LG Plasma (PDP50R10101) No picture No sound

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

Diodes check on service manual are nonsense most of the time, I had an LG 50 inch plasma tv and the board was fully working but the diode check comparison was way off.

What matters are shorts on switching devices or open resistors.

I think your control board is suspect by not lighting up the led when it's receiving the voltages from Y-SUS.

[nomoresonys]

Re: LG Plasma (PDP50R10101) No picture No sound

I think its the control board too, no heartbeat, seems to be dead.

[R_J]

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!

The 4 pins are connected together so the reading should have been the same, I suspect there was a small charge on the 18v line throwing off the diode reading, the meter uses a small voltage to check resistance and in diode test so if there is even .5 volts on the 18v line the reading will not be as marked in the manual.
I'm not sure how they came up with a diode mode reading of 1.3v I would think it should be close to open.

They did have a problem with those same type filters on some main boards, they were on the data lines and they would become leaky and short the signal going through them to ground.

I had a closer look and the 18 volts is not used by the control board, it just runs through it to feed the Z-sus board.

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

Diodes check on service manual are nonsense most of the time, I had an LG 50 inch plasma tv and the board was fully working but the diode check comparison was way off.

What matters are shorts on switching devices or open resistors.

I think your control board is suspect by not lighting up the led when it's receiving the voltages from Y-SUS.

That was another reason I suspected the control board. The voltages all look correct, and the LED works is I poke it with my meter on diode mode so I know it isn't broken, but it doesn't turn on by itself. Voltages at the caps all measure correctly.

I could have kept poking around, but honestly for $20 for a whole new board it didn't seem a worthwhile use of time to try and find the exact component that went bad

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

Replaced the control board, no dice. Zero change in behavior.

I did notice one thing though: With the main board connected (the one with the inputs), when you plug the TV in, you get 2 clicks from the power board. If you disconnected the main board and plug it in, you get one click.

I am musing that the second click is the power board killing the power because a short on the main board is present, and with the main board out the short is gone so it doesn't turn off.

During all of this the screen is always off and will never come one. Youtube videos seem to point to either a bad main board or bad mosfets on the X or Y board.

[nomoresonys]

Re: LG Plasma (PDP50R10101) No picture No sound

easy enough to test them, one video there: https://www.youtube.com/watch?v=aZF57Bok7Ws

[nomoresonys]

Re: LG Plasma (PDP50R10101) No picture No sound

2 more from Nick's: https://www.youtube.com/watch?v=6oYj1B86y0s

https://www.youtube.com/watch?v=TwsExfR9_Tg

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

I measured a bunch of shorted mosfets. Those heatsinks are a massive paint to get off. Any tips?

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

And what replacement mosfets should I use?

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

mosfets(probably igbts actually) = use the same, watch out for fakes, there are more fake parts than real ones for sale.

a 50W soldering iron is recommended because of the double sided pcb and rivets on the pins.

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

mosfets(probably igbts actually) = use the same, watch out for fakes, there are more fake parts than real ones for sale.

a 50W soldering iron is recommended because of the double sided pcb and rivets on the pins.

I can get the solder off, the issue is so many solder legs with all the mosfets screwed in, and I can't get a screwdriver in there to get them out first. I'll keep banging on it.

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

take out the heatsink if you can't reach the mosfets

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

take out the heatsink if you can't reach the mosfets

The mosfets are screwed to the heatsink. Thats the issue.

I managed to get some out, the mosfets have 30F124 on them. I took diode readings out of circuit on 3 of them, they are turning on and off correctly, but I'm not sure what a normal diode reading should be when it is "on". I am getting 1.5v on 2 of them, and 1.1 on one of them.

[Biruslapio]

Re: LG Plasma (PDP50R10101) No picture No sound

You take everything out, heatsink + transistors/diodes.

These are not mosfets, they are IGBT, and should have no diode readings without an external gate pulse.

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

Huge props to R_J, he had linked to another thread about these TV's, and had uploaded the technical manual in that thread. That PDF is the nuts!

https://www.badcaps.net/forum/attach...3&d=1517627618

Page 78 & 79 gives the ID and diode readings of every fet on the Y sus board. I popped back in the ones I had removed and tested every one on the board (the manual says to test with the board out but fets in circuit)

There are seven different types of chips, and 23 chips in total, but after testing all of them, I found 5 bad ones, and they were all the same type (30F124). All the other fets (and 4 of the 30F124's) all tested good.

I need to take the Z board out and test that using that handy dandy manual, and then order up the replacements. The solder on this board is all awful and lead free and really hard to work with and make it look well. Any tips for dealing with it? Just keep pumping flux on it and turning up the heat?

Now the hope is I didn't damage the main board when I was messing with that.

The quest continues!

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

SO the Z board had 3 bad IGBT's on it. Two more 30F124's, so I will be getting a 10 pack of those, and one that is labeled "1K49AD". But when I google that, I can't find anything for sale that matches that part number. Anyone know where I can buy one or what a suitable replacement would be?

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

I took that mosfet out, and printed on it was 33N25T, of which I found several, so I bought a 5 pack off eBay.

Everything is in the mail now, should be here in a few weeks and we can see if this bad boy can live again!

[SluggerB]

Re: LG Plasma (PDP50R10101) No picture No sound

OK, some progress!

The replacement ICBG's finally showed up, and I replaced the faulty ones. I put the TV back together, and got the same thing: red light on front, no picture, no sound, no LED on the control board

I then unplugged the main board from the TV, disconnected the LVDS cable, plugged the TV in ... and the LED on the control board came to life!! It is giving s blink patter of 4 blinks, pause, 4 blinks, pause, etc etc

The manual does not give any blink codes for the control board, it just says "D1 Blinks Indicating Board is Functioning"

Still no picture or sound, but it seems that at least the power problem is fixed since the control board is now getting power.

I will poke around the main board a bit but if I don't see anything glaringly wrong, I will buy a replacement on ebay

[nomoresonys]

Re: LG Plasma (PDP50R10101) No picture No sound

Not really worth it, here's just another reason BUT the biggest: https://www.saveonenergy.com/green-e...ergy-go-green/ short answer, just makes MORE POISON AIR FROM BURNING COAL and negative impact on climate, china is choking on their own air and I read they are on course to at least double their coal use, with apparently no concern whatsoever for the environment. The U.S.A. is also burning way to much coal, we need to at least start with NOT BURNING COAL any longer, if not those sci-fi movies you see with people living underground and having to have oxygen tanks when they go to the surface, will be reality tv instead of sci-fi.