So the computer literally did not operate because of
a burned out light bulb. When I replaced the bulb,
it worked just fine.
TO go completely off-topic, I have an old Heathkit PSU where the supply
to the zener diode reference is itself stabilised by a gas discahrge
tube (somethling like an OA2). And the series resistor for that tube is
the (110V) power-on lamp. And yes, I was given it becuase it didn't work,
and the reason it didn't work was that the lamp had failed.
-tony