577 D2 Display Issues


@gmilliorn
 

I've been trying to restore a 577 D2 that had several problems. The
previous owner(s) hacked up the -12V supply and the regulator was floating,
unheatsinked. The 200V fuse was blown (cautiously replaced, no issues
so far), sticky switches (cleaned), excessive ripple (recapped). After
all that I got the stairstepper working and get the mostly correct display.

There's a few odd issues though:
* Every 1-5 seconds there's a brightness flash on the traces. There's
nothing seen on power supplies or main boards that correlates.
* Focus is sharp but intensity ranges from low-high-low.
* HV is limited to -3362V max (or min?), but should range -3270..-3570.
* There's black soot on the inside of the HV shield as well as the back
of the yoke connector (I can see someone's thumbprint). Not sure
how that happened, but it was in two physically separated areas.

So it mostly looks like an HV issue, but that odd flash makes me worry
it could be the tube. It doesn't appear to have been replaced, despite
the thumbprint. Does any of the above point to one or the other?

Thanks,
Gary

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