german-pinball Double check your pic there. The upper point must be moved down one trace, you have the 4v line grounded.

No problem, I just happened to be studying my own power supply at length tonight trying to debug it.

I recently tried Krud Kutter original with water maybe 1:10 and magic eraser. It didn't turn white but got probably half way to it. It seemed to raise the grain a bit due to the water but settled back down when dry. It didn't remove paint in that concentration. YMMV

If you don't have an insulating bushing handy but have the mica you could get by temporarily with a nylon screw. Or even a zip tie cinched really tight just to test it out. I wouldn't run it long like that though.

Nope that's the idea of the insulator. The back of the transistor transfers the heat through the mica. If you connect that tab electrically to the aluminum you will short it.

If you still have a radio shack near you they carry them.

https://www.radioshack.com/collections/heat-sinks-standoffs/products/to-220-mounting-hardware

Yeah I think it's a lousy photo, I remember them as a shoulder washer. Either way if it wasn't you could shrink tube the screw.

Did you go through Clay's systematic power on guide? Very helpful:

http://www.pinrepair.com/sys1/#sys1poweron

Have you checked Q3 and Q4?

So your low voltage side is good, and that 42v depends on the 60v. So your Q3 might be the ticket. I would try the PN2222a, the Google says they are the same. Have you seen the very helpful schematic here?

http://www.stevechannel.com/system1PowerSupply.htm

On A2P1 (input from bottom board) 69v is across pins 6 and 7. DMM set to AC, polarity doesn't matter.

You can also check for 90v DC across C6, that will validate the rectifying diodes CR6-CR9.

Well at that point you're working with a network of transistors which is beyond what I remember from EE101. Have you checked the remaining caps? I had an issue where my voltage was slowly dropping after power up, ended up being one of the tantalum caps that was funky even though it tested to the correct value. Seems like C7, C9, and C10 have critical roles.

Your latest pic shows original C9 and C10. These are tantalum caps, usually only the electrolytic caps get replaced by default.

No, 69VAC inputs connect between CR6 and CR7, and between CR8 and CR9. They cross over that first trace without touching, as there are no dots where they touch (a dot is a "node").

Those diodes form a bridge rectifier to convert the AC to DC. Here is a description with an nice animation that will clear it up:

https://en.wikipedia.org/wiki/Diode_bridge

That's because the AC voltage is measured as RMS. Give this a read:

https://en.wikipedia.org/wiki/Root_mean_square

69V / .707 = 98V

You're getting a bad reading somehow, probably not a good clean conducting surface. Or you could have a cold solder joint depending where you're testing from. Since you have two readings I assume you're testing on the leg of the resistor itself.

Your 36V measurements are correct because you were testing from C6 ground. However, those nodes are simply the AC input and so should be tested by putting one test lead at each location. When you test from the DC ground you will get half the AC voltage.

36V + 36V = 72V <-- correct AC input

Your 101V is correct because of the RMS value of the AC voltage

72V / .707 = 102V