LG 42PC1D plasma - clicking repeatedly

[pecrie]

Re: LG 42PC1D plasma - clicking repeatedly

@tom66 ,

didn`t know ,this tv had the main and av board ,as 2 different boards.Well glad to hear ,that you sorted it out

[tom66]

Re: LG 42PC1D plasma - clicking repeatedly

@tom66 ,

didn`t know ,this tv had the main and av board ,as 2 different boards.Well glad to hear ,that you sorted it out

Yeah I'm guessing the separate boards are so they can sell a US and European version and change only a small 2 layer board instead of a large complex 4/6 layer board.

[pecrie]

Re: LG 42PC1D plasma - clicking repeatedly

@tom66 ,

Well good job ,you got it to show a picture.But here`s another question.I think that you have far more experience ,in doing measurements with a scope.Is there a preferred method?

I mean ,do you connect the tv to an isolating transformer ,and the scope directly to the mains ,and then take measurements?

Or is the tv on the mains ,and the scope connected to the mains ,through the isolation transformer?

Do you have a preferred method ,for this?

thanks for your suggestions ,answers.

[tom66]

Re: LG 42PC1D plasma - clicking repeatedly

@tom66 ,

Well good job ,you got it to show a picture.But here`s another question.I think that you have far more experience ,in doing measurements with a scope.Is there a preferred method?

I mean ,do you connect the tv to an isolating transformer ,and the scope directly to the mains ,and then take measurements?

Or is the tv on the mains ,and the scope connected to the mains ,through the isolation transformer?

Do you have a preferred method ,for this?

thanks for your suggestions ,answers.

Well, I haven't used an isolation transformer properly yet, but I did get one for later use, as well as a variac. I haven't yet had a need to probe the primary. In this case, it might have been useful to probe the primary, but I was able to fix it without doing so. When dealing with the secondary, including the sustains, there is no need to use an isolation transformer, however there are high voltages present so I highly recommend a scope capable of surviving 400V and a 10X probe capable of at least 600V - just in case something goes wrong.

[tom66]

Re: LG 42PC1D plasma - clicking repeatedly

There is one minor side effect of removing the AC detect. That is the speakers do not mute on power off. If you pull the plug out with a bright picture, you hear a rather loud popping sound. This is normal with some types of amplifiers if the power suddenly drops out. If the picture is dim you hear nothing. As the TV will be mostly plugged in 24/7 in standby, I don't think it is a major issue.

I figure this is caused by the audio supply (which runs off the main 540uF (270uFx2) bulk capacitance) dropping out before the standby supply (which runs on 68uF.)

I have managed to get rid of most of the sparklies. A few still remain but they are difficult to notice from a distance. I'm quite happy with the picture on this plasma. Very vibrant and colourful. Better than LCD, just about - honestly though not really worth the substantial price difference. (Although for larger screen sizes, prices are far more reasonable.)

[pecrie]

Re: LG 42PC1D plasma - clicking repeatedly

thanks for the info.I don`t have a variac or isolating transformer yet ,but will get them.Yes these voltages are very nasty

[slappala]

Re: LG 42PC1D plasma - clicking repeatedly

I bought amp meter few weeks/ a month ago to get better idea of the situation.
Chassis ground had some AC in it to back up the conclusion of y-sus or z-sus board leaking some current in start-up situation. (Not the caps)

The amp meter was faulty so I'm waiting the new one to arrive to be sure.

A/C detection is not there for fun..it's for safety also. That 's why I did not by pass the protection scircuit..(plus the dots)

measure the chassis voltage levels DC and AC againts ground when starting the TV..

[Anton_Olsson]

Re: LG 42PC1D plasma - clicking repeatedly

Great to hear you got it to work! I got the exact same set with the exact same problem. Being quite inexperienced in the electronics department so far all I have done is replace the 9 3300uf caps, of wich 5 was noticably bulged. Could you snap a shot of the fix you did? I got no clue how to solve this on my own...

[tom66]

Re: LG 42PC1D plasma - clicking repeatedly

Great to hear you got it to work! I got the exact same set with the exact same problem. Being quite inexperienced in the electronics department so far all I have done is replace the 9 3300uf caps, of wich 5 was noticably bulged. Could you snap a shot of the fix you did? I got no clue how to solve this on my own...

Sorry, the TV has since been buttoned up and will soon be sold, however if you post a picture of your power board from the bottom I'll show you where to make the bodge.

[Anton_Olsson]

Re: LG 42PC1D plasma - clicking repeatedly



/Anton

[tom66]

Re: LG 42PC1D plasma - clicking repeatedly

Please don't post pictures inline.

First check if AC detect switches off or is unstable. It should be a fixed 5V.

I think it is these two optocouplers but just to be sure they are the only two on the board facing the other way around. Bridge the pins on the secondary side using some solder.

This will disable AC detect so you may get a popping sound when the TV is unplugged while running but that will not happen if it is switched to standby or unplugged in standby.

[Anton_Olsson]

Re: LG 42PC1D plasma - clicking repeatedly

It was the two above the red markings, in case someone else is trying this out. Worked great for me. Thanks a million.

[tom66]

Re: LG 42PC1D plasma - clicking repeatedly

It was the two above the red markings, in case someone else is trying this out. Worked great for me. Thanks a million.

Great to hear! Sorry I got them wrong but you figured it out in the end. Clearly, it seems to be a common problem .

[slappala]

Re: LG 42PC1D plasma - clicking repeatedly

I changed the y-sus board STK chip and it looks to be working now with the protection circuit still intact with less red sparks.

Still testing for durability this week before saying it's fixed for now.

STK chip was about 20$ from ebay..

I have tested a lot of the caps and I see bigger ESR readings with my meter and I think the high voltage caps have bigger ESR values than you might think..check the specs from datasheets.

See my thread for changing the STK chip if you go that way.

[slappala]

Re: LG 42PC1D plasma - clicking repeatedly

Ok, today the same symptoms appeared again.. :/
It's freaking wierd. maybe I'll try to bypass the AC detection..

[fp8915]

Re: LG 42PC1D plasma - clicking repeatedly

Hello everybody,
I want to say thanks to tom66 for opto-bypass solution.
It solved my problem with LG 50PC1R with stdby red led always off and few seconds blinking power white led when I tried to get power on by remote control (without any click from relays)..

Thanks a lot

[iadrian]

Re: LG 42PC1D plasma - clicking repeatedly

Sorry for opening an old thread but I am having the same problem with my LG-42PC1R.

I have read the solution althought I don`t understand it.

Can someone explain to me what do you mean when "opto-bypass solution" ?

Thank you in advance!

Did Tom66 made a tutorial on this problem maybe?

[ViperRunner]

Re: LG 42PC1D plasma - clicking repeatedly

Thanks for sharing the information Tom66!!

I used it to repair my 6709900023A with success!

Best regards

[YLG80]

Re: LG 42PC1D plasma - clicking repeatedly

Old thread, but still alive !
Thanks to Tom for his tip on the optocouplers.
I shoudl have tried that first because it took me 3 days to find waht he was found before.
In fact the symptom was not the same :
- Connect the LG Plasama to the mains.
- Front LED becomes steady RED.
- Use the remote to wake up the TV. The RED led goes steady OFF

Disconnect the mains.
- Remove only the P800 cable that goes to the MAIN BOARD.
- Connect the device to the mains ... and wait about 3-4 minutes.

You would hear the activation of the relays and if you are in the darkness you will see that the screen is slightly illuminated.
That means at least that Y and Z boards are OK.

I have the Power board schematic so I've tried to trace why pin 20 of U701 (AC DET) was not going up to 5V. (Once only, it got up to 5V after a few minutes)
I've replaced P501 and P502 optos to no avail.
I guess that the problem comes from the regulators U131 and U312 but I've no replacement.
So I finally decided to short pin 3 and 4 of both optos and the TV works like a charm.
Thanks again Tom fro the tip.

[fzabkar]

Re: LG 42PC1D plasma - clicking repeatedly

I have the Power board schematic ...

I would really appreciate the PSU circuit diagram.

I'm going mad trying to track down an intermittent startup fault on a friend's LG 42PJ350 plasma TV. The TV clicked when I first tested it but has worked unfailingly after I took the back off. I'm convinced that the area around U701 is somehow responsible. BTW, I have heated the PSU with a hair dryer and I've resoldered all the usual suspects (coils, transformers, ceramic resistors, power semis).