LG Plasma (PDP50R10101) No picture No sound

[SluggerB]

This is my first Craigslist freebie fix attempt. 50 inch LG Plasma TV Previous owner said over time it was struggling to turn on, it would take 4-5 times to turn on, the one day it just did entirely. I took it home and plugged it in, I her a click, then a second later another click, and nothing. Dead as a doorknob

So I took the back off and check voltages. The power supply appears fine, I checked the VS, VA, and 5V voltages and they all measured correct, on the power supply board and on the display boards (Y and X boards). All the fuses are fine

Following a YouTube videos advice, I checked out the board with the connections on it (HDMI, RF, etc) and disconnected the wire running from the power supply to that board labels "M-On". Tried to turn on the TV, and this time actually got the red LED power light to come on. Still no display, no backlight, and no sound.

I took that board out, and nothing looked bad about it, I reflowed the connections just for fun, no change.

Another YouTube video told me to check the Mosfets on the Y and X board for shorts to ground, I tested them, and a couple were continuous to ground, but not as many as the video, and I'm not sure if they are supposed to be or not.

At this point turning the TV on brings on the red light, no display, no sound, and if I press a button (I've been pressing the input button) it does nothing, then I head a click, and it turns off.


The Y Board has a label that reads EBR62294102 and the X Board says EBR62294202
Any thoughts on how to proceed?

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

50pk series, mainboard main chip problem.

if you disconnect the mainboard from the power supply the panel should come on with a black screen as soon as AC is plugged.
and to be completely sure a logic board self-test that displays patterns can be run.

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

50pk series, mainboard main chip problem.

if you disconnect the mainboard from the power supply the panel should come on with a black screen as soon as AC is plugged.
and to be completely sure a logic board self-test that displays patterns can be run.

By main board you mean the board with the inputs on it? If I disconnect that and plug the TV in, nothing happens. The screen does not turn on.

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

yes, main board = inputs, when the mainboard is disconnected, does the power supply relay click and vs/va come on? does the logic board LED blink?
logic board is in the middle of the tv connected to the SUS boards and main board(lvds)

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

With the main board disconnected, and TV plugged in, the voltages are present and correct for VA, VS, and 5v lines, the 17v and 5v lines at the connector that goes to the main board are also present. I get one click from the power supply but no LED and no backlight or any sign of life.

I do not see an LEDs light up although I'm not sure this logic board has one I will need to take a closer look

One thing I noticed last night was I had everything hooked up, turned tv on, then I heard that second click from the PS, and my voltages were gone, and the LED would no longer light up when remote on button was pressed. Pulling plug and reinserting got my voltages back

Also the heatsink on the chip on the main board was slipping off, it was held on by a pad and had slid about 20% of the way off the chip, so I thought that might have lead to an overheating issue. I took the heatsink completely off and the chip appears fine, nothing looks burned

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

I just checked the board in the middle does have an LED but it has never lit up. It lights up on diode mode on my meter so it works but board never turned it on

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

There are other voltages to measure, VY and VSC(Y-SUS), and ZBIAS(Z-SUS).
Find their test points and if they are matching the panel sticker.

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

There are other voltages to measure, VY and VSC(Y-SUS), and ZBIAS(Z-SUS).
Find their test points and if they are matching the panel sticker.

I don't see those listed on the sticker. Which board would they be on?

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

they are listed but not labeled
For example on this photo:
-193 is -VY
143 is VSC
90 is Z-Bias

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

they are listed but not labeled
For example on this photo:
-193 is -VY
143 is VSC
90 is Z-Bias

Where would the test points for those voltages be?

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

they are on the boards, usually across one resistor, look for them.

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

they are on the boards, usually across one resistor, look for them.

I poked around and found the voltages on the smaller middle board. So that board IS getting power, and it appears to be the correct power, but it isn't turning on (the LED is not lighting up, and I know the LED is fine I can make it light up with my meter)

I double checked all the voltages on the power board and the Y and X boards, they all look good. At this point the only thing that seems to be misbehaving is that main board. I tried re flowing the BGA chip, didn't help.

With that board removed, plugging in the TV results in nothing, but I get a single click from the power supply. With that board plugged in, I get the red LED on the front of the TV, but 2 clicks from the power supply, which to me indicates a short on that board somewhere causing the TV to turn off.

I checked everything I could and found no shorts on that board, but the main chip is BGA so I have no way to test that. Think it;s worth replacing it? I can get one on eBay for $40

[R_J]

Re: LG Plasma (PDP50R10101) No picture No sound

If you want to check the panel, disconnect the lvds cable between the main board and the control board, then short the two auto_gen points on the control board and plug in the tv.
What is the TV's model number?
If the led (D1) on the control board is not blinking, the board is not functioning, this may be due to missing voltage to it.

here is a similar thread https://www.badcaps.net/forum/showthread.php?t=67417

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

If you want to check the panel, disconnect the lvds cable between the main board and the control board, then short the two auto_gen points on the control board and plug in the tv.
What is the TV's model number?

Well the main board (one with the inputs) is out of the TV, so it's disconnected.

The control board is the smaller board in the center, correct? Where are those auto_gen points?

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

What is the TV's model number?

LG 50PK550

If the led (D1) on the control board is not blinking, the board is not functioning, this may be due to missing voltage to it.

That board has no direct connection to the power board, where does it's power come from? It has voltages present with the main board removed from the TV

[R_J]

Re: LG Plasma (PDP50R10101) No picture No sound

LG 50PK550



That board has no direct connection to the power board, where does it's power come from? It has voltages present with the main board removed from the TV

Auto_gen points are at R51 & R52, next to C76, lower right hand corner

I believe the ctrl board gets +17v from the power supply via P2 and M5v via the y-sus board to P1 (fl1 & fl2)
The link I posted in #13 has a training manual and a service manual

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

Auto_gen points are at R51 & R52, next to C76, lower right hand corner

I believe the ctrl board gets +17v from the power supply via P2 and M5v via the y-sus board to P1 (fl1 & fl2)
The link I posted in #13 has a training manual and a service manual

Just to make sure we are speaking the same language:

Main board: The bard with the inputs (HDMI, composite, etc)

Control board: The small board in the center of the back of the TV.

The main board gets 17V from the power board, and that voltage is intact. That board does not have an LED on it at all (that I can find)

The Control board has an LED, but does not light up. It has voltages I measured at the various capacitors that seem correct

Other badcaps posts seem to indicate that if the LED does not light up that the control board is the issue and the posters replaced it and it fixed their problem. Are these board interchangeable as long as the part number of the board is the same? eBay has some for $20 that have matching part numbers but are for different models of LG TV's

[R_J]

Re: LG Plasma (PDP50R10101) No picture No sound

Here is a control board, the part number is on the white sticker EBRxxxxxxxx
The voltages are listed in the training manual, I believe you should have 17 volts on FL1 or FL2, I think this voltage originates from the Y-sus board and not the power supply but I can't remember exactly
The EAXxxxxxxxx number is the bare board number only

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

Here is a control board, the part number is on the white sticker EBRxxxxxxxx
The voltages are listed in the training manual, I believe you should have 17 volts on FL1 or FL2, I think this voltage originates from the Y-sus board and not the power supply but I can't remember exactly
The EAXxxxxxxxx number is the bare board number only

It would be the Y board, there is no direct connection between the control board and the Power board. I will test both F1 and F2 for voltages, I believe you are correct that it should be 17V

Just to confirm, as long as the part number on the white sticker matches, a replacement control board will work even if it is from a different model LG? These boards are on eBay for like $20 so I wouldn't mind taking a $20 flyer on it if I can't fix this one.

If those voltages aren't there, and I find that one or both of those caps are bad, do we know the ratings on those? I have a bunch of SMD caps but don't know which to try.

Thanks for help!

Edit: Looking at the manual it looks like those aren't caps but EMI filters. Al tough the manual tells me where to check for voltages so I will go probing around. If the board is getting voltage from the Y board I will replace the control board

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

Checked voltages, and there were present, but the board failed the Diode check, the manual said the diode readings should be 1.3 on the top 4 pins, and all 4 measurements were different and none were near 1.3

Pulled the board and and found one on eBay for 19.99 and free shipping, so I ordered it. Lets see if it works!