My 8643 failure message indicated 5V supply failure. Voltage at test
point measured 4.9 volts. I replaced all the capacitors in both
switching supplies of the 8643A. Both supplies checked out OK before
capacitor changes, and OK after capacitor changes. But I'm happy it has
new capacitors.

The battery voltage was OK, but being old and not interested in leaks,
it has a new set of 3xAAA in little plastic holder.

After reading about tinned Molex connectors developing voltage drops I
sprayed DeOxit on pins of the power supply connector, and both input and
output connectors of the power filter board. And of course the cable
pins that plugged into those connectors. Power supply and filter board
input connectors were tinned pins. Pins on the output end of the filter
board were gold. Did the best I could, but it wasn't as good a job as I
would like to have done.

NONE of the connector bodies were discolored. There was maybe 1/4 volt
drop, and not that many hours of use, before I took it apart. Probably
not enough time and heat to discolor the Nylon.

Applied power, and test point now measures 5.10 volts. So looks like it
was voltage drop in the tinned Molex connectors.? No error message.
While I haven't checked exhaustively to verify everything is working,
but I expect it's OK again.

THANK YOU GUYS FOR POINTING TO THE CONNECTORS

Regards - Bill W7AAZ