28 Jan
2005
28 Jan
'05
1:04 p.m.
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>
Content-Type: text/plain; charset=US-ASCII
On Wed, 26 Jan 2005 10:47:31 -0500, list(a)saracom.com <list(a)saracom.com> wrote:
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.
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! 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...