Sony KP53XBR15 convergence problem

[Guest]

Hi. Sony KP53XBR15. Red convergence - horizontal size adjustment - from
center to right works perfectly. From center to two thirds out to left works
perfectly. Far left one third is the problem. As size is adjusted down from
as big as it can get, just before it would be correct, far left part of red
image suddenly increases in size, running off left side of screen, while
rest of left side image continues decreasing in size.

Have replaced STK devices, even exchanging them to see if problem follows
chip. No.

Have replaced all low ohm feed resistors and checked all others. No go.

Not heat related. Does it hot or cold.

Have removed and checked all elec caps on board. No go.

Have checked power regs. No go.

Mind you, the blue works perfectly, as does the green.

I can't see it being the size pot.

I scope the red H conv output, and waveform does look different than the
blue, but on STK input I can't see any difference. Yokes read okay ohmswise.
I don't have a spare yoke or conv board to try in it.

Any constructive thoughts?

Thanks much, Danny

 

[Shoreline Electronics]

Fixed your model #...should be KPR.

I'd suspect the pot if your getting a drastic jump like that. Is there a
dead spot in it maybe?

--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
[email protected]
========================

 

[Guest]

Well, if it affected both left and right, maybe so, but it is dead smooth
movement on right side and inner part of left side. Just the far left side
is affected.

Danny

 

[Shoreline Electronics]

Do you think someone may have tweaked this set before you? These can be a
real headache if so. Too many pots!

--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
[email protected]
========================

 

[Guest]

No. I've known the set since it was new. Belongs to a friends inlaws. I
fixed the p/s a couple of years ago. This problem showed up like instantly
one day. No one else has ever worked on it, or fiddled with the convergence
board.

I also did swap around the little 8 pin op amps, there are like 7 of them,
but that had no effect. Was worth a shot.

Danny

 

[Ancient_Hacker]

Maybe one of the diodes? That's about all that's left.

 

[Guest]

Haven't found any bad, like open or shorted yet. There are 2 chips kinda
near center of board. One of them may be the problem. Just hate to throw
money at it until I have a firmer handle on the problem. The owner is in
south Florida for a month so I have some time. I don't have a print of this
board, may try and locate one if I have to.

 

[Guest]

Swapped CXA1268P chip, I believe IC912. Not in front of it right now, and a
16 pin chip whose number I don't recall right off, both borrowed from a Mits
conv board. Only 1 large size IC left on board. Am beginning to wonder about
the yoke.

Danny

 

[Guest]

Okay. Bad red yoke. Looking for good used one. New is prohibitively
expensive.

Thanks for the advice, Danny