LG 60PX950 ~ Vertical Pixelation Issue

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

The connector between the two Y Scan Boards, as seen in the 4th picture above, seems to be locked in tight. So tight, in fact, that I had a lot of trouble removing it at all and never ended up doing so. I wanted to see what would happen if I re-seated it. Could that connected be a suspect in this scenario?

You can see the two wire-pronged connectors that lead from the YSUS Main Board to the two respective Y Scan Boards, also in the pictures above. That lower connector is the one I had off when I was getting the top half of the picture to come through.

The picture you see below is just one of the small black components (all labeled D202) that rest on the Y Scan Boards. There are 3 of them per board (so, 6 total). Thing is, they all read the exact same on the 200 Ohm setting on my DMM (all six read 10.3), and they also all show continuity (beeping) and read 010 when I set the DMM to the Diode/Continuity setting.

It seems odd to me that the lower scan board would not be operational under these circumstances and with these readings. When I was working on my year 2006 to 2008 Hitachi P50H401's, whenever these diodes obtained the same readings as related to all 8 IC's on each Y scan board, that's how I (generally) knew that that particular board was good and ready to display a correct 1/2 screen image when I plugged in the set. And, that rang true every time I did it.

Question now, I guess, is:

On this LG 60PX950 plasma, can the IC's be defective even if all of these D202 diodes are giving the exact same consistent results / readings?

[freakaftr8]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Okay then that lower board is shorted those green scan lines you're getting are showing which Ics are shorted to ground.

You're getting a short in those diodes reading both directions due to the fact that one or more skin drives are shorted. It is acting as if you put a wire in Bridge series shorting the scan output drive to ground

Do you get the same readings on those diodes on the upper board

I should note that the green lines you are getting on the screen without the voltage being applied to the board is almost indicative of where the short lies within the scan ics

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

In answer to your question up above, yes I am getting those exact same D202 diode readings on the Upper Y-Scan Board. The three on the lower board and the three on the upper board all read the exact same thing. That's why I am thinking that this lower board still might be functional in some way where I can bring it back to life.

So, I don't think there is a short in any of these D202 diodes. They are all operating in the exact same manner, apparently. For the exact readings, please see Post #61 above.

Can you confirm for me, definitively, that the IC's on this lower scan board can be shorted, even if all of those D202 diodes are reading properly? Or, is it possible that the problem lies in the small, white connector that bridges the Upper Y-Scan and the Lower Y-Scan and brings them in connection with one another? (See image below)

Note: I found a lower Y-Scan board online for only $35, and will order it now if you confirm that the IC's are definitely defective on this lower Y Scan Board. Very good price, but I'd still hate to spend any money on it if the one I have can be resurrected in some manner.

One other note: When I hooked the lower Y-scan back up to the YSUS Main board just now, and keeping the upper Y-scan board connected to the YSUS Main board as well, the entire screen goes black once again. Is that the expected result? Seems like the potentially defective lower Y-scan is disallowing the upper picture to appear.

[freakaftr8]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Well then there's probably a return circuit built in to this circuit where the diodes are . you might get a different reading if you remove the buffers from the ysus. But none the less those diodes are supposed to read that way. The Ics on the board are the ones that are shorted. I would just get a new buffer board as they're relatively inexpensive and you don't want to take the chance of destroying your ysus as it sounds like you got lucky so far.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

I agree.

Pretty lucky so far. Okay, I will order the new lower Y-scan board and will update this post after it arrives and is put into commission. Thank you for the pointed advice, and thanks to all who contributed to this thread.

~ David

[freakaftr8]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Your welcome let us know

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Waiting for the new lower Y-Buffer to arrive.

Still wondering if the Y Main Board is functioning properly, though. I am still getting odd readings on some of the resistors on the bottom half of it.


Only 1.3 Ohms vs. the expected 2.2 on two of the resistors (see picture) ~~~ Markings on these two are both Red, Red, Gold, Gold

and

Only 161K vs. the expected 220K on the 2 Watt resistor also shown in the picture ~~~ Markings on this one are Red, Red, Yellow, Gold


Important note is, I am getting only 1.2 on two Red, Red, Gold, Gold resistors that rest on the ZSUS board as well, indicating that this might indeed be okay.


I don't want to put the new lower Y-Board in when it arrives if the Y Main is still compromised, as it might blow out the IC's in the new buffer board. Maybe these suspect resistors caused the original lower board to fail?


QUESTIONS:

1) Would the top half of my picture be appearing so flawlessly if the ZSUS was compromised in any way? For, if it isn't, then the two 1.2's on the YSUS might be just as okay. I'm guessing that these are indeed okay.

2) Can the 161K reading be responsible for the lower half of the picture not appearing, while the top half indeed does?

3) Should I wait for the new lower Y-Board and then just risk putting it in? Or, should I replace the three resistors you see pictured below before coupling this Y Main with the new Y Buffer?

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

if youre getting a perfect image with the shorted buffer removed and vsc and vy now correct i wouldnt concern yourself with the y-sustain any further.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Okay, that's the way I am leaning too.

Just not absolutely sure that the original lower really is shorted. It might be malfunctioning because of the faulty resistors on the Y Main, no? All of the diodes on the lower buffer are testing exactly the same as on the upper, leading me to think that this lower board still might be okay.

How do I know, or how can I tell, if the lower board is truly shorted? Can't physically see the IC's in this model to see if there are pinholes in the top of them like I could with the earlier model Hitachi's I've worked previously.

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

post a picture of the buffer

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Here it is:

(Let me know if you need a better image)

I also included a close-up image of one of the Y-buffer diodes I tested. There are three on the lower board and three symmetrical matches on the upper. They all test exactly the same.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

The other thing that's quite a bit different that the Hitachi's I worked on before is that when one of those IC buffers blew out, there would be a definitive "patch" of green, horizontal lines that went across the screen. This patch would be at least 4 to 6 inches high from top to bottom. In other words, it was rather large and distinctive.

The green lines I am not getting on the bottom half of this LG 60PX950 are very thin and very scattered. There does not appear to be a distinctive pattern to them.

Please check out this video to see what I mean:

https://www.youtube.com/watch?v=ycYK...ature=youtu.be

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Also, Post #56 in this thread has a few more images.

I also tested for continuity between the Y-Buffer's main connector (the one that connects to the Y Main Board) and all of the pins on each of the 4 ribbon cable connectors. No continuity was found. On the Hitachi's, when an IC was shorted, I would get continuity when testing in the same fashion.

[attainteddragon]

Re: LG 60PX950 ~ Vertical Pixelation Issue

with your buffer board removed.
put your dmm in diode mode.
place your positive lead on ground and slowly run your negative lead down the contact pins that attach to the panel. (tou may have to do the inner pins too)

you will soon know how many lines in each buffer chip that have failed as you will get a continuity beep on each failed line. a good line will give you the normal reading around 700.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Did that, but found no continuity. The new board came, so I decided to put it in and see what happened.

Now I get no picture whatsoever. Just black screen. This is now the case with both buffers connected to the Y Main, AND with only the upper buffer connected (which is particularly disturbing because that's the scenario whereby I was getting the top half of the picture to show up yesterday).

I've decided to pull the Y Main Board out and replace both the VSC resistor and the VY resistor, as I was getting very low voltage readings right before I pulled it that were fluctuating on both resistors. They have never read close to 100 Ohms, where they should be, so I am going to see if the new ones will consistently give me that reading both with no power applied and with the tv's power on. If so, I am hopeful that the Y Buffers are not damaged and that these poorly functioning resistors are the real source of the problem.

Does anyone know if a resistor's performance is Y Buffer Dependent? I am asking in the sense that it even though it's reading lower than expected (59K vs. the expected 100K) on the Ohm scale that it might indeed function and function well if only 1 Y Buffer is hooked up, ....

but if BOTH of the Y Buffers are hooked up simultaneously it might overtax the already strained resistor and thereby prohibit both buffers from illuminating the screen and forming a picture on either the top or the bottom half of the screen.

Related notes:

• I'm still getting an expected 202 volts on the Vs from the Power Supply to the ZSUS
• And, I'm still getting 202 Vs and 59 Va from the Power Supply to the YSUS

So, both of those still look good

• Also, you can ignore the 161K vs expected 220K on the resistor I noted in posts above. I set the DMM all the way to 20,000K and am now getting 222K on that resistor. All of the resistors on the Y Main are now giving me correct readings except for the VSC, the VY, and the two Red, Red, Gold, Gold's on the bottom half that are still reading 1.3 Ohms instead of the expected 2.2.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

UPDATE:

I put the two new resistors in, and the readings are essentially the same as before.

Old VSC = 59 Ohms
New VSC =58 Ohms

Old VY = 43 Ohms
New VY = 42 Ohms

So, my conclusion is that these two are linked in such that you add them up to get to 100 ~~~ 58+42 (It's 100K, actually, because the resistors are each labeled Brown, Black, Yellow, Gold), but I'm just calling it 100

Unfortunately, there was no change in the picture when I put the Y Main Board back on the set and plugged everything back in. It's still all black. I was hoping that maybe the old ones had formed cracks in the solder joints or something of that nature.

{I didn't change out the 1.3 Ohms on the lower half of the board that I thought should be reading 2.2. Maybe I'll do that, but for the time being I am assuming that they, too, are tied together in terms of adding them up together. Basing this on the fact that there are two on the ZSUS that are side by side and are doing the exact same thing.}



Also checked the voltages of the VSC and -VY under the following conditions:

With both buffers disconnected from the Y Main: VSC was 150 and -VY was -180 (right on target with both)

With the upper connected and the lower disconnected: Both VSC and -VY were way too low and fluctuating
With the lower connected and the upper disconnected: Again, the VCS and -VY were both way too low and fluctuating
With both buffers connected, also way too low and fluctuating

At a bit of a loss. The easy conclusion is that now BOTH of the buffers are malfunctioning. But, I have a feeling this is not really the case. And, I can't afford to simply buy two new Y Buffer boards and hope and pray. Does anyone have any ideas as to why else the VSC and -VY readings would now be out of whack, given where I am at with this set?

Note: Interestingly, when both Y buffers were connected, I measured the 2.2 Ohm resistor that sits directly underneath the VSC and -VY resistors, and that one was no longer stable as well. It was too high (4.8) when I had the probes one way, and way too low (0,1) when I reversed the probes. When it was functioning properly (i.e., when the top half of the picture was showing up correctly), then I was getting a consistent reading of 2.3 or 2.4 at the most.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Decided to put the old (original) lower Y-Buffer back in to see if I could get the top half of the screen to appear again.

No such luck. i re-created all of the former conditions, and tried it both with 1) the upper connected / lower disconnected, and 2) with them both connected.

Just getting the black full screen still, as a result of the VSC and -VY voltages both being especially low (between 0 and 30) and both fluctuating. The reading on the 2.2 Ohm resistor that sits below was also off and was fluctuating.

Is it possible that the capacitor that sits just directly below the three resistors in question is malfunctioning, and causing all of this havoc with the resistors themselves (see image below)?

Seems like either both Y-Buffers are shot now, or something on the Y Main is dragging down the voltages. Not a great setback, but I'm not willing to give up at this juncture.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

A couple of posts ago, I wrote this:

Note: Interestingly, when both Y buffers were connected, I measured the 2.2 Ohm resistor that sits directly underneath the VSC and -VY resistors, and that one was no longer stable as well. It was too high (4.8) when I had the probes one way, and way too low (0.1) when I reversed the probes. When it was functioning properly (i.e., when the top half of the picture was showing up correctly), then I was getting a consistent reading of 2.3 or 2.4 at the most.


Now, I tested the same expected 2.2 Ohm resistor (please see the image below) with both of the Y buffers DISCONNECTED, and got the same results noted above (too high with the probes one way, and too low the other way 4.8 and 0.1, respectively).

Importantly, it has correct reading of 2.4 when no voltage is present.


It seems to me that this resistor is either problematic in and of itself, or it is malfunctioning when voltage is applied as a result of some other component(s) which are NOT the Y-Buffers .... as those are disconnected from the Y-Main now and taken out of the equation.

Adding to this theory is that I tested both the old (original) lower Y-Buffer for continuity as well as the new lower Y-Buffer that came in the mail the other day and neither seem as though any of the IC's are fried. Both tests were done when the boards were completely out of the set and attached to nothing. The red probe was on ground, and there was NO evidence of continuity on either the old or the new Y Buffer when I pulled that black probe across all of the pins (both the outside and inside pins). Also, all of the diodes on both old and new are giving the same reading of 492. In other words, there is no evidence that either of these lower Y-Buffer boards is defective.

I am going to replace and resolder that 2.2 Ohm resistor with (another) new one to see what happens. If that doesn't fix anything, my latest question is:

Which other component on the Y Main Board is most likely to be causing this 2.2 Ohm resistor to fail, but fail ONLY under voltage?

[attainteddragon]

Re: LG 60PX950 ~ Vertical Pixelation Issue

you should be doing your resistance measurements without power applied.

if you think that it if failing under load, check the dc reading on both sides to see if it is loading down.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Thanks for the reply, atd ~

Can you tell me what you mean by "check the dc reading on both sides"?

Do you mean, with the voltage applied, I should put the DMM on either the 200 or 600 DC setting and try to read that same resistor for voltage? If so, what does "both sides" mean and what reading should I be looking for if it's indeed functioning okay.