LG 42" Plasma TV model 42PT350R with darkish image and sparklies

[angelos]

Hi guys. I need your assistance once again. I have this tv whose y-sus board had some shorted out igbt's. I replaced all faulty stuff and then the tv came on. I just saw a bad dark picture with sparkles.
I wrote down all the voltages which seemed spot on.
They are,
Vs=201V
Va=55V
Vy=-200V
Vzbias=125V
They match what is on the panel.
The only other thing and i took a photo of is the fact that the plasma display has a yellow tinge instead of a matt black color. I suspect that to be panel ageing.
Why is my picture so dark and sparkly...?

Kind regards
Angelos

[angelos]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

So sorry. I realise now i put this on the wrong thread. Ive veen using my cell phone and everything is so small i couldnt read well the heading. Shouldbi repost?

[Per Hansson]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Thread moved

[Andrew F. Ali]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Look for loose/cold solder joints on the Z-Sus Bd.

[angelos]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

I just want to get the terminology right. Is the zsus also called the xsus. The one with the two wide ribbons on the right?

[R_J]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Looking from the back, Y-sus is on the left and Z-sus is on the right, a few mfg. call it the X-sus, then there is Panasonic

[angelos]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

I have a proper digital storage oscilloscope. What kind of a waveform can i measure to ensure proper operation. I have a x100 probe if need be?

[angelos]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Hi Guys, just an update. I have not had much time lately to continue with this tv but i did notice something. If the TV has been switched off for a couple of days then when you power up the TV you get the following image which progressively improves. I attached a photo for you to see. Would you still say it's the Z-Sus or X-Sus????

[chrismurphy]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Z-sus issue Faulty or very bad joints

[Andrew F. Ali]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Since this is a LG TV it is properly called a Z-Sus Bd.

[angelos]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

Well about 5 minutes after taking the photo the ysus board short circuited again. Are there repair kits for these available?

[tom66]

Re: LG 42" Plasma TV model 42PT350R with darkish image and sparklies

It failed because you are running it for too long with a bad z-sus, this will cause extra stress on the board because of the lack of energy recovery. These cheaper TVs use a shared energy recovery circuit to reduce costs but it can make for tricky repairs.

Repair kits are availability but availability in South Africa may be the issue.

You can replace the IGBTs and gate driver ICs that have failed - UTSource is a good place to go