LG 50PG20 - No picture, has sound. Pictures included

[Turco Chips]

Hello all,

I just want a nudge in the right direction / some sound advice.

Typical LG 50PG20 issue of no picture/sound fine. I had a guy come buy from some repair company and quoted me 560.00 which seemed a bit much considering he didn't give me a definite cause. He did want to replace the Z and Y SUS.

Is there a way for me to troubleshoot? I have a multimeter but need some help on where to begin.

Not sure if these pics help or not. A couple didn't look as good as I thought they were prior to uploading from the camera. Please let me know if I need to post some more.

Thanks so much guys!!

[Turco Chips]

Re: LG 50PG20 - No picture, has sound. Pictures included

pics continued....


















Thanks so much for your time folks!!

[tom66]

Re: LG 50PG20 - No picture, has sound. Pictures included

Do you have a digital multimeter? (Not just an analog one.)

* If you have no picture, it's the Y sustain.

* If you have a picture, but it's very poor and washed out, the Z-sustain is faulty. OR, if you have a very dimly lit screen when in a dark room, then the Z-sustain is faulty.

So in your case it's most likely a Y-sustain issue.

Very rarely do both fail at the same time. $560 is completely ridiculous, given a new TV of similar spec is around $700. No wonder more and more new TVs end up in landfill.

The Y-sustain is on the left hand side of the TV looking from the back; the Z-sustain is on the opposite side. The Y-sustain connects to the Y buffers (which connect to the screen), and the Z-sustain connects straight to the screen.

There's definitely one fuse on the Y-sustain that I can see.

You can test this fuse by using the ohms mode on your multimeter.

Check your multimeter is working first by touching both probes together. You should get a reading of less than 2 ohms. (Don't confuse a right hand "1" with 1.0 ohms.)

Then put both probes on the fuse (with the TV unplugged); it should measure less than 2 ohms on the 200 ohm range.

A common fault is for the fuse on the Y-sustain to blow. Most often it blows when one of the IPMs on the Y-sustain fail. These IPMs can be difficult to replace, but the board will certainly cost less than $560!! And it will take less than a half-hour to replace it.

If the fuse shows as blown, there are companies on the internet who will rebuild the board for less than $100, or you can replace the board as a whole unit.

[Turco Chips]

Re: LG 50PG20 - No picture, has sound. Pictures included

Thanks - Haven't checked the fuse out yet but did do this:

(Since this happened the screen has been completely black)

I pulled the upper buffer board from the YSUS and turned the tv on. I got a reddish/orange mess of a picture on the screen.

I turned it off and then replaced the upper buffer board and pulled the lower buffer board from the YSUS. Turned the TV on.....Nothin....black screen. Could it just be one of the buffer boards?

[tom66]

Re: LG 50PG20 - No picture, has sound. Pictures included

Thanks - Haven't checked the fuse out yet but did do this:

(Since this happened the screen has been completely black)

I pulled the upper buffer board from the YSUS and turned the tv on. I got a reddish/orange mess of a picture on the screen.

I turned it off and then replaced the upper buffer board and pulled the lower buffer board from the YSUS. Turned the TV on.....Nothin....black screen. Could it just be one of the buffer boards?

That sounds more likely. The boards are synchronised so if one is missing the other will go a bit crazy but the fact that the screen lit up proves that both the remaining buffer and the Y/Z-sustains are working. Do you have a part # for the faulty one? (usually written on the board.)

[Turco Chips]

Re: LG 50PG20 - No picture, has sound. Pictures included

Well, that's where I'm a little confused. I took the top one out and got the weird picture on the top half of the screen...the bottom half was black. When I reversed that no picture what so ever..... so I'm guessing the upper buffer is bad (??) I should probably just replace both....

Upper - EBR50039007

Lower - EBR50039107

[PlainBill]

Re: LG 50PG20 - No picture, has sound. Pictures included

Well, that's where I'm a little confused. I took the top one out and got the weird picture on the top half of the screen...the bottom half was black. When I reversed that no picture what so ever..... so I'm guessing the upper buffer is bad (??) I should probably just replace both....

Upper - EBR50039007

Lower - EBR50039107

Those are good numbers. The problem would be finding them. I find prices of anywhere from $60 to over $100. There are a pair listed on eBay at $89 each.

The bottom board is defective, the top one is probably good.

PlainBill

[Turco Chips]

Re: LG 50PG20 - No picture, has sound. Pictures included

Thanks!

a couple of questions PlainBill...

Could there be an issue with the YSUS? I mean could there me an issue with it to have caused the bottom board to go bad? Is there a way to check the YSUS for issues?

Thanks so much in advance!




TC

[tom66]

Re: LG 50PG20 - No picture, has sound. Pictures included

Thanks!

a couple of questions PlainBill...

Could there be an issue with the YSUS? I mean could there me an issue with it to have caused the bottom board to go bad? Is there a way to check the YSUS for issues?

Thanks so much in advance!




TC

If the remaining board is still okay, i.e. not smoking/burning, the Y-sustain is probably okay. Most further checks will require an oscilloscope, unfortunately.

[Turco Chips]

Re: LG 50PG20 - No picture, has sound. Pictures included

Ah...thanks! I searched a site for the boards and found that it suggested this as a replacement:

EBR50039101

...nevermind - they're in china and i ain't doing that.

[Turco Chips]

Re: LG 50PG20 - No picture, has sound. Pictures included

OK - I'm searching for the lower board. I ran across this one site - shopjimmy - anyone ever use it? Anyway, When I search for EBR50039107, it shows not in stock, but says "these tv parts also work:" and lists EBR50039105. I DID find that part # at digital city electronics for 50 bucks though. It lists a different board # - is this type of replacement part scenario common?

Thanks again for any and all comments!!

[kcraptor82]

Re: LG 50PG20 - No picture, has sound. Pictures included

Just recently picked up one of these LG 50PG20 units and it seemed to work great until just the other day. The TV still works fine, picture looks great, and audio sounds fine, but one little annoying problem. The video will blink on and off sometimes. It just randomly just goes black and then comes back on. When it does it, it seems to do it within a split second. The TV can play fine for 30 minutes or so, and then start blinking the picture, etc. What could cause this? I have never seen one do this before. There is no set time when it does it. Just at random.

[tom66]

Re: LG 50PG20 - No picture, has sound. Pictures included

Just recently picked up one of these LG 50PG20 units and it seemed to work great until just the other day. The TV still works fine, picture looks great, and audio sounds fine, but one little annoying problem. The video will blink on and off sometimes. It just randomly just goes black and then comes back on. When it does it, it seems to do it within a split second. The TV can play fine for 30 minutes or so, and then start blinking the picture, etc. What could cause this? I have never seen one do this before. There is no set time when it does it. Just at random.

Sounds like a cold solder joint.

[Unspun01]

Re: LG 50PG20 - No picture, has sound. Pictures included

The bottom board is defective, the top one is probably good.

PlainBill

PlainBill:

How did you come to this conclusion?

I was reading this forum, and felt the need to share my experience and ask some questions...

I have a LG 50PG20 Plasma with sound but no picture.

On this TV, the Y-sustain is connected to the upper and lower y buffers, and each buffer is connected to the other buffer with a 5-wire jumper...

Condition 1)
Buffer jumper connected. Upper buffer IS connected to y-sustain, lower buffer IS NOT connected to y-sustain,

No image on any part of the screen.

Condition 2)
Buffer jumper connected. Upper buffer IS NOT connected to y-sustain, lower buffer IS connected to y-sustain,

Lower half of screen displays a darkish greay. Almost like the pixels in the lower half of the screen are on, but not displaying anything.

These tests lead me to believe that the upper y-buffer is bad, which makes sense since this is where the heat would accumulate in these TVs...

One further test I did, is that I had a bad upper y-buffer board from the trash of my local TV repair shop. I removed each of the 4 IC chips from the board and installed the bare board into my TV so the "empty" upper y-buffer, and the lower y-buffer board are both connected to the y-sustain...When turned on, the TV displays colored garbage on the lower half of the screen and has sound. I expected the image to work properly on the bottom with no shorted IC on the upper y-buffer to cause problems...

Does my TV have a bad upper y-buffer or is my lower y-buffer bad ? This seems to contradict what Turco chips has said his TV does when he exchanges which y-buffer is connected.

Thanks.

[electronicsurplus]

Re: LG 50PG20 - No picture, has sound. Pictures included

These buffers are available at shopjimmy see: http://www.shopjimmy.com/lg-ebr38374702-ydrvtp.htm

But, i would first test the Output high voltage Ceramic Capacitors (The orange caps) and, the Output transistors which are mounted to the heatsink for shorts. The YSUS boards are notorious for cold solder joints and connections and, High ESR or shorted Capacitors. You might want to check these before buying a YSUS or buffers.

We have repaired many plasma televisions this way.

You can also visit Coppell tv in Texas, Bobby has a ton of experience dealing with LG plasma and, can rebuild the YSUS and buffers, if needed.

We do not have either in stock currently

Jon

Electronic Surplus

[rmartell]

Re: LG 50PG20 - No picture, has sound. Pictures included

LG 50PG20, MFG 2008 shutting down while watching the other day, does turn back on for a minute then back off, Button is red, standby mode guessing. Any suggestions on how to proceed? I have basic ele skills will this need to go to the repair shop?

[squiza70]

Re: LG 50PG20 - No picture, has sound. Pictures included

Hi guys.Brand newbie novice tinkering with an LG pdp50H20000 i rescued from the side o the road.The picture was perfect except for the far left h/side of the screen.So i decided to try reseat the ribbon cables,but i did so with the power on(stupid ,i know) and consequently lost the whole screen??????????Could it just be a fuse on the YSUS or have i cooked this goose?Also the prob on l/hand side of screen was,the picture was there but blurry n oscillating.Any help appreciated.taa in advance squiza70

[Hamie]

Re: LG 50PG20 - No picture, has sound. Pictures included

Hi guys.Brand newbie novice tinkering with an LG pdp50H20000 i rescued from the side o the road.The picture was perfect except for the far left h/side of the screen.So i decided to try reseat the ribbon cables,but i did so with the power on(stupid ,i know) and consequently lost the whole screen??????????Could it just be a fuse on the YSUS or have i cooked this goose?Also the prob on l/hand side of screen was,the picture was there but blurry n oscillating.Any help appreciated.taa in advance squiza70

When you say ribbon cables, I take it you mean the ones at the bottom of the plasma panel, covered by the metal shield?

If you run the TV without the metal shield in place the ribbon ICs burn up and the panel is toast.

If it's any consolation, by your description, the panel was probably damaged anyway and wouldn't have been fixable.

[Wdurey]

Re: LG 50PG20 - No picture, has sound. Pictures included

I have the same problem as Turbo Chips. I've disconnected and turned on the TV with either y buffer disconnected. Neither made a difference. I have correct voltages to VA and VS. The y sustain board is humming and fuse is good. Not sure what else to do to diagnose.... any ideas???

[Hamie]

Re: LG 50PG20 - No picture, has sound. Pictures included

You'll notice 2 resistors close to where the y-sustain connects to the buffers marked -VY and VSC

Measure the voltage ACROSS these resistors and post your results.