[time-nuts] HP 5370B vs SR620

[John Miles]

> 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