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

[Wdurey]

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

VY - 47.3 K ohms
VSC 32 K ohms

[Wdurey]

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

Vsc 13.32 v dc
vy 60.2 v dc

[Hamie]

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

Now measure them again with the buffers unplugged from the ysustain.

[Wdurey]

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

Both are zero... I'm hoping that is good...

[Hamie]

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

Ok so just to be sure you are measuring them ACROSS the resistors?
Black probe to one leg of the resistor, red prove to the other?

[Hamie]

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

If you are, then you have a faulty y-sustain.

[Wdurey]

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

Yep 100% am. Is there a possibility the buffers are good?

[Hamie]

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

Watch this video, it's the same tv as yours and shows you how to test the buffers.

https://m.youtube.com/watch?v=Z9pGXQcxaIM

If they test good then it's just the y-sustain causing your problem.

[Hamie]

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

Also depending on the model sometimes the -vy and vsc voltages will only appear for a few seconds then drop back to 0 with the buffers unplugged.

So make sure you test them quickly as soon as you power on the tv

[Wdurey]

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

I watched the video yesterday. It is very helpful. Unfortunately the buffers are different from mine. The pigtail going from the upper to lower buffer is not there. They use a 3rd connector on the ysus board that both boards plug into. I checked the buffers over pretty well, and nothing seemed amiss.

I will verify the voltages with the buffers unplugged tonight.

If they do not show signs of life I will order the sus board if so what is the next step?

[Hamie]

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

Upload a picture of your buffers and we can point out the floating ground etc.

If you definitely are getting no vsc and -vy your y-sus is faulty.
Vsc should be roughly 150v
Vy should be roughy -180v

[Wdurey]

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

Will do when I get home tonight. Mondays are annoying.

Thank you so much for taking time to help me out!!!

[Wdurey]

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

Got maybe 10 volts out of the VSC. VY maybe 40 volts. This was somewhat of a spike then fall.

The pictures:
I have gone from common ground to all pins going to the screen with no shorts on either. Each of the four pads on the rear to the pins headed out to the screen. Also, common ground to common ground using large bad and the lower pad.

[Hamie]

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

If there are no shorts in the buffers they should be good.

Replacing/repairing the y-sus should resolve your fault.

[hondaleblanc]

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

could some post a pic of what the y sus looks like , thanks inadvance ...new to this site

[Lloyd6202]

I realize this is an old thread but maybe i can get some advise plz

[dick_barton]

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

I realize this is an old thread but maybe i can get some advise plz

It's an old thread but you have not said what your problem is or what if any measurements/ testing you have taken/done. Have you read the complete post and carried out the checks suggested in the thread and what results did you have. Is your set the identical model and are the circuit boards identical to the photo's at the start of the thread?

[Lloyd6202]

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

Yes i have read for weeks and now replaced the power supply, y sus board and the z sus board.. I have brought it back to life from nothing now i have the top half and a square of static that alternates back and forth..so then i knew i would have to replace the buffer boards..i found one finally the bottom one..waiting for that and see what happens

[pulper111]

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

Like Lloyd6202, I realize this is an old thread but I am having a problem with two LG 50 inch plasma TVs and am hoping someone can help. Let me know if you think I should start a new thread.

Both have the same power and Y-Sus boards (same part number and numbers on the white stickers). Power boards are fine. However, after some troubleshooting I have found that the Y-Sus boards seem to be the problem. The Y-Sus boards are EAX64282201/EBR73763201. I've tested the resistors using a DMM and replaced one on one of the boards. However, both boards have faulty ceramic capacitors in the exact same locations. I've read that ceramic capacitors rarely go bad, so I'm wondering about this. I have checked them using the MESR-100 ESR Meter and they show up as overflow. The faulty ones are 4 disc shape ceramic capacitors and one blue radial style capacitor. Here is a link to a picture of this board.

http://kazpol.com/img/products/62/72/1_max.jpg

The 4 disc shaped capacitors are (in the picture) near the left side just above the black heat sink, and the blue radial style is in the middle of the board again just above the black heat sink.

The symptoms of one TV is that it will turn off 1 second after turning it on. The symptom of the 2nd TV is that it will turn on, there is humming coming from the Y-Sus board, and a faint clicking sound near the top of the board (what would be the left side in the linked pic). It will stay on but there is no picture.

Does this sound plausible that this many ceramic capacitors have gone bad? I am new to trying to fix things/troubleshooting so please forgive any errors in terminology that I've used. Thank you.

[Quietwind]

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

If you definitely are getting no vsc and -vy your y-sus is faulty.
Vsc should be roughly 150v
Vy should be roughy -180v

First Off, Thanks to Hamie for the reference specs and the test procedure!

Detail:
Model - 50PG10-UA YSUS BRD #EBR50038901
Symptom- Power on, No video/picture, sound normal .... Initially the video would come on for the first 20 seconds or so, then BLACKOUT occurred. Unplugged a minute or two then restored power, and attempt power on again and picture would be restored briefly. After five attempted resets; video no longer turned on, (power input remains on/ steady black screen).

YDRV Buffers removed tested normal, tested for shorts, grounds no visible damage!

Reference voltage specs Vsc, Vy. I'm really suspecting YSUS board is done but puzzled because along the lines of Vsc/Vy the voltages I received when tested with "Buffers removed.... I noted this model seems to be of the variant that the voltage voltage reference drops off once power is switched on

1) I'm trying to figure out if there is a relevant adjustment spec for VSC , and VY because this YSUS board has two trimmer pots just below VSC resistor; thinking I could then possibly regulate or adjust voltage while reading voltage across resistors but problem I don't know the data spec voltages specifically and they are not shown on Panel like VS , VA.

2)Maybe someone can help as I'm pretty certain YSUS board has failed but I will have to retest with buffers attached and try and get voltage reference at VSC,VY resistors again. Buffers "removed", VY seemed to spike at 240v, VSC seemed approximately 160v before they both dropped off within a couple seconds to nearly nothing almost instantly.

Reinstalled YDRV buffers, repeat voltage test connected in parallel, across resistors. Same VY, VSC voltage readings taken across resistors peak at about 50% previous readings but drop off to zero but would think this would occur with the load from the driver/panel circuit though power remains active from PS input socket. (LED)@LOGIC CTRL. =GREEN/ACTIVE reammains on steady, "Power On" which seems okay. Main Logic has two LED'S; one seemingly STDBY. turns red power off, seems primarily green to amber steady while power is on

"Input" voltages from PwrSupply at YSus socket all test correct voltage remaining constant while powered "on" VS@194V, VA@60V, 5v.

Other Note: (LED)@LOGIC CTRL. =GREEN/ACTIVE remains on steady, "Power On" which seems okay. MAIN LOGIC has two LED'S; one seemingly STDBY. turns red power off, seems primarily greenish/amber steady while power is on, and another LED near video output sockets "momentarily turns green when powering on then goes out after a couple blinks but stays on steady when you expect the video picture to appear. Main Logic has also has reset button on board.... push the reset and it power cycles the tv but still no video image. Sound normal playing blue ray HDMI. It also might seem possible main logic has expired.....

3) If anyone has a line on service E-manual for LG 50PG10-UA that would be greatly appreciated! schematics.... would be freakin awesome!

4)Lastly if anyone has an idea how to remove the nasty thermal pad tape without destroying it to further test and specifically inspecting solder joints on the board underside..... I kinda think with the need for thermal pad tape beyond the heat sinks the thermal tape is likely hiding my problem source.