LG Plasma 50PC1R-ZH

[Nikoopriest]

Hello everyone!

I bought a broken LG Plasma few weeks back thinking I could fix it. I have repaired computer LCD's before that had bad caps and from the sympoms of this TV it sounded just like that would be the case. But no..

When I try to power the TV on the red standby led on the front of the tv starts blinking in white and I can hear a relay clicking. It only clicks once and then it powers off again. It will not start up, dosnt matter how many times I try.

I could not see any bad caps during my visual inspection of the PSU so I bought a new one and replaced it. I get the same symptoms as previous.

This repair project is beginning to cost what a brand-new tv would cost today and the I can feel the axiety growing within me.

I also measured the resistance of the 3 5x20mm fuses and they seem fine.

So what I've got so far is a TV with OK PSU and fuses but it still wont turn on. The clicking noise of the relay is becomming a nightmare.

I call myself a "hobby-solderer" and I have no real experience with these kinds of things. I have borrowed a multimeter but I dont know where to use it except from measuring the fuses.

I've been at every possible forum on the internet searching for help but none seem to be able to help me. If someone can help me get my TV working again I will pay you half your weight in beer. That applies to everybody (note that no actual beer will be sent, only the money it would cost in your country).

So I beg of you, please save me from this misery and help me get my tv working again!

Yours sincerely,
Nikoo

[tom66]

Re: LG Plasma 50PC1R-ZH

Check the AC detect pin (ACD or AC_DET.) I suspect it is dropping out, causing issues... Should be 5V all the time.

[Nikoopriest]

Re: LG Plasma 50PC1R-ZH

Check the AC detect pin (ACD or AC_DET.) I suspect it is dropping out, causing issues... Should be 5V all the time.

What am I looking for, where can I find it and how do I measure it?

[scokljat]

Re: LG Plasma 50PC1R-ZH

I bought a broken LG Plasma few weeks back thinking I could fix it. I have repaired computer LCD's before that had bad caps and from the sympoms of this TV it sounded just like that would be the case. But no..

Welcome to club, Nikoo. I also recently bought an old 42" LG plasma on a flea market for 8.3$ hoping that I'll change some caps like I usually do when repair LCD's for my friends... But NO ;-) Now, I learned a lot about plasmas and I'm waiting for some parts to arrive to fix faulty Y-SUS board. My advice is to try fix it on the component level. Buying and swapping boards inside without knowing principles how plasma work can be very expensive business ;-)

First you have to learn how plasmas work. It's completely different than LCD.

Each plasma TV consists of:

- branded chassis with speakers, buttons, LED's (Sony, Panasonic, LG, Samsung, Pioneer....)
- main video processing I/O board with tuner, video and audio I/O switching, audio amp, video decoder and processing, menu's, firmware...
- plasma module

Plasma module consists of:

- plasma panel/screen
- power supply (PSU)
- control board
- YSUS board (sometimes contain IPM module)
- ZSUS board (sometimes contain IPM module)
- Y buffer board's
- X buffer board's
- some models have sub PSU and maybe other sub boards

IPM (Inteligent Power Module) modules are hybrid IC's, consists of lot of FET's, diodes and control circuitry all bundled in a small package. They run very hot and are prone to failures. IPM modules are present on Y-SUS and Z-SUS boards. Your TV has two IPM's on Y-SUS and two on Z-SUS. Some plasmas use standard FET's and diodes rather than IPM modules which is easier to troubleshoot/repair and fails less frequently.

There are hundreds of plasma TV manufacturers and models but only few plasma module manufacturers. If you buy Pioneer, Panasonic, Vivax, Sharp, Philips etc... plasma TV you will probably end up with one of Samsungs or LG's or other plasma modules inside. Your 50PC1R-ZH TV incorporates LG PDP50X3 plasma module.

Studying this forum, I also learned that sometimes problem is not only in one board or component. On some models bad Y-SUS board can destroy buffer boards and vice versa, so you have to fix them or replace both if you don't want to destroy them again.

There are lot of dangerous voltages (up to 200VDC) inside plasma module across all boards so you have to be very cautious. Vs, Va, Vsc, -Vy, Vzb are first that you have to check or adjust when troubleshooting plasmas. There are also lot of low voltages like +5V, +3.4V, +15V, +12V etc...

First thing you have to do is to get all required voltages from your PSU. If FET's on some boards are shorted, it will probably blow some fuse and produce a voltage drop or activate PSU protection circuits so TV will stay off indicating some error with LED's.

In your case, good start would be:

- find and study the service manual for PDP50X3 plasma module
- search this forum for other posts about PDP50X3 plasma module
- check all fuses (snap in and SMD)
- check all voltages
- disconnect board by board and see if you get missing voltages or change TV behaviour
- check all FET's and diodes on suspected boards
- make quality photos of all boards and post your notices on this forum so people can help you


For a quick start here is:

Service manual for your TV LG 50PC1R-ZH:


Excellent plasma training manual for various plasma modules:
https://cdn.badcaps-static.com/pdfs/...c144a4cf1a.pdf

Please, sorry on my bad English, I'm Croatian...

Cheers!

Suad

[Nikoopriest]

Re: LG Plasma 50PC1R-ZH

Hats off to you Suad!

I will look into this as soon as I have some spare time and I will post a report of what I've found.

As far as your english goes I think it's perfectly fine

Thanks alot for your well written post, it means alot that somebody is willing to help! And tom, I will try to take readings from the AC detect pin!

[Nikoopriest]

Re: LG Plasma 50PC1R-ZH

So.. I've been quite busy lately but now I'll have a go on the TV again.

I heard that the Y-SUS boards are prone to failure. I am thinking of replacing it since I'm not very good with the multimeter.

If the Y-sus is defect, would disconnecting it result in the TV starting up? Because I've tried to disconnect it but I get the same problem, the famous clicking noise and then back to standby.

Thanks in advance!

[tom66]

Re: LG Plasma 50PC1R-ZH

Try with Z-sustain disconnected. Both are common failures. Bad Y-sustain or Z-sustain can stop the TV starting up.