LG 50PC5D - Shuts Off

[capkid]

I'm working on an LG 50PC5D plasma TV that shuts off by itself. The power supply does not have any bulging caps, but I installed a cap kit as preventative maintenance. The TV stays on for a few minutes when it's cold, but it shuts off immediately if I turn it on when it's warm.

I didn't see any cold solder joints on the power supply, and hitting various areas of the power supply with cold spray had no effect. I moved on to the main board, and I was finally able to get the TV to stay on by repeatedly spraying what the service manual calls a "filter bead" with the cold spray. Based on like components on the board, this component seemed to test fine at 0.2 ohms. I replaced a few SMD caps near the filter bead that I originally thought were causing the issue, but that obviously didn't help.

Any ideas as to what could be causing the power supply to shut down? I was going to try replacing the filter bead if I could find a replacement, but I'm not sure whether it's the root cause. A red arrow in the upper-right portion of the attached pic points to the filter bead.

[tom66]

Re: LG 50PC5D - Shuts Off

The filter bead can get a crack and fail open circuit, so while it is failed try monitoring the voltage drop across it. In operation it should be near zero, when failed it should be high.

[martyparish]

Re: LG 50PC5D - Shuts Off

This probably isn't related but just in case, here is a rework that I used to repair an LG LCD.

The notes also show that one plasma was affected as well, although not your model.

I'm not sure if that filter bead you are referring to is the same as the components I removed and jumped, but they were labeled "Lxxx". They had four pins, but yours don't seem to have four from what I can see in the pic.

Anyhow, it's attached.

[capkid]

Re: LG 50PC5D - Shuts Off

This probably isn't related but just in case, here is a rework that I used to repair an LG LCD.

The notes also show that one plasma was affected as well, although not your model.

I'm not sure if that filter bead you are referring to is the same as the components I removed and jumped, but they were labeled "Lxxx". They had four pins, but yours don't seem to have four from what I can see in the pic.

Anyhow, it's attached.

Hmm, I'm not seeing any of the components mentioned. Anyway, I'll save this info for future use. Thanks.

The filter bead can get a crack and fail open circuit, so while it is failed try monitoring the voltage drop across it. In operation it should be near zero, when failed it should be high.

I just measured across the filter bead, and I only get 0.006V on both sides. Strange. Cold spray directly on that component continues to work to keep the TV running. For comparison's sake, I checked a few other filter beads, and they measure about 5V.

Edit: I just found an SMT cap next to the filter bead that measures 19V on one side and 0.006V on the other side. I'm thinking this might be my issue. From the service manual regarding this cap: C2012X7R105KFT 1uF 10% 25V X7

[capkid]

Re: LG 50PC5D - Shuts Off

Well, the 1uF cap I pulled was fine. I replaced it anyway, but it didn't make a difference. Added pic of the TV with the back off.

Edit: Ugh, I started trying just about anything to see if I could get a reaction from the TV. I spun the fan by hand just for grins, and it started running on its own to my surprise; it didn't dawn on me that the fan wasn't moving previously. I work on cars on occasion, so I think I had radiator fans on the brain, which aren't always moving. The TV's been on for about five minutes now. SMH

Has anyone tried repairing the fan, or would it be better to replace it? I'm going to see if cleaning it helps, and I may try some silicone spray parts of it.

[ohmmy]

Re: LG 50PC5D - Shuts Off

Set your multimeter to read amps and connect your probes across the filter bead without spraying it with cold air and turn the set on. If the tv stays running that's definitely your problem just replace it or maybe simply jump it with a wire. Though they're generally used for noise suppression so it might cause issues with set on doing it that way.

[capkid]

Re: LG 50PC5D - Shuts Off

Set your multimeter to read amps and connect your probes across the filter bead without spraying it with cold air and turn the set on. If the tv stays running that's definitely your problem just replace it or maybe simply jump it with a wire. Though they're generally used for noise suppression so it might cause issues with set on doing it that way.

No, it was the fan. I applied some silicone spray, and it's been running for a while now.