PT56WXF95A next steps after STK replacement

[bhalpin]

In my previous thread on this topic in the DIY forum I asked if my problem could be an STK issue.

http://www.hometheatershack.com/foru...tml#post180946

I asked because I've just replaced the two STK390-040 chips and four crispy resistors in my nine year old Panny PT56WXF95A and have some residual issues.

Unfortunately I had not found this forum earlier and had purchased my STKs off of eBAY.

The picture is back from its once miniscule size, but I have an issue with the blue gun. I haven’t determined yet if this is an issue with my repair workmanship, perhaps I installed a defective eBAY chip, or if some other piece of the convergence/geometry system is amiss.

I have not changed any service mode convergent adjustments at this point, because I
believe that I still have something else wrong and don’t want to move too far from factory settings just yet.

The B-H adjustment cannot be brought into alignment with the crosshair on the user convergence screen by about a half inch. I do have a range of adjustment in both directions, however, it is offset to the right of where it should be. In addition the blue raster is smaller than it should be and somewhat compressed and jagged on the left of the screen. The green and red convergence are fine, as is the B-V.

Since the crispy resistors were also associated with the B-H convergence, I am focusing on that path. It could very well be that I have a defective amplifier in the chip the I installed. I’ve carefully inspected the PC board for solder shorts and have hunted around a bit for other obvious issues. Wouldn’t know this much without the schematics from the service manual someone sent me.

When I started out, the picture was totally collapsed and unrecognizable. After replacing the STK chips there is a picture on the screen, but with the blue convergence and size off. You can see better on the “self check” screen and on the predominately blue Cox logo screen below that the blue image is trapezoidal and comes up short of filling the left side of the screen.





I have an old Simpson VOM that I used to check the four 10 Ohm resistors and to check continuity from the STK pins other components. I didn't measure the supply voltages to the STKs either since five of the six channels seem to be working just fine.

I have assumed that after replacing STKs that I should have been in the ballpark with the convergence on all three colors. With the blue being so far out, I'm questioning if something else (self inflicted or otherwise) is wrong.

The attached Service Mode picture below is where we currently stand.



Is it advisable to tinker with the size and linearity given that the convergence chips were replaced?

All inputs are appreciated.

Regards
Bill

[lcaillo]

Sorry I am so late responding.

I would double check your work and look for open resistors. If not, you likely have a bad IC. You likely will need to touch up convergence after replacement, but not this much, generally.

[McGregor]

I have a semi-similar issue and i'm not sure if it is a bad convergence chip (or both chips). Or if I am unable to focus the tv properly. What is happening (and i'll update with a screenshot as soon as i can) is the blue image lines up everywhere but on the left side. It's slightly to the left (about 1/3"). If I use the convergence adjustment on the tv and line the blue up, the left side is slightly off. If i ignore the convergence box and move it to the right the colors line up to the image (xbox 360 is what i used for picture). This results in the convergence box being way off and the rest of the image is blurred because of it. Is this also related to either a bad convergenc IC or a bad solder somewhere on the board? I didn't replace any of my resistors (none looked like they needed it), is it possible I have a bad resistor on the PCB? Thanks for all the help so far!

[lcaillo]

Are you adjusting the consumer convergence or are you using the service level convergence?