Hi Tom,
I have the same power supply as yours and it's a faulty one also...I wonder if you sojve your problem and if you could identify fhe HP900 component ? I also think that it is an optocoupler, but not sure at all! It's a pity we can't find the exact schematics of this power supply!
My primary circuitry looks fine, have made some tests connecting 12 v from an external power supply so the NE5560 is running, signals seem to be OK on the buck regulator and the DC-DC converter.
So may be the problem is in the feedback??
If you have any infos, I thank you in advance!
73,
Roland F8CHK
