Lg 42PC1R

[Mart]

Some weeks ago I was given the above plasma so I could learn a little about how they work and look to repairing it. Initially it didn't switch on, which was an easy repair to the power supply. When I got that working the picture was dark so I replaced the ZSUS IPM which gave a much better picture but with some red speckled mal discharge on dark screens. I then tried swapping the YSUS IPM to see if that improved things which it didn't. I also changed the 5 FETs with no improvement. I was going to give up at this point, so I put the set back together and ran it for a day on test. All was fine apart from the mal discharge.

I then found this forum and saw that updating the software on the CTRL PCB can improve the mal discharge so I stripped the set, pulled the EEPROM from the board to try and reprogram it, but my programmer wouldn't erase or write to it. In the end I bought a new one 29L320T from RS and programmed that. All verified ok.

I installed it back on the board the now the panel has no picture. With the auto test pins shorted you hear the familiar switching noise from the sustain boards. The CTRL board has the temp LEDs lit.

The panel is a PDP 42PC1R and the CTRL board is a 42V8&X3 6870QCH0C6C version, it says it's a PDP42X3xxxx panel, so I used the 42X3_3DCS4_88D4.bin file.

I ordered another control board to see if I had damaged it when I soldered the EEPROM back on. Whilst waiting for that to arrive I tried the file for the 42x3a, which did nothing. Not even displaying the temperature LEDs on the CTRL board. I then removed the EEPROM again and programmed the original file the tv came with. This powered up similarly to the 42X3_3DCS4 file.

I have noticed that I don't have a -Vy voltage with the CTRL board ribbon plugged in to the YSUS? With it unplugged I see -200v?

Replacement CTRL came today, when installed set behaves the same as with the reprogrammed EEPROM. Ie no picture or illumination from the panel.

I have reposted all this as I realised I hav hijacked another thread by accident. Sorry

Does anyone have any ideas what I could of done?

[Mart]

Re: Lg 42PC1R

Put a scope on the output from the little Vy inverter PCB and it looks like it is trying to start up but trips out on over current as the voltage starts to rise

[tom66]

Re: Lg 42PC1R

Could be a bad startup cap. Be aware -Vy is floating so grounding one end with your scope may trip the overcurrent.

[Mart]

Re: Lg 42PC1R

Found one of the 59N25 FETs was sc, which was pulling the -200v down when the CTRL board was plugged in. Obviously with it unplugged there was no control over the setup setdown FETs, which meant the -200 didn't get through to the 3 in parallel.
Set is now on the updated firmware, just got to check the levels.
Is there a way to make the set produce it's own full white test?

[flocko]

Re: Lg 42PC1R

Hi Mart I think this is the same is the 42PC1D if so go to menu ISM Method and select white screen, what number is the Y sus board , i am having the same type of problem with a 6871QYH053B board in that i am unable to control -Vy

[Mart]

Re: Lg 42PC1R

YSUS board is a 6871QYH053B on the sticker and 6870QYH005B 42V8&X3 on the board. When I pulled the bottom W9NK70 (for set down) and powered it up you got the -200v, this is same result as pulling the ribbon to the CTRL Board. I think the Vy is fed to the setup and setdown FETs first, then on to the 3 FETS above which work in parallel.

[flocko]

Re: Lg 42PC1R

So is the set all up and running now? i have done a deal for a full set of boards for mine i did a recap on the stand off boards and checked them out but the -Vy still sat low on white screen -167v when back on normal screen would jump to -239v, so will see what happens with the new Y sus. Did the reprogrammed EEPROM work ok

[Mart]

Re: Lg 42PC1R

Yes mine seems to be ok now. Still need to check the voltages though.
What's your Vs doing when the Vy is fluctuating?

[flocko]

Re: Lg 42PC1R

Hi Mart
Vs 186v no fluctuation to ground
Va 60v " " " "
-Vy -167v to -239v across -Vy test (resistor)
Vsc 120v no fluctuation across Vsc test (cap)
Ve bias 100v no fluctuation Ve bias test to ground
I have changed all the caps on the Y sus board , checked all components and have now put my hands up and given in till the new board gets here

[Wendy]

Re: Lg 42PC1R

Hi,

Morning everyone.

I have read thru' some of the threads and posts here that some of you have actually tried replacing the IPM of the Y-sus board of the LG Plasma Tv 42PC1R.

I have a LG Plasma TV 42PC1R and am trying to replace the IPM of the Ysus board (Model : 6871QYH053B ), cos got sound but no picture and still the same after replacing a blown fuse on the Ysus board. The part no. for the IPM as indicated on the board on the heat sink is : 4921QP1050B (for the IPM).

When I tried to order the part online, the seller asked whether i want the VB R1 or VB R2 for the IPM ( apparently there are the R1 or R2 kinds for the IPM ). Thus, would appreciate if anyone here could help as to whether our LG 42PC1R should be using the R1 or the R2 IPM ?

Also, can someone please be kind enough to enlighten me on how to test or check the Ysus IPM using a analogue multimeter ( the kind with the needle as gauge ) as to whether they are working or has gone bad ?

Thanks in advance.