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Tek 603 - recapped LV board, now moving on to other problems. Advice on -30V reg?

toby@...
 

Hi,

I've been working on a 603 XY and began by recapping and testing on
Variac, which cleared up display bloom and a squiggle.

What I have now is:
* a somewhat defocused (2-3mm), very bright spot
* unresponsive intensity control
* focus control has effect but cannot focus spot

All the above seems to indicate a HV issue. I am waiting on a HV probe
so I don't have a measurement yet. But, possibly related:

Was not able to bring the -30V into spec, rails currently measure
+215: about 250
+15: about 17.7
-30: about -36

The -30V adjustment is R878 trimmer but it has no effect on the voltage.

I'm looking at the regulator section schematic, I've checked the VR870
zener and it's nominal ~ 6.2V.

I'm pretty new to repair so I was hoping for a pointer or two to where I
could look at re this initial inability to regulate or trim -30V.

I believe this is the most relevant part of the schematic:
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

--Toby