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Fixed! It was a bad QL2. I had already replaced it twice with parts I got on eBay. Replacing with a Mouser part completely solved the problem. Other than the floppy, everything works now. If others have bad analog boards, I’d be happy to debug and fix them. I have so much hard won experience...

Congrats! I am surprised you had any picture at all. I had a bad LM317 and got nothing on the tube. Good to know.

Figure 2 is a zoom in of figure 1. Figure 3 is the 60 hz signal. I didn’t take a screenshot of the second 60 hz signal but i can do that.

Could you please post a good wave of pin 1? That is where I think my problem is. Thank you!

Here is the oscilloscope output at the deflection yoke for vertical and horizontal. Does anyone have correct traces I could compare to? Or feedback on whether this is clearly bad or not?

Since your last post, I managed to get an oscilloscope to debug my problem (similar but on the horizontal). I at first had trouble getting the 60Hz traces too, but I realized I just wasn't triggering on them. Adjusting my scope, I got the one on pin 4 fine. The signal on pin 3 is the same...

Nice! Let us know how it goes. The one other component to check in that area is the capacitor connected to QP6. I took a look at the size of the resistor you are blowing and it it looks like a 1/4 watt or smaller -- it would definitely would burn out if it was connected between 29V and ground.

But in your first message, you say you got a good 60Hz wave on pin 4. That is what I am confused about.

It seems strange that you get a good 60Hz signal out of pin 8 but don't get a 60Hz signal in from the digital board at HS1. I was reading this thread on VCF, though, that discusses debugging this area of the circuit and could be useful...

I'm assuming you are on the second board revision of the analog board, and RP48 is connected to QP6 which goes to ground. Talking to my EE friend, the most likely short that would burn RP48 given the schematics would be between the 29.5v on one side of RP48 and the ground connected to QP6 on the...

Do you get a good 60Hz signal at HS1, the vsync signal from the logic board?

Confirmed my QL2 was the problem. Replaced it and it now displays.

Sounds like similar but opposite problem to what I just posted about. Did you ever find the cause?

See attached photo. I tuned it with the seven pots as best I could. It has been cleaned, recapped both boards, etc (separate thread on that) to get this far. Is anyone familiar with this problem? Without knowing what I am talking about, it feels like it isn’t scanning all the way across. Maybe...

I solved it! Replacing the QL2 (IRF740 power MOSFET) with a new one from Amazon (Anchor Electronics does not stock this, sad Mac...), and putting everything together, I get a screen! Now I need to: 1. Get a keyboard! I wasn't sure I would get far enough to need one. Anyone in the CA Bay Area...

Progress! I found at least one problem. After removing QL2 (the IRF740 power mosfet), now I get 30.7 volts at the expected locations. I tested the transistor and it is definitely not switching, so I have a new one on order arriving tomorrow. Who wants to guess what problems show up once this...

Did you ever figure this out? I have a new thread with the same problem and am narrowing in on QL2 as one potential problem.

Update: my problem definitely is linked to not seeing the 30.7v DC supply voltage. Today I checked everything around and including the IP2 LM317T voltage regulator. All the caps are new and correct orientation, resistors all good, and DP13 good. I replaced IP2 as well. Still no 30.7v. Next the...

Thank you, I think I am heading on the right track now. I am going to dig deep into this with an EE friend and try to figure it out. I found and verified all the voltages on the power supply side of the AB with them (+306v measured +323v, but the others +38v, +12v, +5v, -12v are right on), so...

Oops, board revision 630-0525-8, and I misread the schematics. It is pages 4-6.