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mole42uk · 5th Aug 2018, 3:17 pm

Back to it, I couldn't leave it alone. The front panel indicates it's doing a ROM-TEST, then AUTO-SETUP but sticks there. No display, but the AC heater voltage is present and correct.

Further checking revealed no 260V supply, the 1µF tantalum that I thought exploded was actually okay, it was the 150R resistor next to it. Replacing that revealed a high current demand on the 260V rail, which is connected to the pre-amp board at PLNV14. From there is a mess of surface mount components, so that's an investigation for another day.

On the positive side, I did test the other pre-regulator daughter board which works okay.

5th Aug 2018, 3:17 pm	#29
mole42uk Nonode Join Date: Aug 2010 Location: Resolven, Wales; and Bristol, England Posts: 2,612	Re: Gould 4072 bad PSU Back to it, I couldn't leave it alone. The front panel indicates it's doing a ROM-TEST, then AUTO-SETUP but sticks there. No display, but the AC heater voltage is present and correct. Further checking revealed no 260V supply, the 1µF tantalum that I thought exploded was actually okay, it was the 150R resistor next to it. Replacing that revealed a high current demand on the 260V rail, which is connected to the pre-amp board at PLNV14. From there is a mess of surface mount components, so that's an investigation for another day. On the positive side, I did test the other pre-regulator daughter board which works okay. __________________ Richard Index: recursive loop: see recursive loop