cctech Digest, Vol 17, Issue 28

[Max]

>From: Ethan Dicks <ethan.dicks at gmail.com>
>Subject: Re: VT320 Terminal RS232 Receiver
>To: "General Discussion: On-Topic and Off-Topic Posts"
>         <cctalk at classiccmp.org>
>Message-ID: <f4eb766f05012615515fe34742 at mail.gmail.com>
>Content-Type: text/plain; charset=US-ASCII
>
>On Wed, 26 Jan 2005 10:47:31 -0500, list at saracom.com <list at saracom.com> wrote:
> >
> > Hello,
> >
> > I managed to feed -48VDC into the data receive pin of my
> > VT320 at work.  So of course the magic smoke came out.
>
>Ow!

Yea, did not make my day.  We do telecom testings.  Most everything
is -48VDC battery powered.  So I managed to accident get the battery
power across the equipment's frame ground and it then put the voltage
on the receive pins and lord knows what else.

> > Which chip is the receiver chip?
>
>If the VT320 is like its predecessors (VT220...), it uses 9636 and
>9637 chips, *not* 1488s and 1489s.  I do not recall off the top of my
>head which one is Tx and which one is Rx, but if you get the pinouts
>for the chips, it should only take a couple of minutes to determine
>which is which by using a continuity tester/VOM to trace out the input
>pin from the interface jack.  Both the 9636 and 9637 are 8 pin DIPs,
>so it wouldn't even take that long *without* a chip pinout.  You just
>need to know which is the RxD input from the outside world... the chip
>that's attached to that would be the fried one.
>
>Also... you might be able to spot a pinhole or other mechanical damage...


I found the two drivers chips (9636).  They had a different number but they 
cross-listed to the
9636s. There was another 8 pin chip  between the two and the traces look 
like they might run to it.
So its probably the receiver.  However it has a number different than the 
9637.  I of course
forgot to write it down.  So is life.  Anyway might be a mute point for now 
as I remembered I
have another VT320 in the shed with a bad tube.

Anyway, Digikey lists the 9637 as available so I might try fixing the board 
as a spare.   Thanks
for the help.  Of I will also put sockets in.