Hi Group,
This is my first post with this group, so be kind!
I have a busted oscilloscope. This one is a factory modified Phillips/Fluke PM3050. The scope was running in a warm environment 5-10 years
24/7, and it sure seems that every electrolytic with the Phillip logo is open circuit, and weightless! These capacitors lost their juice! One shorted and exploded. Anyway after replacing three shorted diodes, a power fet, blown trace, burned AC line Molex connector, and 6 capacitors I got it powered up, and with a trace. Not bad, but the power supply is making audible noise (maybe 200hz), efficiency is low (hot fet heatsink), and the trace has modulation from what I presume is power supply ripple. It could be the Anode voltage varying around. I am at the point where troubleshooting without a schematic is getting to be a pain with a lot of guess work. I looked at 3 P/S outputs +12, -12, and +10. These all are clean and stable. I need to replace more capacitors I know, but I was hoping to find a diagram to help me isolate what is going on with the switching off line power converter. There is a HV transistor, and a power fet sharing the same heatsink, and they seem to be in series. The fet and a high speed diode were popped.If any of you fine folk have the power supply schematic, could you scan in a copy for me ? I am mostly interested in the power supply PCB.
Thanks in advance! Jim Candela WD5JKO