I can't find the thread about the radio/cassette/CD player that worked
for a while after I jiggled the on/off slide switch and then stopped,
and then jiggling wouldn't make the power light even flicker in the
slightest. But that tended to convince me the problem was somewhere
else.

But just before I left, I figured there was nothing to lose so I took
the knob off and sprayed just a little bit of the stuff in the top of
the slide switch. The can was blue and red or something that reminded
me of WD-40 but its name was nothing like that.

Anyhow the radio went on immediately after turning it on, no jiggling
required. So WD-40 looks pretty good for cleaning the contacts on a
power switch, probably carrying 12 volts.