LG 37LC2D No Sound, and No Channels

[whitemus]

I have an LG 37LC2D that has no sound and picks up no channels. The HDMI works, but no sound from it either. The picture is great, and all the menu functions are working well. Any ideas on what could cause both of these to stop working? Any help is much appreciated!

[tom66]

Re: LG 37LC2D No Sound, and No Channels

Seen it before - low 3.4V on PSU. Mine had loss of sound (everything), no Freeview channels (always "Weak signal"), intermittent HDMI, and intermittent RC control and side-buttons. Everything else worked so it had to be something common to these.

My fix was to replace the PSU (cost £30) because I was a bit stupid and burnt out a few other compoennts but you might be able to replace a bad cap which sometimes goes bad.

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

None of the caps look bad, so should I just replace all of them on the PSU?

[tom66]

Re: LG 37LC2D No Sound, and No Channels

First, do you have a digital multimeter?

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

Yes, I have one.

[tom66]

Re: LG 37LC2D No Sound, and No Channels

Good... Can you post some pictures of the power supply, especially around the connectors going to the main boards. It's been a few months since I fixed mine so I can't remember where the 3.4V is output, but it is labelled.

BTW, are you in the UK or US or another country? The US version of the 37LC2D is very different to the UK version, although the PSU is the same.

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

I'm in the US. I'll post some pics here in a min.

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

Here are two views of it. With and without the connectors.

[tom66]

Re: LG 37LC2D No Sound, and No Channels

Thanks for those nice, clear pictures.

I've highlighted in RED some test points for 3.4V. (There are several.) I've also highlighted a connector in green.

Please set your meter to DC 20V if it is manually ranging, otherwise if it is autoranging use normal DC volts.

Then, place the black probe in the chassis of the TV.

Plug the TV in and put it into standby mode.

Check the 3.4V voltage on the red pins using the red probe. You should get from 3.2V to 3.4V.

Then turn it on (exit standby mode) and re-test 3.4V.

Turn off and unplug the TV.

Then, unplug the green connector which provides power to some audio processing logic, which is the most power hungry part of this TV.

Repeat the above 3.4V test with this connector unplugged; if 3.4V substantially rises the problem is probably with the 3.4V supply.

Note the above test MAY only be applicable for the UK version as that has a separate AV board with audio and a HDMI/video/scaler/DVB-T board.

[retiredcaps]

Re: LG 37LC2D No Sound, and No Channels

None of the caps look bad, so should I just replace all of them on the PSU?

If those green caps are Samxon GF series, they are a known bad series. I'm not saying they are bad in your TV, but something to keep in mind.

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

Okay, I tested with the power on, and it reads 3.41. With the "green" unplugged, it reads 3.46. I do not have the remote to try standby mode. The green caps are definitely Samxon GF series caps.

[tom66]

Re: LG 37LC2D No Sound, and No Channels

Hmm. That is strange, because a low 3.4V voltage would normally cause the problem, as it has been on my set and a few other users.

There is also a 19V supply on this board and a 6V supply. Both use a similar circuit to the 3.4V so potentially they could go bad too. Can you please test both of these and see if they are reasonably close?

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

The connector on the left was at 3.31, and the connector in the middle was at 3.41. I only tested the 3.4 points. Also the speakers have been making a loud static sound just since I've been testing the power board.

[tom66]

Re: LG 37LC2D No Sound, and No Channels

That is another symptom of the low 3.4V (crackling sound), but it's possible the US version is different, maybe moving the 3.4V power to the main boards.

On the connector can you see the markings for 6V and 19V?

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

Yes, I see those.

[tom66]

Re: LG 37LC2D No Sound, and No Channels

Yes, I see those.

Can you check them and see if the voltages are close to the labels?

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

All the points were reading
6v-11.78
12v-11.83
19v-18.8

[tom66]

Re: LG 37LC2D No Sound, and No Channels

That is a very high 6V; it could be causing a problem, though I'd normally expect something REALLY bad to happen if it was nearly double the voltage. Like smoke and flames from parts . Double and triple check that is reading correctly.

[whitemus]

Re: LG 37LC2D No Sound, and No Channels

Its still reading at 11.78 for the 6v. I unplugged the middle connection, and then it dropped to 10.98, but that is still almost double. Its crazy because the tv works as far as picture goes. It just has no sound nor channels.

[tom66]

Re: LG 37LC2D No Sound, and No Channels

When you unplug that connection does 12V drop similarly?