Peale
Active member
took in a 25K7000 for repair. All original caps and fly. Original complaint was about pincushion and other picture issues.
This is P538 chassis, with the pincushion board.
On initial exam the flyback was cracked, and several of the caps were bulging. I didn't even bother with an initial test, I dove right into caps/fly.
On power up I noted that the top 1/2 of the screen appeared to be perfect, while the bottom was only drawing one scanline every centimeter or so.
I twiggled and twiggled and suddenly...I had a perfect picture. Very odd. So, I kept twiggling...and suddenly I had vertical collapse!
Convinced that I had blown the vertical IC, I ordered a couple of replacements. While I was waiting (for the LA7833) I did find one on a TV chassis. Once I replaced it, I turned all of the pots to their lowest setting, and powered it up. bringing up the screen control I could see that I had a very small picture of some kind, and once I started to make adjustments, I was back to where I started with the 1/2 top good, 1/2 bottom spaced.
And then...poof...vertical collapse, again.
I stood there for a few seconds, then turned the vertical sync back a notch, and *poof* it came back.
With more adjusting, I had a perfect picture. It's running like that, right now, with a Klax board. I know it's not fixed by any stretch. Any ideas? I've never heard of selective vertical collapse.
This is P538 chassis, with the pincushion board.
On initial exam the flyback was cracked, and several of the caps were bulging. I didn't even bother with an initial test, I dove right into caps/fly.
On power up I noted that the top 1/2 of the screen appeared to be perfect, while the bottom was only drawing one scanline every centimeter or so.
I twiggled and twiggled and suddenly...I had a perfect picture. Very odd. So, I kept twiggling...and suddenly I had vertical collapse!
Convinced that I had blown the vertical IC, I ordered a couple of replacements. While I was waiting (for the LA7833) I did find one on a TV chassis. Once I replaced it, I turned all of the pots to their lowest setting, and powered it up. bringing up the screen control I could see that I had a very small picture of some kind, and once I started to make adjustments, I was back to where I started with the 1/2 top good, 1/2 bottom spaced.
And then...poof...vertical collapse, again.
I stood there for a few seconds, then turned the vertical sync back a notch, and *poof* it came back.
With more adjusting, I had a perfect picture. It's running like that, right now, with a Klax board. I know it's not fixed by any stretch. Any ideas? I've never heard of selective vertical collapse.
