k4600 focus is pulsing

mrbill2084

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A friend brought over his afterburner 2 for me to look at. I got it working, pic looks good, but the focus on the k4600 looks like its pulsing. It probably needs caps. But I think the focus is a different issue.

Any ideas? Bad flyback or bad focus pot?
 
I would guess the flyback, but there's a small cap, wrapped in electrical tape that attaches to the focus pin on the neckboard. That may be your problem.
 
thanks, I will check the neck board cap when I recap. Nice thing about 4600 its easy to swap the flyback with another 4600 chassis.
 
I recapped it. It fixed some display linearity problems, but it was plusing the focus a bit less. I dug out another 4600 chassis that was working a few weeks ago, swapped the flyback, and it had no video.

So to check if I messed up the main part of the original chassis, I put the orignal flyback back in and now its pulsing the focus more than before. So shaking it up a bit during the transfer made it worse.

I am going to put back together the spare chassis to see if its still working. I will dig out another tube and try testing the 4600 chassis in that.

update: After fixing another 4600 chassis with similar results, I dug out a 2nd 4600 tube. Problem is in the tube. When re-checking the neck for a bent pin, I found the ground pin loose. Tube socket was holding it in place.
 
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