Finally fixed an MPU board that had me tearing my hair out.
-35 board, running 2732s, only had 3 flashes. Everything points to U10, but he's good.
Probing around with the o'scope following data lines, D7 was flakey.
Further testing with a meter finally isolated the problem internal to the socket. No continuity through the socket.
Replaced socket, runs like new.

Next board: No VMA, but U9 is good. U19?

Tic-Toc, Tic-Toc.
I'm thinking maybe U19 might be loading vma down?
I'll get on it tomorrow.

Yes
Yes
Yes
Not good clear stuff, look like noise/ garbage on the o'scope
Very mild, been cleaned and treated
VMA is locked hi, 5vdc.

Mini boot, (u9,6,11) has no flicker.

So, I tried isolating pin 5. VMA was there for a half a second, then stuck hi again. Tried it with 2 different cpu chips, same result.

Address lines are doing that with all chips in. Data lines still look like trash.

Thats what it looks like.
U15-3 is pulsing, but it just clockphase2, as U15-4 is always hi

I still can't understand why VMA won't work when it's isolated.
Good chip signals at U6,2

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Corroded areas have been treated with ACF-50.
It's an aviation thin-film anti corrosion product I've used for years.

I'll check the ground plane.
I've used those roms for years.

Hey Eric! It's Jim Hursey. How you been?
We're in Fl now. PM me.

Repaired the ground plane. Board booted right up.
Still would like to know what that had to do with VMA, but what the hey.
Thanks Quench!