Hi John,
I know that socket problems in the 1970's could be a real
bear, but most of them started very early in the life of
the product. For instance, I had heard about smacking
Apple I memory on the table to fix problems by the time
they had been out for only a couple of years.
Maybe my 5370A already has replacement sockets? I'd have
to look, but since it is working reliably, I am not feeling
really inclined to de-rack it to check.
I have used gold plated machined-pin sockets for many years,
and never saw a failure due to the gold/solder interface.
I am certain that to some degree the problem is real, but
it is also not real most of the time. Stressed joints are
certain to be a contributing factor.
If you look carefully at the augat machine-tool sockets, you
will likely notice that there is a tunnel that runs under the
socket so that you can strap the IC into the socket. A good
idea much of the time. I have never had a plastic packaged
IC fall out under any circumstances, but I can see where the
more massive ceramic packages (eg. 5400 TTL) might be a real
problem.
It always bothered me a little bit how the fingers in a machined
pin socket are not in any way aligned with the faces of the IC
pin. They are clearly designed for a round pin! ... and are
being used on a square pin with random orientation. Probably
not an ideal situation.
When I bought my 5370A, I also bought an 8082A so that I could
service it. The 8082A is about the only generator that is up
to the task.
It was a major disappointment when the 5370A turned out to be
working well, and in specification. Hopefully it will drift
out so I can put in the differential linearity modification,
and calibrate the beast... in the mean time I will just use
it.
-Chuck Harris
John Miles wrote:
As to the socket issue, my 5370A has been dead reliable. No problems at
anytime.
I think your socket issue is unique to your unit, or perhaps the
series your
unit came from.
I've heard of socket failures happening on at least one 5370A besides
Didier's, but I don't think it's reached pandemic proportions yet. Seems
that the socket manufacturers didn't really understand their own reliability
figures back then. I've been bitten by them myself -- not by my 5370, but
by the Apple II+ I had as a high-school kid, which used similar DIP sockets
on every chip.
My guess is that the gold-plated machined-pin sockets will be fine for the
duration. The pins probably saw enough tinning during soldering, and if
not, you can just reheat them later if needed. So far, I've seen problems
with gold-to-copper solder joints only in cases where the rule against
making a physically-stressed solder connection has been violated. The 8662A
is prone to those problems because HP failed to use pigtails to connect
their SMC center pins to the PC boards. A bigger problem with the
machined-pin DIP sockets is that they can let go of their chips if subjected
to vibration in some orientations, another fun phenomenon that the
manufacturers don't seem to talk about.
5370s are nice boxes but they can be a challenge to work on. There are a
couple of editions of the service manual, both apocryphal at best. One
concern is that the interpolators are hard to calibrate properly without an
8082A pulse generator (read: I'm not sure how you'd even attempt it.)
-- john, KE5FX
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