Lg plasma tv no video has sound

[anthonyngan]

Hi,

First I'd like to thanks all members for the quality of their posts. I have used this site for some time now and always found pertinent information.

I'm working on my first plasma tv repair; the model no. is lg mu-42pz15. At first glance the power supply board seems ok. There is no visual signs of bad componants. However I only get va, vs, and vy voltage when the connector that links the power supply to the y sus (cn803) is unplugged. Does it mean that my y sus has a short?

Thanks

[tom66]

Re: Lg plasma tv no video has sound

If you get Vs, your Y sus, Z sus and power board are probably OK.

[anthonyngan]

Re: Lg plasma tv no video has sound

Thanks for the quick reply.

Does it mean that I should check the control board?
How is it that I only have any high voltage coming out of the power supply when cn803 is unplugged ( y sus connector on the PS)? I only have 5, 12 and 15 dc.

Your help is greatly appreciated.

Anthony Ngân

[tom66]

Re: Lg plasma tv no video has sound

Sorry, did not see the note about the voltages only present when Y sus disconnected; thought you meant when all were connected. Y sustain is bad then.

[anthonyngan]

Re: Lg plasma tv no video has sound

Great !
I'll try to swap the 2 IPMs.
Is there anyway to test them for shorts?

[tom66]

Re: Lg plasma tv no video has sound

Yes, post a picture of the rear underside of the Y-sustain, as the pins are labelled.

[anthonyngan]

Re: Lg plasma tv no video has sound

Here is the picture.

[tom66]

Re: Lg plasma tv no video has sound

OK, test from SUS_OUT to GND and Vs, then from Vs to GND.

All should read open on 200 ohm range.

[anthonyngan]

Re: Lg plasma tv no video has sound

Is it possible to have no resistance at all between all pairs?
Do I have to unsolder the ipms to test them?

[ricosavy]

Re: Lg plasma tv no video has sound

a quick visual check is to look under ipm with flash light between board and chip most time in my experience u can see that there are blown component under there or some type of crack.if u can not see this then do the short test multimeter.have u ever taken one off they are hard to unsolder unless u have the right tools.

[anthonyngan]

Re: Lg plasma tv no video has sound

Thanks!

I'll post again once I succeed in unsoldering the Ipms.

I found a tutorial on youtube : http://www.youtube.com/watch?v=Y8MNQYXw8E0

[anthonyngan]

Re: Lg plasma tv no video has sound

Alright!
I removed the ipms and found them to be shorted.
I found this site:http://www.pwrx.com/summary/IPM.aspx

However I'm having a hard time identifying the correct module. Can somebody help?

[tom66]

Re: Lg plasma tv no video has sound

Is there no part code on it? You won't find it on that website - you need ones like these: http://www.ebay.co.uk/itm/YPPD-J006A...item19c9f26818 However, you should be careful to match them exactly, as they are sometimes different.

[anthonyngan]

Re: Lg plasma tv no video has sound

Unfortunately, there is no bar code on all four of them. However, by looking at the images on google I was able to find an IPM 4921QP1002B which has the same amount of pins and fits on similar 42 inch plasma tv y-sus board from LG. However I could not find anything for my particular Y-SUS board : 6870QYE003C.

If not advised otherwise I'm going to go with that model number.
I found nemerous refurbished IPMs. Will they be as good as the new ones. I'm trying to avoid buying this part used since I beleive that they might had been used for some time...

Thanks!

[anthonyngan]

Re: Lg plasma tv no video has sound

Okay here's the update,

I received the IPMs I ordered. I was very excited, they came in fast from Hong Kong it only took two weeks. I tested them and found no shorts. I soldered everything and tested the TV. Unfortunately it wasn't working. But then I realized that I had forgotten to plug a connector on the y sustain board. I turned the TV on again, but still no image; I decided to do a voltage test. It turned out that I wasn't a getting any VS or VA, or VY voltage. I tried to unplug the connectors from the Y sustain board and do another test. As soon as I touched the VS a direct short was created. It melted the bottom case of the TV which was touched by the ground lead of the multimeter.
What did I do wrong?
The parts I replaced were definitely defective. Any help would be greatly appreciated.

[anthonyngan]

Re: Lg plasma tv no video has sound

Small update:
After a few tests I noticed that there's a buzz in one of the IPM's I just soldered. I'm going to check the joints again and see if I can see any problems.

[anthonyngan]

Re: Lg plasma tv no video has sound

Small update:
After a few tests I noticed that there's a new buzzing sound on the y-sus. The sound last one second and occurs everytin I push the main power switch. I'm going to check the joints again and see if I can see any problems.

[tom66]

Re: Lg plasma tv no video has sound

What test did you do on the Vs that caused the plastic case to melt? Did you accidentally have the meter on the 10A range?

[anthonyngan]

Re: Lg plasma tv no video has sound

Now that you mention it, I realized that this is what I did. I used an analog multimeter and had plug the positive lead in the 10 A.
I did not have the digital one that I was using before. I hope I didn't fry anything.
Anyway the short buzzing sound on ysus was occurring before. I'm going to try to find out what's causing it.

[tom66]

Re: Lg plasma tv no video has sound

Hopefully the PSU just went into protection mode, and will reset after a power cycle, they usually do.