My Tek model 570 vacuum tube curve tracer seems to have
lost the ability to keep the high voltage running. When
it is first powered on, I get a nice trace, but the HV
oscillator tube (6AQ5) looks like it's really unhappy
about it. In a minute or so, the high voltage goes
away with the usual dim expanding trace.
I've replaced the tubes, and don't see anywhere the
supply is overloaded, so I'm guessing a failed
capacitor or shorted turn in the transformer.
If this unit uses those little oil-filled caps in the HV supply,
try hitting them with some freeze spray. My RM545B did this
(as well as smoking the 6AU5 cathode resistor) due to electrical
leakage in the .001 uF 1KV oscillator tank cap. Chilling this
cap made the problem go away temporarily. I replaced it with
a ceramic disc with the same value and rating.
PS- looking for a 577