"Eeyore" wrote in
message

NEVER put capacitors across switches without a serious
watty R of about 100 ohms in series too.

Agreed.

I've seen the results. DRAMATIC barely explains it.

Not only that, but without the R you might be creating a high-Q resonant
circuit that actually makes the arcing of the switch appreciably worse.

Ever seen a capacitor literally EXPLODE and shower the
internals with metallised foil ?

No scare stories needed - a carefully-chosen series resistor generally makes
the bypass in *more* effective at reducing EMI when the switch is operated.
I daresay that the possible high currents with a high-A circuit sets the
stage for the capacitor failure in some cases.