K4600 wobbly picture

gleegum

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Donor 2018, 2025
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Got this K4600 that wasn't working. It had several cold solder joints. I've reflowed them and did a full cap kit on it. I have a picture now, but it's unstable and too blue.
B+ was at 123 VDC. I tried to adjust it, but I can't reach 127 VDC; the closest is 126 V. The problem is that the closer it gets to 127 VDC, the more unstable the picture becomes compared to 123 VDC.

Here is a video with B+ maxed out at 126 VDC: https://photos.app.goo.gl/vmPXtJCMDnyJhsRE6

I have another K4600 that I'm not sure is working, but I was going to swap the regulator board until I saw that it had a C1723 transistor, which the other board doesn't have, and it doesn't have a diode across the regulator.
I've attached pictures comparing both.
Are they swappable?

For the 'too much blue' color problem, I swapped around the neck board transistors, but the problem persists. The tube tested fine in my tube tester with no shorts.

Any help is very appreciated.
 

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I swapped the tube with another K4600 tube, and the blue color issue went away, so I guess the tube tester is not as trustworthy as I thought.
I'm now able to adjust B+ to 127V, but the picture is very wobbly and has curved borders (pincushion?), mostly on the left side.

The B+ changes depending on the picture shown. Is this normal, or should it be a steady 127VDC?

EDIT:
Just swapped the XY and video boards and the problem persists.
 

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