Lg 42pc3d-ue

[Peter9DO]

Hello everyone! I'm new to the forum however I think you will be seeing a lot of me! I have a repair business and I love chatting with people in my field, seeing that I work from home and don't get out enough! Currently I started working on TVs to venture into something other than computers, ipods, Playstations and all that other good stuff. I find that LCDs are fairly simple and really don't mind working on them. Then I bought some broken Plasma TV and they are all sitting there still broken a month latter. I did some reading, purchased some tools and here we go!

I have this LG 42PC3D-UE here, I have check the fuses and all is well! I had a bad cap at C275 swapped it out with a "new, used one" I have tested all the other caps on the power supply with my Atlas ESR70+ and nothing else seems to be an issue. Put it all back together and hit the power button and what do I get a flash of light on the screen and back to NOTHING! When I turn on the TV with the back panel removed, I Notice as soon as the green light on the main board lights up everything turns off. Now does the power go threw the main board and send signal to the x and y-sus? The SMT processor on main board is almost what I'm thinking it is, I was going to give it a re-flow to see if that would get it going but before I put the time in to re-flow and poss re-ball the chip I wanted to make sure that the issue is with the main board and not the Y-sus or X-sus or even the buffers for that matter. I should have a oscilloscope and function generator by this weekend, however I really don't know how to use it. I figured I would give myself some lessons and maybe test it out on this TV. Does anyone have any suggestions on what the issue may be. I have went threw the post on this model and I have noticed that one of the users claimed that, it's common for the Y-Sus to go bad on this model TV. At this point I'm ready just to swap parts out and be done with it but on the other hand I have a new toy on the way and want to play with it! Any help would really help! Thanks guys!

Thank you,
Pete

[PlainBill]

Re: Lg 42pc3d-ue

This family of TVs has a history of defective Y and Z sustain boards.

PlainBill

[Peter9DO]

Re: Lg 42pc3d-ue

Yea, I noticed that was mentioned on a couple of different threads on this forum. I also noticed you were dominating the threads when it comes to this model T.V. (to be honest I'm very happy that you have commented on mine). So, do you think I should just put it back together and check the Y-sus and the X-sus one at a time to see how if there is any difference in what the T.V. is doing? My only beef with it is as soon as that green light comes on, on the main board the T.V. shuts off. So I want to believe that it has something to do with the CPU on the main board. But again Plasmas are new to me. What rout would you take to start? I just don't want to nickle and dime this thing but then again, I guess I won't learn until I start working out the kinks one at a time. By the way, thank you for your post!!!!!!!

[PlainBill]

Re: Lg 42pc3d-ue

Yea, I noticed that was mentioned on a couple of different threads on this forum. I also noticed you were dominating the threads when it comes to this model T.V. (to be honest I'm very happy that you have commented on mine). So, do you think I should just put it back together and check the Y-sus and the X-sus one at a time to see how if there is any difference in what the T.V. is doing? My only beef with it is as soon as that green light comes on, on the main board the T.V. shuts off. So I want to believe that it has something to do with the CPU on the main board. But again Plasmas are new to me. What rout would you take to start? I just don't want to nickle and dime this thing but then again, I guess I won't learn until I start working out the kinks one at a time. By the way, thank you for your post!!!!!!!

When a hybrid shorts there are three possible outcomes.

1. The hybrid shorts and the current surge blows an internal link, so it no longer loads the supply.
2. The hybrid short blows a fuse on the sustain.
3. The hybrid shorts and overloads the power supply.

I have seen all three of these scenarios; on one, outcome 3 changed to outcome 2 as I was negotiating with the owner.

The quick and easy test is to disconnect the power cable to the each sustain in turn. If the TV stays on with a particular sustain disconnected, that sustain is bad. If it shuts down unless both are disconnected, both might be bad, but I would suspect the power supply. If it shuts down even if both are disconnected, I would suspect the power supply unless all voltages were correct before it shut down..

PlainBill

[Peter9DO]

Re: Lg 42pc3d-ue

Okay, so what I'll do is put this "new" used cap in at C275. Put everything back together and see what I get from checking the sustains. I will let you know what I come up with.

Thanks again,
Pete

[Peter9DO]

Re: Lg 42pc3d-ue

Sorry, it took a couple of days to get back! I have been painting a bedroom in my house for my baby boy I'm expecting in a couple of months!

Anyways, this is what I got:

Replaced capacitor @ C275 (10v 1000uf)

I checked the Voltage on Vs and Va :
Vs Reading: 184.5v (factory specs:185v) shouldn't be an issue!
Va Reading: 59.9v (factory specs: 60v) Again not an issue!

With all the boards hook up in the TV; the TV will power on and shut off and continue the cycle of turning on and shutting off until the power wire is pulled. The screen will also flash a white color, right before it powers off.

I have unplugged the zsus: same issue as above.

I have unplugged the ysus: same issue as above.

I have unplugged the zsus and the cable at P800: now the TV will stay on but I'm getting a little red dust moving around on screen.

I then tested all the pins at P800 everything was at the proper voltage.

NOW! I'm really confused! lol! I think there is something wrong with the zsus and I'm just going to replace it. Any suggestions?

[PlainBill]

Re: Lg 42pc3d-ue

Sorry, it took a couple of days to get back! I have been painting a bedroom in my house for my baby boy I'm expecting in a couple of months!

Anyways, this is what I got:

Replaced capacitor @ C275 (10v 1000uf)

I checked the Voltage on Vs and Va :
Vs Reading: 184.5v (factory specs:185v) shouldn't be an issue!
Va Reading: 59.9v (factory specs: 60v) Again not an issue!

With all the boards hook up in the TV; the TV will power on and shut off and continue the cycle of turning on and shutting off until the power wire is pulled. The screen will also flash a white color, right before it powers off.

I have unplugged the zsus: same issue as above.

I have unplugged the ysus: same issue as above.

I have unplugged the zsus and the cable at P800: now the TV will stay on but I'm getting a little red dust moving around on screen.

I then tested all the pins at P800 everything was at the proper voltage.

NOW! I'm really confused! lol! I think there is something wrong with the zsus and I'm just going to replace it. Any suggestions?

I don't have the connectors memorized, and don't feel like looking it up. Where is P800?

PlainBill

[Peter9DO]

Re: Lg 42pc3d-ue

It's the first cable the goes from the power supply to the AV board (out of the 3 connectors that go from the power supply to the AV board)

It's a 13 pin connector, below is the labels in order from left to right:
3.30N , DET , 6V , NC , GND , 5-5V , M5V-ON , 5V-D , VS-ON , GND , 5-5V , RL-ON , AC-D

[Peter9DO]

Re: Lg 42pc3d-ue

Will a picture help?

[PlainBill]

Re: Lg 42pc3d-ue

Will a picture help?

Yes. I've got a service manual, but I can't find P800 on the schematic of the main board. What connector does it go to on the main board?

PlainBill

[Peter9DO]

Re: Lg 42pc3d-ue

So the first image is of the power supply where the red line is, is the location of P800. The 2nd image will brings it in a little closer.

The 3rd picture is of the AV board again the red line shows where the P800 is. 4th Image brings you in a little closer.

I also have the service manual on this TV and I was not able to figure out why it's doing what it's doing other than the z-sus and maybe the AV board is bad.

Again, thank you for the help!

[PlainBill]

Re: Lg 42pc3d-ue

So the first image is of the power supply where the red line is, is the location of P800. The 2nd image will brings it in a little closer.

The 3rd picture is of the AV board again the red line shows where the P800 is. 4th Image brings you in a little closer.

I also have the service manual on this TV and I was not able to figure out why it's doing what it's doing other than the z-sus and maybe the AV board is bad.

Again, thank you for the help!

Thanks for the identification. I'll see if I can find P4004 on the schematic and update the thread.

EDIT: OK, I was having a senior moment. This time I found the connector. As closely as I can determine, the main board is turning the power supply off. My experience with this chassis was the power supply would work even if the Z-Sustain was disconnected. I agree, you may have a bad Z-sustain and a bad signal board.
PlainBill

[Peter9DO]

Re: Lg 42pc3d-ue

GREAT! Well, not really! But it's great that you concur!