30 Apr
2021
30 Apr
'21
11:55 a.m.
Brad Spencer <brad(a)anduin.eldar.org> writes:
Thanks for your advice, Brad!
The University was running a current loop set up with
very long runs
all over campus and lightening would tend to take out a serial
terminal from time to time.
That would do it. In my case, it's carelessness with connections
between different in-house power circuits. I live in an older house,
with three phases in, and pairs of them used for the individual 240v
circuits, of which I have two in my hobby room. Imbalances (caused by
exterior faults) can cause ugly spikes when connecting or disconnecting;
I've become very careful about making sure all computer equipment in the
room is on the same circuit, with good ground connections.
...which reminds me: I once worked for a company whose offices stretched
throughout the same floor in two adjacent city buildings. Never really
gave that fact a second thought, until I grabbed a grounded metal RS232
connector with one hand, rested the other on the grounded metal chassis
of the machine it was connected to, and pulled the connector. The other
end of the cable was grounded in the other building. I needed a short
break after that before continuing work...
You did not mention the age of these terminals, but I
would also
suspect caps going bad somewhere.
Mm. Old caps do that. I recently had one blow in a DEC BA23 power
supply, which I pulled, and replaced with a spare one I had on hand.
That lasted all of five minutes before the same capacitor blew in the
replacement. Turns out they have noise suppression caps on the line
input, and these go bad and explode. Doesn't affect anything else,
though, so I just swapped in new ones, and the supplies work fine.
-tih
--
Most people who graduate with CS degrees don't understand the significance
of Lisp. Lisp is the most important idea in computer science. --Alan Kay