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I wouldn't fiddle with the RAM slots unless they were visibly bad, though some deoxit might be advisable in any case. Just to be sure you're getting consistent behavior, I'd lift R7 and short pin 5 to 6 on the footprint for UB11, so you can manually reset the machine at power-on and guarantee...

The filament is separate from the HV. Sure, both are generated by the flyback, but one can fail with the other working. See if a piece of paper will stick to the screen when you turn the machine off/on.

Ah, there, I forgot how that was wired. Shoulda looked at the schematics but on the phone that's no fun. UB11 and the m68k are the only things able to drive /RESET in the whole machine. Of course, nothing to stop a pin on any of those other ICs being shorted, but as far as actually being meant...

I wouldn't bank on parts being exchangeable. Apple has always been annoying about one or another thing not fitting (I learned the hard way some 15" Aluminum PowerBook memory doors aren't!). Your existing machine should be fixable, anyway.

What is that suspicion based on? Back to basic steps: do you have HV? (Can you feel the screen pull the hairs on your arm?)

Yeah. Apple was weird. The PowerBook Duo standalone battery charger (what clips on the side of the power brick) is essentially PG&E by itself in a case with some power electronics. But that's derailing the thread :)

@Arbee PG&E machines with trackballs use ADB for that internally. Ditto for trackpads on 190cs and up. Thus, the whole of ADB not working would result in those symptoms (no pointing device) without interfering with keyboard operation. I would check that the ADB data line isn't shorted to ground...

Hmm, I forget - isn't the reset button wired into the /RESET line directly? If it's wired into pin...6 I think, of UB11, then yeah, it shouldn't work. I never understood Apple's decision of bunching power-on reset together with audio.

Pressing the reset switch is a viable alternative. I think that's only if it's never asserted - with reset stuck low, it should be a brick.

It'll run alright without them, absent any other faults.

Weird, but not entirely unheard of, having both Sony chips fail. Solid troubleshooting effort thus far. Pulling UB11 and looking at /RESET again will soon tell you if that was your problem.

Ugh. Ewaste bin rash on something like this saddens me. Nice save. Even the broken SIMMs have value IMO - I have a small box of SOJ waiting to be repurposed.

Sure, that'll work :)

If you mean DP5, they're NOT identical parts (DP7 is the only EGP30D in the machine). DP5 is a BYT03-300 according to Bomarc.

Uhm, I don't recall. But I think you're right in that it was supposed to be one of the "what's the Mac II gonna look like?" ones. Might be in one of those spec proposal papers?

https://www.mouser.com/ProductDetail/onsemi-Fairchild/EGP30D?qs=sEr9WmQGXZabTAKVOEB3mQ%3D%3D An exact match - whatever your favorite source for an EGP30D is also works.

630-0525 is the PCB itself, 820- is the whole assembly, so we're on the right track :) Certainly an odd pattern...

Digging out some stale projects and getting them to where boards can be made

If your analog board is P/N 820-0525-A, check DP7, LP5, CP8 and CP12. If anything I'd bet on DP7.