Plasma Y-MAIN board LJ92-01200A

[cadar21]

Re: Plasma Y-MAIN board LJ92-01200A

i was wondering if you guys had the diagram of the capacitors for this board Y-MAIN board LJ92-01200A...

i need C5052
and C5040...

[mmartell]

Re: Plasma Y-MAIN board LJ92-01200A

I'm sure there's a rational explanation for that, lol. I would check the voltages on theymain against what's printed on the panel. Or could be xmain trouble as well.

You need an expert opinion so I'll just bow out now.

[adam699]

Re: Plasma Y-MAIN board LJ92-01200A

Please see the attached image. I replaced the faulty diodes, resistors and mofset. I'm trying to run the TV with only the upper buffer board and this is what I get. (See picture) any ideas?

[adam699]

Re: Plasma Y-MAIN board LJ92-01200A

Anyone else?

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Sorry I can't help you, my TV was disassembled and disposed of being I ran out of help and know-how.

Good luck.

[adam699]

Re: Plasma Y-MAIN board LJ92-01200A

Hello,

I'm sorry to resurect an old thread but I'm trying to fix my TV and came across this.
The TV originally had sound but no picture.
I replaced the IPM (althou it wasn't blown as it turned out) and one of the blown mofsets.
The buffer boards are not shorted at this point althou I'm positive the lower one was the culprit as one IC is visibly burned out.
At this point I'm getting a reddish distorted picture with lower part of the low buffer visibly blown.
I checked the diodes and the resistors as specified in the thread and both resistors are burned as well as both D5018 and D5009 diodes. I was able to cross reference the markings on the D5018 but cannot find anything on the D5009 (says K7 79 on it) I have a K7 59 on a parts board that I could use. Can someone tell me if that would work or what the right specs are. Also the resistors are both 1ohm in paralel so .5ohms. Is it ok if I substitute them with one .5 ohm?

Thanks in advance.

Adam

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Anyone have any idea what I should check next ?
Thanks.

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Any ideas what to check next. Thought I was doing good =\

[tom66]

Re: Plasma Y-MAIN board LJ92-01200A

OK, yes, that makes sense, it is for the control/logic board.
Since the voltages disappear if that is connected, I expect you still have a fault on your Y-main.

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Where does the small ribbon cable go?

It is the small cable below the power cable connector.
I am assuming the ribbon cable is a signal / controller cable, while the other is power.

[tom66]

Re: Plasma Y-MAIN board LJ92-01200A

Where does the small ribbon cable go?

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

I get 194.5 at the black wire in the power connector on the y-sus for a brief moment and then it goes away once the TV clicks to standby.

If I do not plug in the small ribbon cable below the power connector on the Y-sus, it will stay on and read 194

Whats next ? =)

[tom66]

Re: Plasma Y-MAIN board LJ92-01200A

Do you have VS reaching the Y-main board?

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Got my 3 new mosfets installed. Didn't do too bad getting them straight and flat.

Plugged the board into the TV with no buffers.
It still clicks on, then off and the green LED flashes.

I don't appear to have any shorts across either of the 2 black connectors. I checked the few hot pins vs all the ground pins on each connector.

I did notice that my new mosfets measure O.L. from the Gate to Source and from Gate to Drain. The existing mosfets measured about 14M ohms Gate to Drain and 2-5M ohms from Gate to Source.
The New and Existing mosfets all measured about 6.37M ohms Drain to Source. None of them make the meter beep though when on diode check mode for ohms.

So, what do I need to check next ?

[tom66]

Re: Plasma Y-MAIN board LJ92-01200A

It's not a good idea to run the board without certain parts unless you're sure no damage will occur.

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Once I remove this 3rd, bad mosfet, can I plug the board in to see if it will "not" trip the tv into standby, or is that going to harm something else with out the mosfets attached ?

[tom66]

Re: Plasma Y-MAIN board LJ92-01200A

Yes it's very dead.

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Got all the paste cleaned up.

I then retested to double check...

I have one mosfet that reads 1.3 ohms between Gate and Source
It reads 100.1 ohms between Gate and Drain
It reads 99.2 ohms between Drain and Source.

Does this one need replaced too ?

[SevillianSTS]

Re: Plasma Y-MAIN board LJ92-01200A

Hi,
pretty good question! I´ve read and learned alot from reading different posts in this excellent forum. I take my hat off to all the plasma and lcd gurus here! Great job and thanks!
I myself have abt 30 years of experience with crt tv´s, now getting familiar with lcd´s, but plasmas are still a book of seven seals to me. This one stood in my garage for abt 3 years, not knowing if it is worth the time to look for. Anyway, with the help of this forum i gave it a try and let´s see what happens.

While you are waiting for the mosfets maybe you can prepare the heatsinks for remounting. Same here, the thermal compound is as hard as a stone, no way to get it off with alcohol or something like that. I used a sharp scalpel to scratch it off. Worked fine for me but be careful not to make any deep scratches into the surface of the heatsinks. Did the same with the residue on the mosfets.

Did you encounter any probs with your buffer boards? I could locate one defective driver ic on the upper y-buffer board after removing those little heatsinks on them. The defective one had a little hole on its surface and after removing it from the pcb the resistance between supply rail and ground measured good.

yes, the lower y-buffer has a shorted IC

[PL519]

Re: Plasma Y-MAIN board LJ92-01200A

Hi,
pretty good question! I´ve read and learned alot from reading different posts in this excellent forum. I take my hat off to all the plasma and lcd gurus here! Great job and thanks!
I myself have abt 30 years of experience with crt tv´s, now getting familiar with lcd´s, but plasmas are still a book of seven seals to me. This one stood in my garage for abt 3 years, not knowing if it is worth the time to look for. Anyway, with the help of this forum i gave it a try and let´s see what happens.

While you are waiting for the mosfets maybe you can prepare the heatsinks for remounting. Same here, the thermal compound is as hard as a stone, no way to get it off with alcohol or something like that. I used a sharp scalpel to scratch it off. Worked fine for me but be careful not to make any deep scratches into the surface of the heatsinks. Did the same with the residue on the mosfets.

Did you encounter any probs with your buffer boards? I could locate one defective driver ic on the upper y-buffer board after removing those little heatsinks on them. The defective one had a little hole on its surface and after removing it from the pcb the resistance between supply rail and ground measured good.