My ancient Amana Microwave oven numerical display is out. Has been acting up
for years, but I now use it daily. (Batching it. Dear Wifey now in heaven.)

I can punch in the time I want, and the oven will run and turn off
accordingly. But I can't see the countdown any more because the display
digits are out.

Well they really are not out... just that the lower left segment on all four
are lit continuously, not other segments ever avtivate. Once and a while #1
"4" and occasionally #2 "2" light on cue during the countdown. I've opened
it up and measured power supply voltages and they are correct and normal at
the power supply.

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

Any suggestions?

Ange