K4600 (19K4625) Low B+ Measurement

shawncruiksh

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Donor 8 years: 2018-2025
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I've got a K4600 that's flickering. B+ measures 115vdc, and should be 127vdc. VR501 won't let me adjust above 115vdc.. The chassis was recapped probably 6 years ago, and all caps look fine. I've tested all components on the little side power board, and side transistors (TR501 and TR502) — all fine. TR502 initially had a low hFE, so I replaced it with a fresh one - no change beyond needing to adjust the vsync.

There doesn't appear to be any cold solder joints, but will check in detail.

I noticed the manual has VR501 as 81k ohms, and mine has a 1k ohm potentiometer from APAR and @security0001. Could this be the issue?

Anyone have any other thoughts on areas I should check?
 

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It's 1K. All the trimmers in the schematics have a B (that is easily mistaken for an 8) before the resistance value.

81K wouldn't make sense btw...
 
That's a B1K (1K) not 81K so you have the correct pot.

Has the paper cap at C621 been replaced? Flickering is pretty common when that cap starts to go bad. If it hasn't try lifting one leg of the cap and see if your issue goes away.


This part will also work

 
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