Lg 50pv450

**tom66** · 10-08-2013, 12:32 PM

Re: Lg 50pv450

There is a problem with the Y-sus, control, Y-buffer or Z-sus, in that order, if you see sparklies when powered on but no picture then appears. Voltage/setting adjustment will not help for now. In some cases initial sparkling may be normal if it goes away once set is displaying an image. Do the sparklies go away? It may be normal power up procedure.

Can you supply a picture of the control board (sometimes called logic)? There is a test jumper on most of them which can be activated to see if the new main board is bad, which will cause dark slightly glowing screen with no visible image. In a very dark room do you see any glow from the plasma screen?

**TennesseePaul** · 10-08-2013, 12:47 PM

Re: Lg 50pv450

Hi Tom,

Thank you for the reply. I will work to get the answers for you, but must state before hand that this may take a while. I have a 1 year old in house, so all work must be done in the evenings to avoid frying the little guy.

Q: "Do the sparklies go away?"
A: Yes. When I power on the TV, the screen shows pretty black with scattered sparkles that then disappear after a few moments.

Q: "Can you supply a picture of the control board (sometimes called logic)?"
A: I will work to get that image posted this evening. --EDIT: I am not certain off the top of my head where this would be located. I know the YSUS (upper left), Power Supply (center), ZSUS (upper right) and Main (lower right).

Q: "In a very dark room do you see any glow from the plasma screen?"
A: I am not entirely certain. When I powered it up, there was maybe a glow and sparkles scattered about, but it appeared to go all dark after a few moments. I can see if I can make the room darker to see if it is actually still "glowing" after the initial event. I tend to think not though.

Thanks again for your reply. I really appreciate the help.
--EDIT: I've been working off this manual.

Tennessee Paul

**TennesseePaul** · 10-08-2013, 05:58 PM

Re: Lg 50pv450

Hi Tom,

Attached are the images. I tried to capture the full "boot-up" screen but wasn't fast enough with my camera.

When it first starts up, the entire screen is "sparkled".
Then it is only half the screen. Then it goes dark.
I can tell there is some "light" going on in there. Perhaps a back light. But, even in a dark room, the "glow" you mentioned I wasn't able to see. If there was a plasma glow, then it did not appear. But I could tell there was some sort of light going on there. It looked like a black image vs a turned off set.

Included are also the pictures of the boards and the entire back of the panel.

Tennessee Paul

Attached Files

**tom66** · 10-08-2013, 06:37 PM

Re: Lg 50pv450

To me, it looks like a bad Y-buffer or Y-sus, possibly both.

You can try this test to see what you get. Perform the changes with power off, then plug it in. You should see a sequence of test patterns if it's working, but I suspect you will see nothing more than you currently see. This board is the control board.

Attached Files

**TennesseePaul** · 10-08-2013, 07:26 PM

Re: Lg 50pv450

Hi Tom,

Thank you for the response.
The changes you are talking about are replacing the 2 boards you mentioned?

TennesseePaul

**tom66** · 10-09-2013, 02:40 AM

Re: Lg 50pv450

No, I'm talking about powering it off when following the instructions in the image attached.

**TennesseePaul** · 10-09-2013, 06:43 AM

Re: Lg 50pv450

Hi Tom,

I see now. Thank you for the clarification. I will give that a try tonight.

Tennessee Paul

**TennesseePaul** · 10-11-2013, 09:12 AM

Re: Lg 50pv450

Hi Tom,

Wanted to post an update so as not to disappear. I have been swarmed by other duties lately. I plan on getting to this tomorrow. At that time will have more information on the results.

Thank you,

Tennessee Paul

**TennesseePaul** · 10-12-2013, 11:07 AM

Re: Lg 50pv450

Hi Tom,
I did as instructed. The screen didn't do all that much. It showed some pixels as before but even less briefly. The color was largely red. Then it went dark.

Tennessee Paul

**tom66** · 10-12-2013, 11:42 AM

Re: Lg 50pv450

Can you check your old Y-sustain to see if the picture is any different?

**TennesseePaul** · 10-12-2013, 12:40 PM

Re: Lg 50pv450

The old board hissed high pitch and clicked. With it in the TV will not power on. It cycles attempts, but never succeeds.

**TennesseePaul** · 10-12-2013, 12:47 PM

Re: Lg 50pv450

Out of curiosity, what did the jump do?

**tom66** · 10-12-2013, 12:56 PM

Re: Lg 50pv450

The jumper enables the internal test pattern generator. (The LVDS cable must also be removed to enable it.)

Can you check the -Vy and Vsc voltages on the Y-sustain? They will be labelled. To test, put your meter across the indicated points set to the highest DC range.

**TennesseePaul** · 10-12-2013, 01:15 PM

Re: Lg 50pv450

Interesting. Could I have jumped poorly? I did not solder. I just put a wire end in each.

**tom66** · 10-12-2013, 01:44 PM

Re: Lg 50pv450

If the result is different (you noticed a difference right?), it cannot have been the connection. That is how I would jumper it, just a wire or bent paperclip.

**TennesseePaul** · 10-12-2013, 02:02 PM

Re: Lg 50pv450

Yes. It was different. In a few I will post the results of the meter.

**TennesseePaul** · 10-12-2013, 02:18 PM

Re: Lg 50pv450

Vsc starts off high. Around 178 but falls off to 0.
Vy starts off high, over 200, but falls off quickly and ends at 0.

**tom66** · 10-12-2013, 03:55 PM

Re: Lg 50pv450

OK on the back of the metal backing of the plasma panel (inside the unit) you have a sticker marked e.g. LG Electronics PDP50xxxxxxxxx with voltages like VS: 206V, VA: 58V marked on it. Can you take a picture of this sticker?

**TennesseePaul** · 10-12-2013, 04:50 PM

Re: Lg 50pv450

Hi Tom,

Attached is the picture.

Attached Files

Lg 50pv450

Lg 50pv450

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