From: Ethan Dicks <ethan.dicks(a)gmail.com>
Subject: Re: VT320 Terminal RS232 Receiver
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk(a)classiccmp.org>
Message-ID: <f4eb766f05012615515fe34742(a)mail.gmail.com>
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On Wed, 26 Jan 2005 10:47:31 -0500, list(a)saracom.com <list(a)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.