LG 60PZ550 Plasma - No Sound, No Picture

[southbound]

Hello,

My LG plasma died out without warning the other night while my daughter was watching it. She wasn't standing very close to it at the time, but said she didn't hear anything unusual.

I can turn it on and the power indicator (front panel) responds, the relay clicks once, but there is no sound or picture. I see no change in the screen at any point (no glow). With the rear cover off and the TV 'on', I see a diode (D1) on the Control board flashing two long, then two short, if that helps any. The Va & Vs test points on the Power board (to chassis ground) both look fine to me {Va:55 = 54.9v , Vs:201 = 201.6v}.

Any advice on where to go from here? I've worked with some electronics in the past, but am new to TV's. I'm sure I can take whatever readings are needed, but might need clarification along the way.

That being said, I have what is probably a silly question regarding checking the fuses on my boards. I am not familiar with the way these fuses are mounted to the board. How do you remove them? I'll attach a picture showing what I am seeing.

Thank you.

[R_J]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Those fuses are soldered into the board, check them with your meter, should be close to 0 ohms

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Ah, they don't make it easy eh?

I checked all fuses I see and each was good.

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

So based on the behavior I am seeing, are there any suggestions on what I should check? Thanks.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Can you post a picture of the Y-sustain and Z-sustain boards?

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Sure. Here are some cell phone pics. If you want more detail, let me know and I'll post clearer ones. Thanks.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

OK, on the Y-sustain, there should be some points or components marked Vsc and -Vy, do you see these? They may look similar to the "Vzb" marking on the Z-sustain in the top right corner.

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

I see them.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

OK, can you measure the voltages across those points?
Multimeter on DC 1000V, red on (+) marked, black on (-) marked.

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

The readings on the Y-sustain look good: Vsc = 150.4v , Vy = -178.3v
{tag calls for 150v & 178v, respectively}

I didn't know if you wanted me to check the Vzb on the Z-sustain board, but I did and when the set powers on it will climb up to ~6v then slowly bleed down.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

It looks like from your Vzb reading the Z-sustain is failed then.

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Thank you for your help, Tom. It looks like we are getting somewhere. My next questions are:

1. Is the Vzb dependent on anything off the Z-sustain board that should be checked?

2. Is this something that can, with a little guidance, be traced further to the component level, or is it more practical to just replace the board?

If a board change is needed, any recommended sources?

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

I've ordered another Z-sus board. I'll report back with the results.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Sorry, I missed your previous post. Hope the swap fixes it. As for causes, I'd be thinking that there's a short on the Z-sustain dragging the Vzb down with it. Possibly the SUS-DN FET/IGBT shorted. Repairable, but will cost at least $20~$30 in parts plus time to diagnose.

[Fletch]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Is there a viable test for LG plasma buffer boards?

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Yes but only if you post in your own thread.

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

I know that when ordering a replacement, I should look to get the same Rev #.

When I was shopping around for a replacement Z-Sustain board, the EAX62076601 rev G boards were going for $50 and up. I came across one at indyoutletcenter.com for only $2, but it didn't show the revision. Since it was less than $10 delivered, I took a chance and ordered it. It just arrived and is Rev H whereas my original is Rev G. Do you think it's safe to try this one or is there a risk of damage and should just order the same rev board?

Thanks.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

Do you notice any substantial layout or connector differences? How about a comparison photo?

[southbound]

Re: LG 60PZ550 Plasma - No Sound, No Picture

No differences that I have picked up. Here are some comparison pics.

[tom66]

Re: LG 60PZ550 Plasma - No Sound, No Picture

That should work fine. If one of the inductors (copper coils) or large capacitors were missing, it might have been for a 42", for example, which would not work well. But it looks identical to me, so it's probably some minor revision like changing a component supplier to reduce costs.