[Boatanchors] CMOS Failure

[Ulrich N Fierz]

G'day Paulassume you're talking about DIL chips in plastic cases like the early 4000 series. Failures in 70ies/80ies ICs due to other reasons than I/O stress occur due to various reasons. One of the more common causes is internal corrosion due to humidtiy leaking in along the pin legs. Have experienced this problem on various communication gear and described in general on my website. You might want to have a look at this:
hb9aik.ch/notes/plasticpack.htm


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1970ies Plastic ICs

Ulrich Fierz

Plastic ICs
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Ths solution to this is obviously replacing the chip - but with a later manufacturing date. The usual 4000 series is mostly still available.
Hope this puts some light on the issue.
Good luck and have fun with your restorations,Ulrich
Ulrich Fierz8044 Zurich/Switzerland