Michael A. Terrell wrote:


CMOS is sensitive to spikes on the power rails. It sounds like
someone should make a replacement board with modern ICs. It wouldn't be
that difficult, with a schematic of the original board.


Obviously, Lincoln has this figured out. If operating inside a welder
with 300+ Amps and the HF system going doesn't upset it or cause random
failures, they did their homework correctly.

I also use 4000-series CMOS in servo amps with 120+ V and 20 Amps, because
they can run off 12 V rails, therefore more immune to electrical noise.

Jon