Thanks again Brian,
- Checked C2008, C2002 capacitance (<±5%) and leakage (<1µA @30V), seem ok.
- R2010 within 1%.
- D2010 seem ok, Vf ~ 3.1V. D2011 not mounted.
- HV cap at the tube look good, the connector have no oxide or dark spots. Cleaned with IP and reseated. Thanks for the hair-dryer tip!
- Cleaned tube connector PCB with IP. It was not particularly dirty.
- No flashes visible. Checked along the high tension cord, the PCB/connector, the cap and inside the tube in a pitch black room.
- Found two possible cold soldered capacitors that was fixed, C331 and C332 (schema page 2, top right corner).
Observations (probes 10X, grounded in chassis);
+140V stable, no 100Hz ripple and about 5% ripple from the sparks (or whatever it is):
+5V shows about %20 ripple from sparks.
+12V have significant 100Hz ripple, and massive transients from the sparks:
+16V (unfiltered rail) looks similar to +12V.
I then checked PSU capacitors C1001, C1002 and C1010 for ESR (<1Ω) and capacitance (<±5%). Ripple could be due to high current draw i suppose. But can regulation be a factor? It does regulate though, it's pretty close to 12V and -12V on the rails.
A question; would there be any harm to disconnect +16V to the HV charge pump, i.e. P1003/CN2001? That would mean that everything is powered except the anode voltage if i read the schematic correctly. I'm curious if that would bring down the ripple on 12V to a sensible level, and hopefully isolate the problem to the anode voltage, if that is the culprit.
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Correction: +5V has a horrible spikes from the sparks as well. Sorry!
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Here's the +140V rail, which in fact is 160V.
The schematic seem to mix 140V and 160V, not sure what is going on there.