Lg 50pz550

[tom66]

Re: Lg 50pz550

This is a chained energy recovery set, and both boards may need simultaneous replacement. One board can kill the other. Like the thin Samsung plasmas.

[migimara]

Re: Lg 50pz550

Hi Tom thanks for the input. By chained recovery energy, do you mean since the z sus connects directly to the y sus that one or the other may be fried out? Now why would that happen? What's causing it to spark?

On a side note, after the z sus sparked I disconnected it from the y board and after a few minutes attempted to turn on the TV. For maybe 2-3 seconds it powered on without the z sus and noticed the led on the logic control board turned green then everything went off and now having the repeated symptoms.

I did notice though.. The z sus board I ordered was a bit different from the original one that came with the TV. And I think in comparison was missing a component. Could that have caused the 2nd spark? I'd like to think the 3 y sus boards that I bought are still good...

[Ltank]

Re: Lg 50pz550

Use your meter on ohms. Check Y and Z board. Place meter leads across the gnd and power pins on each of the boards. One of the two or both should show a short to gnd.
Once the short is located, you can replace it or repair it. Hope this helps.

[tom66]

Re: Lg 50pz550

Older plasmas had two energy recovery circuits, one on each board. Energy recovery makes lighting the plasma screen more efficient. Really old plasmas had a third circuit for the address drivers but that's not used any more. The newer plasmas like this one have moved to a chained ERC (energy recovery circuit) which the Y-sus and Z-sus share. If a failure on the Y-sus occurs, it's possible for the Z-sus to be damaged at the same time. Therefore, when replacing boards on chained ERC plasmas, it's recommended to replace both simultaneously from known good sources.

[Ltank]

Re: Lg 50pz550

What I meant was there should not be a short across the pins. You should see a resistance of several thousand ohms. A short would be a much lower like 10 ohms or less
Sorry for any confusion

[tom66]

Re: Lg 50pz550

I was replying to migimara, what you said is sensible and should also be tested.

[migimara]

Re: Lg 50pz550

Alright I'll test the boards when I get home. What I'm puzzled about is lets say both boards are placed simultaneously, what would it mean if it fails again?

[tom66]

Re: Lg 50pz550

One or both boards are bad, or somehow there is a fault with the control board or panel. The last two are very rare.

[migimara]

Re: Lg 50pz550

Alright I think I've just about had it. Got 2 new y and z sus boards today and it seemed to power on for about a minute but there was no picture or sound so I turned it off. I turned it on again I saw the screen come on with a black thick horizontal line on the top half of the screen then the speakers made a loud growl noise... Then the z sus popped yet again. Took off the back panel unplugged the z board and tempted to turn on the TV again. It turned on for a couple of seconds then the middle black bar thing on the y board sparked at the tip of the black thing. It's getting pricey so what is causing these issues now? Could it be the panel? I'm guessing those are a bit difficult to replace.

[tom66]

Re: Lg 50pz550

Horizontal line from top to bottom? It could be the panel is cracked or damaged, even if just on a corner or in the middle of the screen. Some newer plasma screens will light up when cracked, but can damage the sustain boards when this happens.

Could you perhaps get a picture of what it looks like when it turns off?

Also, try isolating the speakers by disconnecting them to confirm the sound definitely is coming from those.

[migimara]

Re: Lg 50pz550

Hey Tom let's see if I can upload some pics from my phone. Took pics of the back panel off with close ups on the y and z sus boards. On the screen the line was a bit above on the top half of the screen. It went left to right and the thickness was about 2cm and it was also squiggly. If I recall the 2nd time I turned it on when the loud sound happened seems to be coming from the top right part of the screen, where the y buffers are. Is it possible that the y buffers could be causing an issue? or the main board? I do know that if the main board is not plugged in to the PSU board it would just click on then off. If the y sus board is disconnected with only the main board connected it will just turn on without picture.

As for any cracks on the screen I don't think I saw any when the TV turned on briefly since it was backlit when it was on. I only noticed the thick squiggly line.

[marty-clubber]

Re: Lg 50pz550

Hi i have this same Plasma TV powers on but with no picture or sound siuspect main av board have no jumper wires to test av board what else can i use?