17 Dec
2001
17 Dec
'01
3:06 p.m.
On Dec 18, 0:07, Johnny Billquist wrote:
much
It works, but it requires more work.
It doesn't work very well. It's almost impossible to get all the crud out
Plenty of QBus cards use TTL, basic 74 series, not just LS. I just pulled
a few out to check. In the faulty ones I referred to, it was some TTL
PROMs in one of them that had gone (lost several bits), and I can't
remember what was wrong with the other one. Nevertheless, even original 74
series TTL is static-sensitive, and the worst part is that things can be
degraded by ESD without failing completely. That's why modern circuits
include extra ESD protection.
--
Pete Peter Turnbull
Network Manager
University of York
On Mon, 17 Dec 2001, Pete Turnbull wrote:
> Domestic ones I've seen won't. Apart
from the soaking -- that's the
point
> of using it, obviously. Very few things are
intolerant: some relays,
> transformers, a few types of switches, etc, usually just because they
take
too long to
dry out. And core mats, of course, because they're very
fragile and extremely hard to repair.
Don't forget old transformers, which often use something looking very like paper for isolation.
Agreed. That's why my PDP-8/E's H740 power supply got a different
treatment. It still got washed, though.
Grab a bottle of isopropanol, some swabs, and start
working.
Doesn't work well on smoke-damaged boards, Coke, etc, and water is far
cheaper and safer (for the user, too). from under ICs, DIL switches, or sockets. IPA does not
do a good job on
smoke-damaged boards.
> TTL may be
> much less sensitive than old CMOS and even modern CMOS and TTL
> replacements, but it is still sensitive and can be damaged by ESD.
It's
> not so likely to be damaged when soldered into a
complete circuit, but
it's
possible.
I've had at least two QBus boards damaged by ESD through
careless handling.
Eh? Q-bus cards, even the oldest you can find, are LSI stuff. You won't
find much of anything even *that* modern in a PDP-8. Actually, much Q-bus
stuff is really modern compared to what I'm thinking of...
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