Lg 60PA5500 No picture

[WeadroW]

Re: Lg 60PA5500 No picture

Ysus board 2 voltage readings from top connector to bottom.

With buffers connected. | without buffers
Pins 1-6 2 volts. | Pins 1-6 no voltage
Pins 7-12 jumps 11v to1.8v | Pins 7-12 92v
Next 12 pins 2v. | Next 12 pins 92v
connector #3 jump 9v-11v | Next 1-4 95v the rest jumping unsteady

Connector 4 near VSC was unstable with no buffers connected jumping from 8v to 3.8v. No steady voltages on this connector with or without buffers. Clearly there is a voltage issue with VSC being generated on this board.

Connector #5 jump 1v to 9v | All pins 95v steady
Connector #6 steady voltages with and without buffers similar to my original post above.
All z sus voltages were steady, output was 76v without y buffers and 79v with y buffers connected. VZB steady 119v. Here is a photo of the front of the z board.

I checked all the axial diodes and they appeared good. Only odd readings I had was D506 .42 and reversed .859, this was in circuit same on both boards. Also, D256 was reading 0 both directions in circuit on both boards. I can take this one out and test if needed, it was located top left near the large white resistor.
I did leave the buffers connected to the ribbons but not the y board, is this considered completely out of circuit? I will switch the y board and test that one tonight in similar fashion. Thanks

[WeadroW]

Re: Lg 60PA5500 No picture

Ok, so I tested ysus 1, and I did not get much for voltage at all. This is with buffer boards disconnected. I turned the TV on, and for the first 30 seconds I was able to get 177v on connector 1 top 4 pins, but as I continued, I wasn't getting any voltage on any of the connectors besides connector #6 on the bottom. Vy voltage was steady at 196v, and the outputs from the z board were 76v steady.
This did make me wonder if my logic control board is shutting down the y sus? Is this possible? I disconnected the ribbon from the logic to ysus, and checked voltage but did not get any voltage on the connectors. I am getting the same 4 blinks on the logic board. I tried to power cycle the TV several times to duplicate those original voltage readings, but I could not get voltage on the connectors. I didn't even attempt to diagnose with buffers connected since I can't even get voltage with them disconnected. VSC voltage was not present again. Here is a close up picture of the ysus board.

[Nick's Tvs]

Re: Lg 60PA5500 No picture

In our specific situation I do believe we are fine, however when testing a board out of circuit, you do want to have it completely disconnected from the tv. If you don't, depending on the set, you could get a bad reading and also could damage your ribbons by putting unnecessary pressure from the buffer.
Just to make sure we are checking this as well, but the VS voltage I assume is always good and never fluctuates correct?

Here is what I would like you to try. With your Y2 plugged in, and the buffers connected in circuit, remove your Z-sustain from circuit and check the voltages between Y and buffers. just check for fluctuation. In some models the Z will cause these issues. If you are still getting fluctuation, remove the ribbon from the logic to the y and check again. Finally if you are still getting fluctuation after that remove the buffers. At this point if you still see the fluctuation we know for sure that the second Y that was sent to you was either not in fully proper working condition, or your tv caused it to go out and we might need to replace both sustains at that point.

[WeadroW]

Re: Lg 60PA5500 No picture

Thanks for the suggestion Nick. So I did remove the Zsus completely from circuit (including ribbon to control board) and the ysus was still ossilating just as before. (With y2 connected) When I disconnect the ribbon from control board to ysus, the board does not generate any voltage to VSC or vy.
Yes, my VA and VS have been very solid during all these tests.
I noticed this same occurrence on ysus1 when I unplugged the ribbon to the control board.
Is this starting to point at the control board or should the y boards be generating the voltages without the control board connected?
I have not tested with buffers removed yet. Will report back soon.

[WeadroW]

Re: Lg 60PA5500 No picture

With the z sus disconnected.
I am getting steady voltages with each buffer connected 1 at a time. I do not get any (+) VSC voltage, but I do get a reading on the (-) side of the test point of 91v. The pin outs on the connectors hold steady at 93v. Vy is steady at 93v. I connected the buffers again and disconnected the logic board. I just got a click on and click off. With the logic connected, I get the same ossilating voltage on the y board. With no buffers connected at all, I'm not getting and VSC voltage.
I'm going to attempt to reconnect the z again and do 1 buffer at a time with each y sus board to see if I have bad buffers or need a new ysus. I am still skeptical of the logic board functioning correctly.

[WeadroW]

Re: Lg 60PA5500 No picture

Update:
I decided to probe around on the control board just to see if I was getting shorts or anything odd. Photo of the control board is attached. Right off the bat, I was getting shorted readings across C458 and C406. IC253 was also reading shorted across the large pin on the left, the middle leg and the bottom leg. Is this a normal occurrence? I also checked from ground to both sides of the caps and the ic and it read short.
So this is my current situation. I reconnected the z sustain and removed the top buffer board. The set primed with the bottom 1/2 of the panel. I then decided to jumper for the test pattern, and disconnected the lvds. I did get the test pattern to appear on the bottom 1/2 of the screen. It looked like shit. The solid colors were grainy, the whites were kinda pixelated, and the bars moving across the screen had a multicolored background during that phase. I did notice the very bottom section (2in) seemed a little worse then the rest of the panel.

Is this any indication of a bad control board?
I am getting about 91v steady to VSC, and steady vy voltage with just the bottom buffer attached.

[Nick's Tvs]

Re: Lg 60PA5500 No picture

Some of those caps are supposed to read one of there legs shorted to ground. That's normal. As for the IC having a short that's also probably normal, but I couldn't tell you which leg is supposed to have what readings. If your set primed and you were also able to get the test pattern to appear, it sounds like a good logic to me. I don't know to much about the specifics of logics but I have not had a logic cause the color issue that you are experiencing, usually that's from a bad Y or bad Z, sometimes both.
To be totally honest, I don't think I can help you very much without being in front of the set myself.
What I can tell you is that if you can get image to appear only on the bottom half, its probably due to a bad upper buffer. Did you not say you had already replaced it? If you replace that upper buffer, you will however still have a bad grainy picture more than likely, and in my opinion will be due to a bad Z would be my guess. How to test that and make sure what I am saying is 100%? I couldn't tell you, but that's probably what I would do from experience at this point. You said you did double check the solder joints on the Z-sus correct? Bad/cracked solder joints can cause discoloration in picture, and damage on other components.

Anyone have any idea exactly where to go from here?

[WeadroW]

Re: Lg 60PA5500 No picture

Nick,
I really appreciate the insight you have provided. I do have a different issue I just came across.

I connected everything back up except connecting the upper buffer to the y sustain. I did connect it to the panel and the lower buffer. I ran the test pattern. I got the entire screen to illuminate basically the way it showed in my original posting. I did see a problem though. I have a 3" verticle strip that is not functioning. The 3" strip next to it is also projecting different colors then the rest of the screen. Am I looking at a possible bad ribbon connection possibly on one of the lower buffers (XC, XR, or XL). I will tear into the bottom of the set and report back. Is it possible this strip had been causing my headache with the rest of the set?
Thanks again

[Nick's Tvs]

Re: Lg 60PA5500 No picture

Did you end up figuring out the issue?

[WeadroW]

Re: Lg 60PA5500 No picture

I'm awaiting on the arrival of a new y sustain board. It seemed to be the common issue not generating the VSC voltage. My fear now is that I still will end up with this vertical bar on the screen. I will post updates as soon as anything changes.

[Nick's Tvs]

Re: Lg 60PA5500 No picture

Sounds good. Good luck!

[WeadroW]

Re: Lg 60PA5500 No picture

Well no luck. The new y sustain board is giving the same symptoms as the other 2 I have. I ordered a new control board because that is the only other board that plugs into the y sustain besides the panel when it is doing this behavior. My next move would be z sustain, but that would be a stab in the dark.
-I'm not understanding why top and bottom buffers work on their own, but when both are connected I get nothing?
-I have yet to get any image on the screen, just colors, that is why I'm attempting the control board. Anyone had similar experiences with this 60" model? I'll keep updating. Thanks

[WeadroW]

Re: Lg 60PA5500 No picture

Biting the bullet on this one and throwing in the towel. The new control board made no difference. Symptoms have remained the same throughout all this board swapping. I'm afraid even if I did finally figure this out, I will have a vertical bar on the screen. I feel ok letting this go finally because I have been able to fix 3 other plasmas during this particular TVs struggle. On to the next one... Just thought I would conclude this post.