Sony Wega KV29FA210 Screen defect // Help

[vdorza]

Hello All I´m in need of help. Today i noticed this defect on my 29" Sony Wega(KV29FA210). When using the 240p test suite (grid pattern) i see that the squares are deformed on the upper corners of all squares in the grid (not the borders of the screen). Its like they are slightly bent to the left. Otherwhise the tv is fine, the colors are vibrant and the convergence is still good. I recaped almost the entire main board, and some capacitors in the power supply board and the neck board.
Any help will be greatly appreciated.

 

[betwixt]

Otherwhise the tv is fine, the colors are vibrant and the convergence is still good.

That doesn't make sense - the fault is bad convergence!
I think I would like to see the same image with the red gun turned off, it isn't clear whether the problem is lack of blue/green at the edges (a blanking fault) or just the red E-W amplitude is wrong.

Brian.

 

[vdorza]

Thanks for your reply. When i turn off the colors (in the service menu Red off/ green off / blue off) the problem tends to dissapear. I will post pictures in a while for you to see.

 

[vdorza]

Here are the pics with the colors off (one for each color).

 

[KlausST]

Hi,

I'd say it's a power supply problem for the horizontal deflection part.
It may be a GND connection problem, too...in the horizontal deflection area.

Use an isolating stick to gently move some wires...while you look on the screen (with a mirror) to see if something changes.
If it changes, then it's most probably a bad connection...try to locate it...
If nothing changes, then check the power supply for bad (old, bloated) electrolytics capacitors.

But maybe it's someething different...

Klaus

 

[betwixt]

Strange! The problem seems to be that the red works properly but the blue and green levels drop suddenly at both sides of the screen and at the top and bottom. Given the nature of CRT systems, my first suspicion would be the cross hatch generator rather then the TV!

Its a puzzling combination of symptoms, I think i would start by looking at the blanking pulses to see if there is something common to the blue and green that doesn't also affect the red. Possibly a broken PCB track or bad joint on the CRT base or video driving circuits.

Brian.

 

[vdorza]

Hello guys, thank you for your replies. I have one more piece of info that may help (or not) to solve this puzzle. In she service menu there is an option called AFC. Its value can be set between 0 and 3 (0 is the default). If i go all the way up to three the problem almost dissapear and the lines become straight. BUT, the overall image seems to be a little unstable.

 

[KlausST]

Hi,

maybe TI´s AN-656 (snla017.pdf) can help.

Klaus