Thanks, you pretty much crystalised my thoughts precisely. The next step AISI is to eliminate the transformer as the source of the problem, because if that's faulty I may as well junk the whole thing. So that must be my focus first and foremost. I should really have done that much earlier in the process, TBH.
Actually years ago in the TV biz I was thinking of building a circuit that would do just that. Specialized instead of cobbled together. Partly for fly backs and partly for things like this.
I have not completely studied the print for your PS there but I know that 9
9 % of them run above resonance and lower frequency under load. If you exci te it with 15 KHz you might not need all that much amplitude.You will no doubt need a fan on the amp even for short runs. Also note that you can feed just about any winding you feel like. If that thing doubles t he line voltage it is looking for maybe 320 P-P or more. You will not get t hat out of most audio amps. you might want to build one and run the generat or so hard it clips hard and then control the output with a variac. that wa y your transistors are in saturation and not burning up. And then you can k eep the gizmo for future use.
Either way, of course monitor the voltage. Another thing might be to just t ake a sine wave out the generator right to the transformer and determine it s resonant frequency. Alot of generators have a 600 ohm output, that is hig h enough to determine its resonant frequency as the amplitude will be highe r. Now the problem is that we don''t know what the frequency is supposed to be. I would say though that if it is up like 1 MHz it is probably bad.
Or there could be open caps across it somewhere or something shorted or... you got you one hell of a job there. You know, SMPSes could be so easy, a f riggin oscillator, PWM, but NOOOOO (in the voice of John Belushi) they have to do something exotic. Who do they think they are, Tektronix ?
I quite agree. Some of them are absurdly complex and I've often wondered if the designers got paid by the part-count rather like the lawyers of yore got remunerated by the word. This one runs at about 20kHz. I was able to determine that because it will run (badly) for a few seconds before that 20 ohm power resistor starts to burn up. Yes, a beefy audio amp would be ideal but I'm going to just try putting in the waveform from my valve (toob) sig gen directly to the primary to begin with (it's 600 ohm like you say) and if that fails the second intermediate step of an audio output transformer if I can find a suitable one. If the HT windings are truly shot to bits, then their breakdown may well be visible as twitching secondary waveforms at much less than the intended operational voltage level.
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