LG 60PX950 ~ Vertical Pixelation Issue

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

No point changing the potentiometer it can only go 10% higher/lower.

You need to find what's pulling the vsc down. I'd say you probably have quite an obvious short somewhere.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Do you think the source of the pull-down Vsc voltage lies on the YSUS board itself, given the fact that I'm getting proper voltages from the PSU to the YSUS connector?

Can we rule out the logic board, main board, and all of the others?

Where would you start to test, Hamie?

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

By the way, the green pixelation upon startup that I had been referring to as "vertical" is really just being caused by the appearance of the LG logo (a rotating cube) as it passes from left to right on the screen and back again. I found this video on YouTube that illustrates what I mean.

https://www.youtube.com/watch?v=7QYd2U3JeWo

Skip to the 3:00 minute mark in the video to see the logo moving.


So, it's not as much a vertical picture issue as it is an overall voltage issue, apparently.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

I have the day free to work on this television, so help from anyone out there would be greatly appreciated. Thank you to Hamie and to anyone/everyone else.

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

From the information you've told us it would appear that your problem is the y-sustain.

So pull the board out and take some good photos of the top and bottom sides.

Check to see if any IGBTs or DIODES mounted to heatsinks are shorted. Check all fuses and fusible resistors to see if any are open. The main fuse will be fine since its getting power but there are more you'll need to check.

Please don't start desoldering parts. If there's anything suspect just post it and someone will respond.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Okay. Will do with the front/back pics of the YSUS.

As a side note, I disconnected the Lower Y-Buffer only this morning and powered it up. I expected to see the pixelation only on the top half of the screen, but in fact it started to run the same left to right sequence and the green pixelation still ran from the top of the screen all the way to the bottom. I only left this plugged in for about 10 seconds, as I didn't want to damage the upper buffer board or anything else.

With what's going on re: the Vsc voltage, was this to be expected, even with the lower buffer isolated?

And, there is a long/short, long/short followed by about 3 seconds of no light (then repeats) on the green light on the control board. Not sure if that's normal or if it's an error code. If it's the latter, maybe someone could point me to a listing of the error codes for this particular set.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Here are the detailed pics of the YSUS, front and back.

Hopefully they will come through with the image right-side up.

If anyone spots an issue, please let me know both where it is and how to diagnose/attack it. As of yet, I haven't had to go to the level of diagnosing any of the YSUS boards on previous sets I've worked on. So, I appreciate any guidance that can be provided. Thanks.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Well, it looks like all of the images above got posted with a 90 degree rotation to the left, but that's okay.

Here are 8 more images, taken from different angles:

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Have you checked the heatsinks for shorts?

Check and see if the vsc test point Is low ohm to Gnd.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

I don't see anything that is broken or burnt on this YSUS board, but maybe someone else will. I also want to make sure that this problem is not really originating from the control board or another board, before attempting to fix the YSUS. Does the blinking code I mentioned above in Post #26 mean anything?

Another piece of info: Regarding the Y Buffer Boards, I placed the DMM probes onto the six, small black elements (see center of pic) that sit adjacent to the six IC's, and obtained the same readings on all six. Is this enough of an indication that the Y Buffers are okay or will they need to be tested further?

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

I'm not sure how to test the heatsinks, Hamie. Can you guide me on how to use the DMM here?

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

The problem is the y-sustain.

It would appear vsc is shorted to ground.

Hence why it's missing.

You don't need to concentrate anywhere else. Untill you have 150v at vsc the tv isn't going to work.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Okay, that's good to know. I'll focus on getting that 150 Vsc reading.

Can you tell me how to test the heatsinks? Or, point to a video or tutorial that does the same?

Also, I'm not exactly sure what you meant by:
"Check and see if the vsc test point Is low ohm to Gnd"

In need of a little step by step guidance so I can progress. Thank you.

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

I don't know what meter you have but I assume it has a buzzer mode.

Ie: you touch to 2 probes together and it gives a continuous beep?

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Yes, it has a continuity mode where the touching of the probes produce a continuous beep.

I used that mode to test all of the fuses, which are all ok.

I also got the continuous beep (continuity) when I touched the leads coming off the three large copper coils. This was done with the board completely off the back of the set.

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

OK so everything attached to heatsinks, see if any of the IGBTs are buzzing in ALL directions. If any are they are almost certainly shorted.

Make sure you test the ones under that thermal pad.

You don't need to remove them from circuit. Just turn the board over and touch the pads

Note: some might have 2 pins tied together so they will test shorted but may be OK.

For now concentrate on finding one/s that are shorted in all directions.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

And, I put the probes on the triangular shaped leads coming off the back where the heatsinks are. I tried to mark up a photo of the results. Here are the numbers I got:

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

The numbers in the image above were obtained with the DMM in the shared Continuity/Diode mode. See image below of the Sears Craftsman Digital Multi Meter I am using

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Under the foam pad?

You seem to be over complicating things here. We just need to know if any of them are shorted... Ie buzzing in all directions.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

OK so everything attached to heatsinks, see if any of the IGBTs are buzzing in ALL directions. If any are they are almost certainly shorted.

Make sure you test the ones under that thermal pad.

You don't need to remove them from circuit. Just turn the board over and touch the pads

Note: some might have 2 pins tied together so they will test shorted but may be OK.

For now concentrate on finding one/s that are shorted in all directions.

----------------------------------------------
Nothing was buzzing, but I don't know how it would be as I have the board off of the set. Do you mean by placing the board back on the set?

I didn't test under the thermal pad, but I will do that next. Are the readings I posted in the photo above the correct way to read whether these heatsinks are in working order? Or, am I off base? Nothing related to the heatsinks that I tested before produced the continuous beep, which would have happened if they were shorted, correct?