> I've been cleaning up my recently-acquired PDP-8/E, and I've had to

Yes, that's a very common problem... Makes a right mess on a the

I have never seen conductive foam used on PDP8/e machines. There's nothing particularly static-sensitive in there anyway (the CPU is all fairly large-junction bipolar chips (TTL, etc). Mine just had the normal brown foam throughout. Since you can put options with top connectors anywhere in the backplane, there would seem to be little point in having special foam over the front slots only. But the leakage on conducive foam is not that high, and I doubt that using it would cause many problems (TTL inputs are fairly low impedance). It might have an effect if used over core memory units, but actually I doubt it.