I've got this ship's clock (Wempe Chronometerwerke) to fix. The
PSU had a hissy (literally) fit and has taken out a few components.
Now I have to decide on the extent of the repairs. The ship is on
a world trip and is out of port temporarily until the 30th, when it
returns and then continues its voyage, so whatever I decide has
to be doable in a fortnight

The unit was built in 1977 and I feel I should replace all the ICs,
even those that aren't faulty. Yet. There are 11 180mm x 120mm
cards in a 19" rack, quite a few dozen ICs. The display's 74s are
history because of the PSU's fault 14V output, but the rest are
4000 series that I think will have survived

Has anyone an opinion on the lifetime of CMOS ICs, with regard
to atmospheric ingress or just electronic wear and tear ? This clock
is on 24/7/365, so there's some constant warmth and it shows no
signs at all of salt corrosion. I know that ICs unpowered for a long
time can fail when powered up but I'm not sure of the exact cause

The last job I had like this was of a similar vintage and was flakey,
to say the least. I ended up replacing a very large (450mm x 95mm)
PCB with 60 ICs with a small PIC circuit. I'm tempted to do the
same with this clock, but I'd need to do a cost analysis first and
run that by the customer. Time and the need for them to carry on
with their journey is a factor

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