SB-104A Counter Circuit Board

[BMW]

I agree. I still work at what's left of the "real" HP (Agilent) and we never
used sockets, as Dave said, except for EPROMs and these days sometimes
FPGAs. The sockets we did use for through-hole parts had machined, gold pins
that really grabbed the ICs. Of course, back in those days, we also had
gold-plated circuit boards, not the SMOBC (Solder Mask Over Bare Copper)
that we use today, and that made it much easier to remove parts without
lifting traces. Ah, progress!

Contrary to popular belief, ICs can and do "wear out" over time. There's a
thing called ion migration that can slowly make them inoperable. Heat and
overstressed output transistors can also take their toll. It's a decades
long process, but it does make you wonder how well the electronics of today
will fare 50 years from now, compared to the tube rigs that we can still use
with relative ease today.

73,

Brian, W0DZ
www.dzkit.com


-----Original Message-----
From: Heathkit Owners and Collectors List
[mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of David Ritchie
Sent: Friday, October 07, 2005 4:59 AM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: [HEATH-TEMPE] SB-104A Counter Circuit Board


JF writes:
>The sockets on my SB-104A counter board caused so much trouble that I
>finally removed all of them and soldered the ICs directly to the board.
>Fixed the problem, but not having sockets makes it harder to do
>troubleshooting if an IC goes bad later. You might consider buying some
>high-quality sockets and replacing all of the originals. Try to find
>some with gold-plated contacts that are closed at the bottom and will
>not allow solder and flux to wick into the contact areas.

  As you mention later, sockets are a cause of a lot of problems. When I
worked at HP, they almost never placed sockets on boards as they were
evidently a major source of failures. Read as: "Sockets are evil!"

  I would recommend against using sockets. I have found that the problems
with them over time outweigh any advantages for production boards. The only
place I would even recommend them is with EPROMs, and I would then
lean towards the high quality sockets as discussed earlier. If is something
that was going to see a lot of vibration, I would not use them
at all.


  Instead, solder the IC directly to the board, and when/if it fails, cut
the IC out from the chip side of the board and then use an appropriate
wattage soldering iron, solder sucker and pliers to remove the old solder
and pins. Be careful here not to use too much heat, due to the
age of the boards and the risk of delamination of traces from the PCB.
Then replace the IC with another of the same type.

73, Dave N4DJS

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