and capacitor coupling it instead, if you like. Back when there were long cables on personal computers, and static charge accumulated here and there, then was discharged into earth-ground, as a consequence of periodic movement, as in a printer or the like, this helped with problems like that. Simply cut the signal GND free from chassis gnd, and replace the connection with a 1 microfarad cap of, say, 50 volt working voltage. I've never given this much thought, but it seemed to relieve the trouble.

Another thing that made considerable difference back then, was series resistors, of, say, 4.7 k-ohms on all inputs from switches, pushbuttons, relays, etc. You'll have to pick values appropriate to your specific application, but with CMOS, that was a common value to mitigate such problems.

Now, there's no guarantee that your problem is ESD, is there?

RE