LG 50PJ350 plasma blowing Y-Sustain board

[Keshenatech1]

Hi, I was wondering if there's anyone here with experience on the LG50PJ350 plasma or similar models? When it came in, it had 7 shorted mosfet outputs on the Y-sustain board, Q02, 04,11, 22, 24, 26, and 28 were all dead shorted. I replaced them with the exact same type, checked their surrounding area for other open and shorted components and didn't see any further problems. But as soon as I hit the power button on the remote, I had a loud Pop! and Q22, 24, 26, and 28 are shorted out again. The other 3 seem to have survived. Someone on another forum had suggested the possibility of a shorted panel. Is that a real possibility or is there likely something else wrong blowing it out. I don't know if it's a bad signal from the control board or possibly a shorted buffer board, or a missed bad component on the Y-sus board itself. However I measured from V+ to ground and from ground to all the pins on the ribbon cable connectors and didn't see any shorts on the buffer boards. No obvious bad spots on the buffer IC's either but they're encapsulated and hard to see. Should I try a used Y-sustain board from Ebay or is there a good chance it will blow again? The Y-sustain board is a P/N EBR63039801 and my buffer boards are EBR63551603 and EBR63551703. On Ebay, someone has a set of the Y-sustain and 2 buffer boards together for only $75. The Y-sustain board is the same P/N but the buffer boards are slightly different, same part numbers except the last digit ending in 1 instead of 3 on both. Does anyone know if 01's are interchangeable with 03's? Any advice would be appreciated. I'm an electronics tech with 30+ years experience and have fixed a lot of TV's, some plasma's with the encapsulated power modules, but this is my first experience with this model. Thanks

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

No replies after almost a week. Does anyone out there still know anything about these 10 year old plasma's? Maybe I should simplify my question. Is it possible for a bad buffer board to be causing the Y-sus board to blow out? And if yes, can I measure for shorts anywhere? I still don't know if it blew out the 2nd time due to a missed bad component or something else in the TV. So I definitely want to find the root cause of the problem and fix it before blowing up a 2nd (and my last) set of mosfets. I measured for shorts between all the pins of what appear to be the driver IC's for the mosfets that blew and nothing was shorted.

[mmartell]

Re: LG 50PJ350 plasma blowing Y-Sustain board

How about following Board Protocols and posting pictures so people can see what you're dealing with ?

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

what protocols? I'm fairly new here and haven't posted much. How do I upload pictures here? Do I need to purchase a premium subscription to be able to upload large files like on Delphi forums? What do you recommend I take pictures of?

[mmartell]

Re: LG 50PJ350 plasma blowing Y-Sustain board

You do not need a premium subscription. First use the Go Advanced button instead of Post Quick Reply one.

Scroll down to where it says Manage Attachments and upload your photos from there.

A cellphone is fine. Take photos with the best light possible.

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Here are pictures of the front and back of the Y sustain board. Transistors that blew a 2nd time are still removed from the board. Also 1 pic of the entire TV with the board removed. My current cell phone has the worst camera I've ever had, just about everything comes out blurry. The Y sustain board is an EBR63039801 and there are some better pictures on Shop Jimmy's website.
https://www.shopjimmy.com/lg-ebr6303...sus-board.htm#

[dick_barton]

Re: LG 50PJ350 plasma blowing Y-Sustain board

There has been some discussion regarding fake parts on sale which you may consider.

I believe that when the Mosfets blow it can take down the driver IC's and gate resistors.

I expect you have measured the resistance between Va & VS to ground.

There's also the Ybuffer chips to test for which there are plenty of video's on Youtube showing methods.

[mmartell]

Re: LG 50PJ350 plasma blowing Y-Sustain board

I believe it is possible for a shorted buffer to take out the Ysus on this set.

I have no knowledge of this set in particular perhaps someone will chime in or simply search the model number on this site to find those threads of people who likely faced the same problem as you are having.

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Can the Z board cause the Y board to blow? I couldn't find anything shorted on the buffer boards. I measured all the T0-220 mosfets for shorts without dismounting the board from the TV. Just wondering if I need to measure anything on the back side? Those ribbons look even more delicate than the ones on the Y board and I don't want to mess with them unless it's necessary. Also, can one open gate resistor on a mosfet on the Y board cause the whole thing to blow again? Every output has 2 10 ohms in parallel for an equivalent resistance of 5 ohms. One set measures 10 so one of the 2 resistors is open. I'm not sure if I missed it the first time around or if it opened up on the 2nd blow up. I have the Y-sus board all rebuilt but I'm afraid to power it up again and don't want to let it go until I'm sure I've fixed the problem. I'll be out of spare parts after this round.

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Bottom side of Z-sus board: https://assets.shopjimmy.com/media/c...301-bottom.jpg

Top Side: https://assets.shopjimmy.com/media/c...040301-top.jpg

[dick_barton]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Also, can one open gate resistor on a mosfet on the Y board cause the whole thing to blow again? Every output has 2 10 ohms in parallel for an equivalent resistance of 5 ohms. One set measures 10 so one of the 2 resistors is open.

If a gate resistor has gone down is it possible that the gate driver IC has been damaged?

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Possible I guess. I measured between all 8 pins of all 3 drivers and nothing is dead shorted but that still doesn't mean it's not bad. I'm going to leave it sit most of the weekend in case anyone else or myself comes up with any last minute ideas. If by chance the panel itself is shorted, would I be able to measure that somehow, or would it typically only break down under high voltage?

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

I think I found the culprit. IC 70 labeled S21850 hard to read but I believe it's an IRS21850S. Anyway, there's a fairly low resistance short between pins 1 and 4, VCC and ground. I found it by comparing readings between my board and another similar board, an EBR63039802. A friend in the TV repair business gave it to me because a customer sent it to him, he doesn't work on that model, and they didn't want the board back. It was blown up similar to mine, shorted outputs, but no short on that driver IC. So what I'm trying to figure out is if I can use that EBR63039802 in place of my original EBR63039801? I got it all rebuilt but I'm afraid to power it up after that last one sounding like firecrackers.

[dick_barton]

Re: LG 50PJ350 plasma blowing Y-Sustain board

You say you found a fairly low resistance between VCC and ground of the IC but don't say what value. Does VCC also supply other IC's (components) on that board such that the fault could be at a different point.


Here's a repair kit for that board that identifies the components you need to check out.

http://www.ohmsupplies.co.uk/epages/...roducts/KIT409

LG 50PJ350
BOARD:
YSUS EBR63039801 EAX61319401

KIT409 YSUS EBR63039801 EAX61319401 LG 50PJ350
Product no.: KIT409
YSUS S/C

WHATS IN THE KIT?:

Q02
Q03
Q11
Q22
Q24
Q26
Q28

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Ok I should have been more clear, the short is on the IC, stayed with the IC and went off the board when I removed the IC. It was like a couple ohms, I don't remember the exact reading.

[tvtimmy]

Re: LG 50PJ350 plasma blowing Y-Sustain board

According to shopjimmy you can use that board. Make sure you have every screw in place before plugging in the tv.

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Is shopjimmy's information usually reliable? I saw that too on their website but was looking for a 2nd opinion. I wonder what the difference is between the 2 boards?

[tvtimmy]

Re: LG 50PJ350 plasma blowing Y-Sustain board

Their word is final, law, and 11th commandment. They know what will fit in any model. I've never been disappointed in them.

[Keshenatech1]

Re: LG 50PJ350 plasma blowing Y-Sustain board

I would like to ask for advice on something. I'm still struggling with this plasma. And the main thing that's holding me up is because I'm afraid of it. After it went off like a chain of firecrackers the first time, it sat a long time before I had enough nerve to try it again after the 2nd repair attempt to the Y-sustain board. As I mentioned above a couple months ago, I found an 8 pin gate driver IC on the Y sustain board that apparently gets damaged from the kick of the mosfets dead-shorting, location U70. On my original board, there was a Vcc to Ground short on the IC, and that same IC was quite discolored on the substitute board which also had several sorted transistors when I received it. So I ordered some from China and replaced it on both boards about 2 weeks ago, and finally powered it up with my original board last night. As soon as I plugged it in, it popped and threw a spark which scared the crap out of me again. However the screen lit up with the "no signal' message. It was a little dim and distorted, but the 1st time I've actually had video so I'm getting close. That pop and spark was a single mosfet in the section labeled "Sus_DN", location Q03, a 30F124. There's 2 mosfets in that section pretty much in parallel, Q02 being the other one, same part number. The cathodes and anodes are tied directly together and gates driven by the same source but with 5 ohms of resistors between the gates and the source on each one. (2 10 ohm smd resistors in parallel) Q03 blew apart, there's a big chunk out of it, and Q02 is fine. So I'm wondering if it could have just been a fluke or a bad one, or something else wrong that overloaded it like a bad panel or buffer. And this also may be relevant: One of the 2 gate driver resistors on Q03, the one that blew were open so the total resistance was 10 ohms instead of 5 and I caught it and replaced both prior to this last power up. They still measure good now after the transistor blew. I don't know how critical the tolerance is on these resistors and if the slight difference between the new and old ones could have attributed to the transistor blowing. Both sets measure 5.1 ohms identical including the lead resistance of my meter. I don't recall if I had replaced that transistor on my 2nd repair attempt or only the 4 on the dark heat sink so maybe it was even bad before I powered up?
I want to try the 2nd board but just wondering if there is something I should check for before powering it up again? And does anyone happen to know what the Sus_Dn signal does? I tried looking it up online and couldn't find a clear answer. As far as I can tell, this was the only transistor that blew this time around and the other 8 that I replaced still measure good with an ohm meter where they previously dead shorted on power-up.
Edit: I just figured out that I did not replace the 30F124's a 2nd time because I purchased a 6-pack of them. I used 2 in this board, 2 in the spare board, and I still have 2 left. (They were shorted when I first got the TV in and I replaced them once. 4 other transistors dead shorted on the first attempt, but not these so I left them) I should have replaced them given the open gate resistor and also because they are controlled directly by that gate driver IC. So there's a very good chance it could have been weakened and ready to blow. It also makes me wonder if I should replace that gate driver IC again in case it got and kick-back from that transistor that blew apart.

And the other thing I wanted to ask is if anyone has any advice or ideas on how I can get over my fear of electricity? I'm an electronics tech with a degree and been working on this kind of stuff my whole life (35 years into my career) but anything that pops, sparks, etc is very traumatizing to me and I'd like to be able to get over it. Most of the time when I fix something with the potential to blow up in my face, I can't bring myself to power it up and usually have someone else do it for me. At work, I'll have the floor techs go test a power supply in a machine that I'm afraid to power up on the bench. And some of them have to be loaded to regulate properly anyway. But working on scary plasma TV's at home I have no one else to power it up and I've probably wasted a couple months already just by procrastinating powering it up when I get to the point of having to test it. And the fact that it's blown on me 3 times already doesn't make it any easier. Does anyone else struggle with this fear? And if yes, what have you done to overcome it? This is very real and serious for me so I would appreciate everyone being respectful and not laughing at me or making jokes. I'm pretty sure I have some PTSD from a traumatic event that happened earlier in my life. Thanks

[sam_sam_sam]

Re: LG 50PJ350 plasma blowing Y-Sustain board

I would like to ask for advice on something. I'm still struggling with this plasma. And the main thing that's holding me up is because I'm afraid of it. After it went off like a chain of firecrackers the first time, it sat a long time before I had enough nerve to try it again after the 2nd repair attempt to the Y-sustain board. As I mentioned above a couple months ago,

And the other thing I wanted to ask is if anyone has any advice or ideas on how I can get over my fear of electricity? I'm an electronics tech with a degree and been working on this kind of stuff my whole life (35 years into my career) but anything that pops, sparks, etc is very traumatizing to me and I'd like to be able to get over it.

Most of the time when I fix something with the potential to blow up in my face, I can't bring myself to power it up and usually have someone else do it for me. At work, I'll have the floor techs go test a power supply in a machine that I'm afraid to power up on the bench. And some of them have to be loaded to regulate properly anyway.

But working on scary plasma TV's at home I have no one else to power it up and I've probably wasted a couple months already just by procrastinating powering it up when I get to the point of having to test it. And the fact that it's blown on me 3 times already doesn't make it any easier.

Does anyone else struggle with this fear? And if yes, what have you done to overcome it?


This is very real and serious for me so I would appreciate everyone being respectful and not laughing at me or making jokes. I'm pretty sure I have some PTSD from a traumatic event that happened earlier in my life. Thanks

I have ask the question is one two possible

One you have respect for electricity

Or

You have a fear of electricity

One thing that I do when I have a feeling that things might not go well with a attempt at a certain repair is to use a light bulb in series with the fuse ( with the fuse removed from the device ) or with the device and use an electronic fuse set a the amperage of the device and use an extension cord so I am back far enough so back so I can take what ever action that is needed for the situation

From time to time I have repairs not go well

I once tried to repair a VFD drive ( 480 volt 3 phase versions) that had a over current fault so I replaced the IGBT module but for some reason I did not think that this repair would be successfully so I did this power on which the VFD drive sitting on a piece of plastic turned on the power to the drive which was hook to a motor ( on the floor with a long power cord ) and power up and drive boot up successfully however when I went to pushed the button to operate the drive sparks shot out the bottom of one of the boards of this drive

that drive got trashed no more repair attempts for this drive

I have successfully replaced IGBT modules before in the past with the same kind of apprehension that this repair might not go well ( 220 and 480 volt 3 phase versions in different devices )

But I personally think that this for me is respect for what electricity can do to you if the right precautions are not followed correctly

But I can not speak to what your situation is to what you are experiencing but you might try looking at this situation with a different perspective in respect

Is it that you are afraid of the repair not being successfully
Is it fear of getting shocked
Is fear that the device will catches on fire ( on rare occasion I have had boards catch on fire but this has been very rare )

Or is it some other type of fear that you might not be aware of

The name of the game with the use of electricity is number one thing is to be SAFE to not get hurt or injured

Use long extension cord for testing devices

Use the right size fuse for the device under repair

Using light bulb in series in stead of the fuse if practical

Not touching any part of the device under test

If you have to measure voltage on the device is it practical to hook wires to the board where the voltage need to be checked ( if not is gloves appropriate for this situation or is doing this going to cause issues do this )

Stand back far enough away from the device under test on power up when turning on the device
I always try to this on devices that have had parts that have blown apart on a board

Or

If the device would not power on in the first place