VT-131 prints?

[Allison]

>
>Subject: Re: VT-131 prints?
>   From: Ethan Dicks <ethan.dicks at gmail.com>
>   Date: Sat, 02 Jul 2005 15:25:41 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 7/2/05, Allison <ajp166 at bellatlantic.net> wrote:
>> Common VT1xx part failure.  Seemed they made the video board with a
>> 50V cap where a 100V cap should be.  Huge numbers of them were made
>> and failed but amazingly there are still many in use that havent.. Yet.
>> It is repairable as it cooks a cap, diode and resistor.
>
>That sounds like once someone traces down the problem, it belongs in a
>FAQ somewhere.
>
>I haven't had any failures like that, so I guess I'd like to know
>more, especially to buy a bag of 100V caps and preemptively fix some
>of my terminals (I have stuff ranging from gen-u-ine VT100s, to 
>VT102s, a VT103, a VT105, a DECmate I, etc., and I don't recall if I
>have a VT125 or VT131 or not.
>
>-ethan

All qualify.  It's the board in the monitor (display) that is in 
question.  There is a (memory test) 100mf 50V cap and it's subject
to more than that (about 70V).  It was fixed in production and 
who knows how many field repairs by board replacement, I once saw
a crate of dead boards 4x4x6ft full, and that was a sample.  If 
the cap is replaced with suitable the failure is unlikely.  I 
have several VT1xx and all have been fixed over 10 years ago.

Failing boards display height and linearity problems before they fry.


Allison