LG Plasma 50PA5500

[Dabbi]

So we had a really bad storm the other night and now my TV doesn't work. Everything else on the surge protector still works though. What happens is I plug the TV in and it will come on for maybe 30 seconds or so. Picture is fine sound is fine. Then the screen just goes black and the sound quits, but you can still tell its powered the screen is just black. It will not respond to the remote or buttons on the tv. The only way to turn it off is to straight unplug it again. Then I have to wait a good twenty minutes or so before it will do anything again. Would appreciate some thoughts or advice on this, as I've never really dealt with this before.

[capkid]

Re: LG Plasma 50PA5500

It sounds like you have power supply or main board issues - possibly both. You'll need to open it up to investigate further.

[tom66]

Re: LG Plasma 50PA5500

If you open it up, there is a quick and simple way you can determine if it is a main board fault. It would be very unlikely that the storm did this, it is more likely a coincidence than not.

[Dabbi]

Re: LG Plasma 50PA5500

Most likely I won't have time to open it up till tomo. Can you tell me what I need to look for?

[tom66]

Re: LG Plasma 50PA5500

You should provide some pictures of inside the TV ("the chassis") so we can see what parts are inside the TV. Ideally one of the overall layout, one of the "LG Electronics PDP 50R123456789" sticker (inside the unit not on the rear) and one of each major, large circuit board.

The test only requires a bent paperclip or a small piece of wire, to engage the test point which can be marked on the photos.

[dyel]

Re: LG Plasma 50PA5500

Hi All,
Sorry for interrupting into your thread, but I'm trying to fix my 50PA5500 either. Today I was a bit shocked with the price to fix (almost 80% of the TV price), so I thought that maybe it was better just to buy a new one.
I have no experience with TV repair, but if it just requires to change, say, power supply, then I can do it. Only one thing left - just find out if the problem is really in the power supply.

I have the same problem mentioned in the thread - https://www.badcaps.net/forum/showthread.php?t=29021.

Reading this thread, I got that there is a quick test. But you need some photos. As the author has not provided, so let me.

[Dabbi]

Re: LG Plasma 50PA5500

okay here are my inside pics

[tom66]

Re: LG Plasma 50PA5500

OK, this will apply to both of you.

Unplug the power to the unit from the plug.

Disconnect the red highlighted connector (covered with tape.) Keep the tape, you'll need to reconnect this later.

Place a wire jumper across the other highlighted points - EXT AUTO GEN.

Power up the TV.

You should see a test pattern, something like this although it may vary slightly:
http://www.youtube.com/watch?v=xgrvRc2JVVQ

If you do, the problem is almost certainly the main board (99%), so you can replace it and your TV should be fixed. After replacing it, I recommend installing any firmware updates that LG have supplied, which may make it more rugged.

[tom66]

Re: LG Plasma 50PA5500

For reference, this is the main board, the above board is the control board.

[dyel]

Re: LG Plasma 50PA5500

Followed your steps. I did not have the TV switched on and the pictures like in http://www.youtube.com/watch?v=xgrvRc2JVVQ.
Only sound like "click-click-click" in the power supply.
Seems that I need to change the power supply.

[tom66]

Re: LG Plasma 50PA5500

With everything back to normal, can you see the screen lit up in the dark (when power applied)? Or does set just click-click? More likely to be main board or sustain board than power supply.

[dyel]

Re: LG Plasma 50PA5500

1. When everything at their places and power applied the following happens:
- Click-click in the power supply;
- Red light in the main board (switched on/off between clicks);
- No red light in front of the TV (indicated that power applied).
2. When I tested with a paperclip the following happened:
- Click-click in the power supply;
- No red light in the main board (it was disconnected);
- Red light in front of the TV (indicated that power applied), but the screen did not show any sign of life.

If "the screen lit up in the dark" means the "red light in front of the TV", then I mentioned above. If it means that the screen should, say, wink, then no - the screen is completely black.

[tom66]

Re: LG Plasma 50PA5500

I meant that the screen glows slightly when powered, but in this case, it apparently does not. In which case you will need to make two jumpers on the power supply to turn it on. You will need to acquire some resistors with leads ("through hole resistors.") Any value from 100 ohm to 470 ohm is usable, but lower is better.

There is a grid of pins on the power supply. The connector must be unplugged on the main board end (the board with video inputs) and left connected to the power supply.

Resistor must be connected between STBY and M_ON and STBY and RL_ON; the jumper on the control board should also be present and the appropriate cable unplugged too.

Then the screen should come on and show test patterns if it is a main board issue, otherwise it may be a power board, sustain board, or other fault.

[dyel]

Re: LG Plasma 50PA5500

Now it's a next level .
1. Could you provide a picture of a resistor with leads ("through hole resistors.") (sorry, but I'm ignorant in this question). I googled it and got some picture about it.
2. "There is a grid of pins on the power supply. The connector must be unplugged on the main board end (the board with video inputs) and left connected to the power supply." - it's easy - done;
3. "Resistor must be connected between STBY and M_ON and STBY and RL_ON" could you show in the picture, what spot should I put a resistor? (I attach the according file);
4. " the jumper on the control board should also be present and the appropriate cable unplugged too." Now I know what is that "power supply", "main board" but do not know where "control board".

[tom66]

Re: LG Plasma 50PA5500

Here are some resistors. You can buy them from RadioShack, Fry's and other electronic shops. Buy the smallest or second smallest you can. If the clerk asks, you want a "1/4W 5% carbon film resistor" ("one-quarter watt five-percent") with a value of "100 ohms" (but if they don't stock those, try 120, 150, 180, 220, 270, 330, 390 and 470 ohms.) Should be under a dollar for around 10 resistors.



As for the connector, you'll need to bend the leads of the resistors and put them how I've highlighted. Get them in the right pins but the exact position isn't critical and they can go either way around (i.e. they are not polarised.) Try to make sure that they don't touch each other. NOTE: This image assumes the blue wire is in the place I've highlighted; if not, flip/rotate the connector until it is or you may damage your resistors or power supply.

The control board is the board you put the EXT AUTO GEN jumper on. In this instance, you want to leave that jumper in place and also keep the cable that connects between the main board and control board disconnected.

[dyel]

Re: LG Plasma 50PA5500

Now it's almost clear what to do next.
Only one concern regarding to the note "this image assumes the blue wire is in the place I've highlighted".
The blue wire is in the place I've marked. Should I still follow the schema you drew?

[tom66]

Re: LG Plasma 50PA5500

In which case follow this diagram.

[Dabbi]

Re: LG Plasma 50PA5500

well I was having trouble keeping the bridge connection constant, kept slipping off the points. but I did get it to give me a little at one point, it flashed a white screen several times and did the solid blue red and yellow screen then went black again.

[tom66]

Re: LG Plasma 50PA5500

Dabbi, That would indicate that your main board is bad and you should replace it.
Ideally you would cut a wire up and make it longer which would allow it to complete one loop of the test pattern.

[Dabbi]

Re: LG Plasma 50PA5500

okay I got a good bridge. and it ran all the way through the test sequence a few times. So yes it does appear to be the main board. I will swap that and hopefully it comes back to life. Thank you so much