LG 50PG25 Plasma black screen problem

[Shadow911]

Hello everyone, first post. Found this site looking to find a fix for my tv. My LG 50" Plasma 50PG25 went black last weekend. Didn't hear any pops or anything just went to turn it on and it wouldnt.

Symptoms: Standby light is light (red) when the power button is pressed. The power light turns blue and flashes 7 times on the seventh time stays solid blue. The panel doesn't light up or anything. I can hear the relay click when i plug it in and press the power button, and when i press the power button to turn it off the relay clicks as well and the light goes back to red indicating its in standby.

So far I have the back of the tv taken off. When I plug power into the tv. The green light on the control board and the green light on the main board light up. I have measure all the outputs from the power supply with a DMM and im getting correct voltages. On inspection of the PS, all caps look great no bulges or leaking. I have the service manual for a 50pg20 which is almost identical to my tv. Checked all fuses on the Z-sus, Y-sus and power supply all good. This includes the ceramic fuses and the surface mount fuses.

On the Y-sus card there is a label for VZB and -VY. When the tv is plugged in i tried measuring across the resistor and i get zero voltage. According to the sticker i should be seeing some high voltage there. I read in another post on here to try unplugging the y-sus and try to turn on the tv, tried still back. Then i tried the opposite without the z-sus plugged in still black. Next I went to the Y-buffer cards they are located on the left hand side and are plugged into the Y-sus card. I removed the top buffer card and I get the bottom of the screen show light there is no picture cause i don't have a video source plugged in but i think this means that the panel might still be good. Next I plugged the top buffer card back in and unplugged the bottom buffer. Stays black. I read that both drivers are synced so if one goes it will affect the other. So I have ordered a new upper buffer card. But im worried that it might actually be the y-sus card because of my voltage readings on it 0v when everything is plugged in. However with the top buffer card unplugged i was getting fluctuating voltages thats why i ordered the top buffer card.

Sorry im kinda long winded. Trying to explain all the stuff i have checked over. If anyone has any suggestions i would appreciate some help or if you think i was correct in ordering a replacement top buffer card that would be great news.

Thanks
Josh

[Shadow911]

Re: LG 50PG25 Plasma black screen problem

Have I offended anyone? Nobody can chime in and possibly lend a hand?

[JimmysTGP]

Re: LG 50PG25 Plasma black screen problem

Have I offended anyone? Nobody can chime in and possibly lend a hand?

Didn't offend me, However came across a 50PG20 with the same issue. But when I place a DMM across Vy & Vsc the Voltage come up then one second later they drop to zero even when I disconnect each buffers. however all voltages are correct coming out of PS. Va & Vs are stable, Screen does Flash when first turned on as well theirs sound so main boards good. LG is telling me replace Ysus and both buffers. Let you know how this works out. Hope this helps.

[awyatt2]

Re: LG 50PG25 Plasma black screen problem

sounds like power supply is in protect mode, you have a short somewhere probally y buffer or y main. i have to leave for work some one proballly will be around in a few minutes, usually the power supply protection kicks in when it finds a shorted board. have the same problem with a hitachi ,been fighting it for a week with no progress

[tom66]

Re: LG 50PG25 Plasma black screen problem

I had the same problem with a 42PC1D turned out to be AC detect - with a multimeter check if AC detect is stable (should be fixed 5V.) (Might be marked ACD or AC-DET on PSU.)

[dcapper]

Re: LG 50PG25 Plasma black screen problem

I have the same tv and finding the same symptoms as the op. 7 blue light blinks then on solid. Audio no video. Green lights on the same boards. All fuses reading good. Ceramic resistors on the psu are reading properly. Any ideas? I unhooked the bottom YDRVBT and I got the top half of the picture working. I also noticed there is a surface mount cap at the bottom of the YDRVBT that looks like a filter to ground is missing C203. Anyone know what that cap size should be?

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

I have the same lg with the same issues, only difference is mine flashes 2 blue, then solid blue no, pic or sound, can some body help with this issue. all voltages check fine. have repair man. was told main logic board bad, if any green leds are lit to replace board. Any help would be greatful, thanks George

[Alastair E]

Re: LG 50PG25 Plasma black screen problem

I have the same lg with the same issues, only difference is mine flashes 2 blue, then solid blue no, pic or sound, can some body help with this issue. all voltages check fine. have repair man. was told main logic board bad, if any green leds are lit to replace board. Any help would be greatful, thanks George

Green LED's on control-board/logic board--are a Temperature Indication, and not a reason to change the board.

How is the -Vy and VZ-bias voltages?

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

I'll check those and get back to you, thanks for the suggestion. George, also I applied my HDMI from cable box and discovered I do have audio, great sound, still no pic. top half of my y-sus is cold, bottom gets warm.

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

Pulled my upper y buffer,and surprise I have half of lower panel, bunch of colored bars,colored snow,ect. did a diode test of board found bad ic's, pulled lower also, same thing. I went to shop Jimmy. com for replacements. Is there still a problem with my y-sus, because, another gentleman in this thread has same tv with exactly, the same symtoms as mine. He sucessfully repaired his problem replacing y buffer, both mine are faulty, any suggestions. All voltages check out fine.

[dcapper]

Re: LG 50PG25 Plasma black screen problem

Both buffers could have blown. Replace both of them and it should work. Have you checked your voltages on your YSUS? Make sure they match the panel.

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

They do, How do you adjust voltages when they do not match panel, on y-sus. I just want to learn how to do things I never attempted befor. Thanks, George

[tom66]

Re: LG 50PG25 Plasma black screen problem

On the back metal plate inside TV where everything is mounted, what's the part number of the panel....? E.g LG PDP50R9#####

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

I want to thank everyone for all the advice on repairing my
LG 50 PG 20.I had a major mishap with one of the ribbon cables from the panel on lower y sus, small tear. I do believe it went into the small copper lines, so I think I'll just part it out. I know there is no repair for this, lesson learned. thanks again all, for all the great help. I would have never fixed it with out all of you! George

[dkneyle]

Re: LG 50PG25 Plasma black screen problem

Sad to think you got close to a final fix. Bit of a reminder for all that those ribbon cables can be very fragile.

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

Yea, I'm a little upset with my self, when I removed the upper y-buffer and got half of the lower screen, I should have left it alone, but I removed the lower y-buffer and my ribbon cable would not release. I wanted to check to see if it was bad and found out after, it was ok. Just a little too late. Now I have some parts, and a screen to dispose of. Tough lesson to learn, but I will move on with another. thanks again for all the info, and Help. George

[rccrasher65]

Re: LG 50PG25 Plasma black screen problem

My repalcement parts came in today, if anyone needs, working boards, just email me at rccrasher65@ yahoo.com If I can help with parts just let me know.