedia.com [92.232.150.252]
NNTP-Posting-Date: Sun, 04 Apr 2010 07:08:15 UTC
References: <3bdfdf0e-d11a-419b-8256-f0bab22adf87@k19g2000yqn.googlegroups.com>
Message-ID: <ggol87-8ma.ln1@neptune.markhobley.yi.org>
Organization: virginmedia.com
Date: Sun, 4 Apr 2010 07:34:24 +0100
From: Mark Hobley <markhobley@hotpop.donottypethisbit.com>
Subject: Re: VT320 Display Vertical Linearity Problem


urbancamo <mark@wickensonline.co.uk> wrote:
>
> I'm reading general monitor service guides, but was wondering if
> anyone had come across this issue before and therefore might have a
> better idea of which components to look at first.

It's probably a capacitor. Drop a silly scope on the various oscillator
outputs and check the frequencies and output voltages to those in your
service guide.

(There might be variation, but have a look--if the outputs look normal,
are they regular? does the output level and waveform look something like
your guide tells you?)

If these seem OK, then you probably need the service manual for the
particular monitor.


If not, what you can do is from the manual determine which oscillator is
causing the problem.

If nothing appears to be at fault, then the problem might be in the high
tension drivers. I hate working with those, so I would probably just dump
the monitor if this is the case. You could discharge the capacitors and
continue to diagnose, if you wanted to though :P

A visual check is a good place to start. Do the capacitors look ok?

Mark.

-- 
Mark Hobley
Linux User: #370818  http://markhobley.yi.org/


 //////////////////////////////////////////////////////////////////////////////

Date: 20 Apr 2002 23:32:57 -0400
Organization: University of Pennsylvania
Newsgroups: sci.electronics.repair, comp.terminals
Message-ID: <6wlmbh4tg6.fsf@saul.cis.upenn.edu>
References: <3CC22D19.F5B94970@yahoo.com>
From: Sam Goldwasser <sam@saul.cis.upenn.edu>
Subject: Re: Televideo 950 problems

Sark <ian_primus@yahoo.com> writes:
>
> I recently accquired an old Televideo 950 terminal. It was rather dirty,
> but it seemed to work (I turned it on for a minute, and it worked fine).
> I got it home, cleaned it up and plugged it in. It turned on fine, but
> then it started to make a high pitched whine, and there was nothing on
> the screen. Then the whine went away and the picture showed up. It was
> stable for a few seconds, then it started to get out of whack and the
> whine appeared again. It was odd looking, it was as if all the
> horizontal lines that made up the image were sliding around left and
> right, and not lining up. The whine increased and the picture got worse,
> then the picture disappeared again and the whine was in full force. The
> picture then came back and the whine went away, and I shut off the
> terminal to prevent doing more damage to it. My best guess would be a
> failing capacitor in the horizontal drive circuit, but I don't know
> these terminals or monitors that well. I have done some simple repairs
> on this sort of thing, resoldering flakey connections and replacing
> blown caps, and I understand the voltages involved. What capacitor/part
> could be causing this? Is this a common problem? I really want to get
> this thing going again, it has such a nice retro look to it :).


This is a real long shot since my Televideo knowledge is packed away
along with fresh dinosaur eggs, but there was a non-polarized
electrolytic  capacitor in the Horizontal-deflection circuit that 
went bad in those things.  However, I don't recall if it would have
had anything to do with your symptoms. ;)

In any case, if you have an ESR meter, check all the electrolytics!


--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/ 
 Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ 
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm 
        | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

 //////////////////////////////////////////////////////////////////////////////

Date: Sun, 21 Apr 2002 01:19:08 -0400
Organization: WWW.US.INTER.NET
Newsgroups: sci.electronics.repair, comp.terminals
Message-ID: <a9tht4$2sse$1@news.ca.inter.net>
References: <3CC22D19.F5B94970@yahoo.com>
From: Jerry G. <jerryg50@hotmail.com>
Subject: Re: Televideo 950 problems

Check the non-polarized caps in the horizontal-deflection output section.

This goes too far back for me!   Also the caps in the scan circuits, and
especially in the power supply can be troublesome in these.

If you replace the non polar caps in the scan section, you require the
proper rated ones.   Don't throw just anything in to the monitor.

-- 
Greetings,

Jerry Greenberg        GLG Technologies GLG
======================================================
WebPage           http://www.zoom-one.com
Electronics       http://www.zoom-one.com/electron.htm
Instruments       http://www.zoom-one.com/glgtech.htm
======================================================

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: sci.electronics.repair, comp.terminals
References: <3CC22D19.F5B94970@yahoo.com>
Message-ID: <ucb16utcbr8l0e@corp.supernews.com>
Date: Tue, 23 Apr 2002 10:58:53 -0500
From: applianceguy <dvdhq@NOSPAM.appliance-world.com>
Subject: Re: Televideo 950 problems

I attempt repairs to TV-955 terminals from time to time.  Most of the
problems I see are in the power supply.  I have a couple that need 
capacitors replaced.  I kinda shotgun them.  I replace most if not all
of the electrolytics, especially the non-polar guys.

I have been putting cheap AT power supplies in these instead of repairing
the factory one.  After removing from the case, they usually fit right in,
maybe with a little bending of heat sinks.  If you're doing a retro-refurb,
a kludge PS might not be kosher, tho...

Paul

 //////////////////////////////////////////////////////////////////////////////
 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\


     Procedures to modify a Televideo terminal for composite video output.


     Materials needed

     1. one bnc connector
     2. one 2N4400 transistor
     3. one 100-ohm resistor
     4. some small gauge wire
     5. solder
     
     NOTE: all these materials are available from a local electronics
           store

     Tools needed

     1. soldering iron
     2. wire cutters/stripers
     3. hand drill
     4. 3/8 inch drill bit


     Modification instructions     


     1. Drill a hole in the plastic connector mounting plate of the logic
          board and mechanically install the bnc connector next the the 
          keyboard cable connector.
          
          ( see diagram 1 )

     2. Locate P2 (plug 2) solder a wire from the outside connection of the
          bnc connector (ground) to pin 3 of p2 on the solder side of the 
          board. Feed the wire through the hole in the board half way between 
          the two points.


     3. Solder the base of the the 2N4400 ( the base is the center lead and 
          is marker b) to the connection for pin 6 of P2. Note: there is no
          pins connected to pin 6 of P2.

     4. Solder the collector of the 2N4400 to the +5 volt etch next to pin 6
          of P2.  The etch also connects to pin 14 of ic # A39.

     5. Solder on side of the 100 ohm resister to the emitter of 2N4400.

     6. Solder a wire from the - lead of C1 on the component side. Connect the 
          wire to the other side of the 100 ohm resister.

     7. Solder a wire from the center connection of the bnc connector to
          emitter of the 2N4400a.

     8. Cut the etch between option E1 and E2. (located next to P2)

     9. Connect E3 and E4


     Diagram 1
     
     ------------------------------------------------------------------------
     |                                                                      |
     |                                                                      |
     |           O           -----       ---------------   --------------   |
     |          O O          |kbd|       | printer     |   |    rs232   |   |
     |           O           -----       ---------------   --------------   |
     |           ^                                                          |
     |           |                                                          |
     |         bnc connector                                                |
     ------------------------------------------------------------------------

 //////////////////////////////////////////////////////////////////////////////
 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

Newsgroups: comp.terminals
References: <3E28B332.F76E0F6@ev1.net>
Message-ID: <3e2a40c0$0$79564$7f8943f3@newsreader.visi.com>
Organization: VISI.com
Date: 19 Jan 2003 06:08:00 GMT
From: Seebs <seebs@plethora.net>
Subject: Re: Wyse-60 Information Sought

In article <3E28B332.F76E0F6@ev1.net>,
Charles Richmond  <richmond@ev1.net> wrote:
>
> A friend has a Wyse-60 terminal, and the keyboard is locked up.
> He can *not* get the keyboard to communicate with the terminal.
> Is there a standard way to reset without using the keyboard???
> How can he fix this???

Well, just for what it's worth, I had this problem with a WY-160, and shaking
the terminal fixed it.  It seems to come and go if the terminal is moved.

-s
-- 
   Copyright 2002, all wrongs reversed.  Peter Seebach / seebs@plethora.net
   $ chmod a+x /bin/laden      Please do not feed or harbor the terrorists.
     C/Unix wizard, Pro-commerce radical, Spam fighter.  Boycott Spamazon!
Consulting, computers, web hosting, and shell access: http://www.plethora.net/

 //////////////////////////////////////////////////////////////////////////////

http://www.wyse.com/service/support/kbase/wits/80521.txt

TITLE: Miswired CRT connector

DATE:  8/6/91

PRODUCT: Wyse  WY85  WY99GT  WY50

THE ISSUE:
       The Monitor Power Supply board I just installed fails.

OVERVIEW:
        Improper marking (silk screen) for position of the
        "Blk" and "Brn" CRT connector wires on the Monitor Power
        Supply PCB.

RESOLUTION:
        Desolder the connector wires from the PCBD. Change positions
        of the Brown, and Black wires...re-label the PCBD properly.

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
NNTP-Posting-Host: 151.38.235.63
NNTP-Posting-Date: Sat, 03 Jan 2004 14:30:14 MET
Message-ID: <GtzJb.227555$e6.8972880@twister2.libero.it>
Organization: [Infostrada]
Date: Sat, 03 Jan 2004 13:30:14 GMT
From: leonardo cerliani <leociri@libero.it>
Subject: Wyse Kb, some keys don't work

hello everyone,

    I recovered in my university a Wyse terminal WY-55ES and a Wyse keyboard
model 901866-05 that were going to be destroyed. They weren't close to each
other where I found them, and that's my first (long wished) serial terminal.
I opened the keyboard to clean the internals, and noticed that some lines on
the three plastic sheets are darkened. I switched on the terminal and the
most of the keys work, but there are some keys (many, and not always
contiguous) that doesn't. As I'm unexperienced, I'd like you to advise me
about what product could I use to clean the lines.

    The main reason why I thought to write you is because I also guessed of
the case that this keyboard could not be appropriate for that terminal.
Could you tell me something about this?

    Thank you very much

    leonardo cerliani

 ..............................................................................

Newsgroups: comp.terminals
NNTP-Posting-Host: 151.37.172.132
NNTP-Posting-Date: Mon, 05 Jan 2004 00:35:15 MET
References: <GtzJb.227555$e6.8972880@twister2.libero.it>
    <bt9anm$qp0$06$3@news.t-online.com>
Message-ID: <Tq1Kb.230876$e6.9128891@twister2.libero.it>
Date: Sun, 04 Jan 2004 23:35:15 GMT
From: leonardo cerliani <leociri@libero.it>
Subject: Re: Wyse Kb, some keys don't work

> There is lots of information about
> what keyboard works with what terminal
> at the Wyse website (www.wyse.com) under
> the support section.

thank you very much, I didn't noticed this page at first

    http://www.wyse.com/products/gpt/msrp.htm

at least, now I know I have a hardware failure...

best regards,
leonardo cerliani

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.sys.sgi.admin
NNTP-Posting-Host: cpc4-cmbg8-5-0-cust114.cmbg.cable.ntl.com
NNTP-Posting-Date: Tue, 25 Jan 2005 09:42:21 GMT
References: <1106410343.908492.80730@f14g2000cwb.googlegroups.com>
Message-ID: <1woJd.145$tF6.29@newsfe6-gui.ntli.net>
Date: Tue, 25 Jan 2005 09:42:21 GMT
From: Tristram Scott <tristram.scott@ntlworld.com>
Subject: Re: SGI Octane power issues

LindseyWetteland@gmail.com wrote:
[snip]
>
> When I first got the Octane (a week or so ago) it powered on and
> functioned fine.  Suddenly it started turning off on its own 
> (it behaved as if someone yanked the power cord - no nice shutdown
> messages in Irix, etc).  Now it rarely turns on.
>
> SOMETIMES, (talking like once in 200 times or so) it will power on,
> but rarely stays on more than four to five minutes.  There does not
> appear to be any rhyme or reason as to why it turns on sometimes for
> a little bit.
>
[snip]

Sounds to me like classic symptoms of worn out electrolytic capacitors in
the power supply.  If you have some spare time, and feel confident working
with a soldering iron, you could try and replace all the electrolytics on
the high voltage board.  They are very cheap, and readily available.

Tony Mantler has instructions for doing this for an Indigo2.

    http://www.apia.dhs.org/i2ps/

The concept should be the same for the Octane.  You will find the Octane
power supply is (slightly) easier to dismantle than that of the Indigo2.

Do remember, though, that there are lethal voltages inside the power
supply, even when it is switched off.  If you don't know what you are
doing, leave it alone and buy another.

-- 
Dr Tristram J. Scott
Energy Consultant

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
NNTP-Posting-Host: c-76-106-151-252.hsd1.fl.comcast.net
NNTP-Posting-Date: Thu, 24 Jul 2008 21:58:51 +0000 (UTC)
References: <d1ad70eb-5737-4c8c-ab55-3c184f88fb9c@d45g2000hsc.googlegroups.com>
Message-ID: <8a029197-dd82-4b32-ad72-b3df2282dbed@u6g2000prc.googlegroups.com>
Date: Thu, 24 Jul 2008 14:58:51 -0700 (PDT)
From: ChucksterInJax <pbear22@comcast.net>
Subject: Re: Looking for schematic for a Zenith Z-29 Terminal

On Jul 16, 7:12 pm, ChucksterInJax <pbea...@comcast.net> wrote:
>
> Last month I won a Zenith Z-29 terminal off of eBay. Received it
> without damage, but, when I powered it up, a puff of smoke came out 
> of the top vent. Looks like a resistor has fried and I can't tell
> what the values were.
>
> I am now looking for a schematic or service manual for the Z-29
> terminal. Does anybody have one or know where I can obtain one?


I believe I found the problem without the schematic. The charred
component was not a resistor, but a solid tantalum capacitor between
the output of a 7805 5V regulator and ground.

The datasheets for the 7805 have a diagram with a 0.33 uF tantalum on
the input and a 0.1 uF on the output. Should be an easy fix.

 //////////////////////////////////////////////////////////////////////////////

