LG 42" Plasma (will enter Model number later)

[MadElectroScientist]

Hello, I have a LG 42" Plasma my neighbor gave me because it failed on him and was going to be cost prohibitive to have it professionally repaired...

I was hoping for some assistance using this forum but wanted to get an idea id anyone was interested in assisting before I dug up all the information about the TV heh...

Long and the short of where I was and where I am now with the TV is, I got it, powered it up, lights were on but nobody was home (no display), opened it up, found a blown fuse on the Y-SUS board, replaced it, almost shit my pants when it blew again and I saw the miniature fireball appear near the fuse, decided that was stupid, and then continued to look into the issue online...

Ended up taking the board out and taking off the "Hybrid IC" I believe it is called, and replacing with a $45 Sanyo one off of eBay.

Removal of the old IC was successful and new IC went on well, old IC actually had a FET or something which exploded out of the bottom of the chip, so that was "comforting" seeing that after I had spent so much time trying to get the old chip out.

I also added some higher performance thermal compound as the old stuff had dried to dust.

The unit powered up fine after that, I got a bouncing No Signal box on the screen. All seemed well until I looked at the image a little closer and noticed the characteristic red sparkles on the screen. I have shelved it since then because my understanding is I need to tweak potentiometers and I'm a little apprehensive of getting in there with the unit on and playing with the high voltages (I'm also scared of that fuse!!).

I was doing a little research on resolving the sparkles and stumbled onto this forum and saw there were some very knowledgeable individuals available on this forum and was hoping for some assistance...

To this date the set has not been powered for more than 15 seconds or something because I read about "buffers" potentially taking out the Y-SUS board and how the Y-SUS board and Z-SUS boards are supposed to be replaced in pairs, also the hybrid IC is used on both boards so should I just go ahead and replace the one on the Z-SUS board or us it until that one blows, or is that going to take out the new hybrid IC on the Y-SYS I just replaced, also I was supposed to check a Rs voltage I think and make sure it is 205V or something.... So with all these unknowns and the apparant risk of blowing the Hybrid IC I just put in it has been sitting until I feel adventurous enough to get inside it again...

So if there is interest or this sounds like an easy fix, I'll provide as much info as I can once I get home!

Thanks!

[el3ctroded]

Re: LG 42" Plasma (will enter Model number later)

The thing about replacing both Y and Z boards, AFAIK is just the Zsus board is likely near failure since the Ysus board went. Likely due to the thermal compound issue you found on the Ysus. Planned failure? Maybe.

Testing the voltages is easy to do, once the screen is on just do it. Just make sure your meter leads don't slip. What I did was power up the screen, test voltages, power down, adjust pots, power up screen again until it was right.

The red sparkles I found were greatly reduced by adding cooling to the Ysus board and adjusting the Vs voltage.

I've read that the heatsink on the hybrid ics are too small so adding a fan will make it last longer. I just used an 80mm PC case fan and attached it to a 12V wall wart style supply.

The buffers are likely fine since you got display. If they were bad, you could have taken out the Ysus board again.

[PlainBill]

Re: LG 42" Plasma (will enter Model number later)

I believe the usual recommendation is to replace the Y-sus and and Y buffers at the same time. At a minimum you should examine the chips on the buffer carefully for any sign of damage.

Go on Scribd and search for the LG Plasma Quick Reference Alignment Handbook and follow the directions for setting up your particular panel. Use an insulated screwdriver, and keep one hand in your pocket. It is not a bad idea to have an assistant standing by to dial 911 just in case something goes wrong.

As an aside, the model number of the TV should be on the back panel. That helps us help you.

PlainBill

[MadElectroScientist]

The P/N was buried as the TV was buried behind all of the rest of my to-do projects, but now that I uncovered it it is:

Model Number 42PC3DC-UD.A
Manufactured June 2006
Chassis PA-51D

I appreciate the hand behind the back someone nearby with 911 on speed dial warning, but if I felt that inept with electronics I wouldn't be on this forum

Besides, that was the warning for back in the day when the residual charge on a CRT could seriously F* you up if you were holding on to chassis ground and completed the path to the CRT anode right?

I know Plasmas operate by means of glowing balls of gas, (which generally requires high voltages to ionize gasses, bring to a higher energy level, when they lose the energy they crap photon bla bla bla)-- but are there residual high voltages in Plasma Displays? I really don't know that answer, maybe on the power boards (generally accessible only by removing the board and carelessly handling), but not the actual panel display right?

And I appreciate the suggestion to power it up for brief moments and adjusting incrementally, was reading in some places you gotta make the adjustment after it has been running for 30 min but I'm sure I can improve it from where it's at right now by running the adjustments with it cold, then when convinced Vs is stable, then run it through a burn-in...

I have never used Scribd before but I'll take a look for that handbook, sounds promising.

Oh and yes I was considering active cooling for both IC heatsinks, I got some pretty nifty small, quiet 3.3v fans with a side discharge I was thinking of using, they may not move a ton of air, but I think some is better than none as in the present case... Just gotta find a voltage rail which energizes with the panel, can be regulated down and can handle ~50mA additional loading heh...

[MadElectroScientist]

Re: LG 42" Plasma (will enter Model number later)

Oh and something that has been nagging at me since I heard a friend mention it...

Someone told me "Oh yeah Plasmas are nice but I couldn't ever get one because they have that one huge fault where they cannot ever lay down horizontal on a surface, because if they do the screen is shot, you throw it out-- that's why they are always shipped standing up in the boxes".

I find that hard to believe for many different reasons, but I was wondering if anyone here knew where or how that kind of information about Plasmas would come from?

[PlainBill]

Re: LG 42" Plasma (will enter Model number later)

Oh and something that has been nagging at me since I heard a friend mention it...

Someone told me "Oh yeah Plasmas are nice but I couldn't ever get one because they have that one huge fault where they cannot ever lay down horizontal on a surface, because if they do the screen is shot, you throw it out-- that's why they are always shipped standing up in the boxes".

I find that hard to believe for many different reasons, but I was wondering if anyone here knew where or how that kind of information about Plasmas would come from?

Urban legends abound. That one probably came from a TV salesman who was getting a bonus for every LCD set he sold.

You do want to be very careful when laying them face down. As a matter of fact, if that TV has the original stand, take a look at the diagram on the bottom of the stand.

The 'one hand in the pocket' rule is more valid for plasma sets than it ever was for CRT sets. The second anode voltage on a CRT could give you a good jolt, but the current was well under 1 mA. By choosing the appropriate points on a plasma set you can get over 400 volts at .1 amp, enough to stop your heart.

Not to mention the guy here who was trying to tweak something with a metal screwdriver without taking the back off the set. He managed to short something out. I'm not sure if he ever got it working again.

PlainBill