LG 32LC2D-EC - NO SOUND (and other issues)

[tmcw]

Got this TV yesterday, guy said it was an ex-display set, and that the sound wasn't working. Took it home, and when I managed to tune in some terrestrial channels, at first the sound was mainly static, but I could hear some speech behind it. Through a bit of switching on and off, and messing about with the extensive sound options, at one point the sound was coming in perfectly, but after switching on and off again, the sound is now completely dead.

Picture and backlight seem to be good though, so some hope at least...

So I take off the back and instantly I can see the four 1000uf (25V/35V) caps at the top (near connections going to inverter) are domed. Gold and black Sanwha VA. When I took a couple of them off, I notice that they are 130dC caps, bulging top and bottom.

Q: Would I get away with some 105dC FM's? Don't have any 130dC's to hand, and they're probably not the problem with the sound at the moment, are they?

Anyway, I've read a few of the other threads regarding similar sets, with similar issues, so turning my attention to the 3 connectors going to the av/jack boards. None of the caps around there are obviously bloaded, and are a mixture of Samxon (GF M) and (KMOD UNA/UOA) and Sanwha (RD). I measured the voltages coming off the connectors, and am getting the following (board marking - actual), I've left out any GNDs:

P201:
3.4V - 2V
6V - 3.25V
DIM - 3.3V
5V - 5.1V
BRI - 3.25V
ERR - mV
I(?) - 4.9V
5V - 5.1V
ON - 3.2V
ACD - 5.1V

P202:
12V - 11.85V
3.4V - 3.5V
6V - 3.3V
19V - 19.15V
19V - 19.15V

P203:
12V - 11.85V
12V - 11.85V
6V - 3.3V
6V - 3.3V
3.4V - 3.5V
3.4V - 3.5V

Some other details on the powerboard:
PCB: 687(?)9D0006B REV 1.1
PSU: 6709900016 A
FN6112B016A2164

So, where to go from here? Replace the 8 Samxon and Sanwha caps anyway, retest, and take it from there? Or can it be narrowed down further, it looks like it only the 6V that's considerably out at the moment. Is it likely to be a cap issue, or a power transistor problem?

Other details: RC seems to be working fine. There may be an issue with the tuner, first couple of times I tried getting DVB-T channels, it couldn't find them, but did after the set was on a while. I could get the current analogue channels, but this morning, the set can't seem to find them. Minor issues since analogue will be switched off on October, and the DVB-T tuner isn't H.264 capable anyway, so the set will be used for SCART and HDMI anyway.

[ben7]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Replace the caps and see what has changed, sometimes (worst cases) when the capacitors go bad other circuits can get fried. Or, bad cap sometimes make other circuits seem fried, but they are really not fried.

Edit: Also, the 3.4v on P201 looks low!

[tmcw]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Success!!

I began by replacing one at a time, to see which might be the problem, but with 10 caps to change (12 minus 2, as I don't have any 3300uF caps), after about 5 or 6, I just replaced the rest of them in one go, and all seems good with the unit.

The sound is working great, and there were issues with the tuner (both digital and analogue), but both seem to be functioning correctly too.

The 6V is now a nice 6.12V, all other voltages seem to be the same as they were before I began replacing caps. Even the labeled 3.4V is still giving 2V, but I forgot to say that that label also says "ON" below it, so maybe it's just a signal line?

So just a couple of questions regarding the caps I replaced...

The 4 black and gold caps (1000uF/25V,35V) were 130dC, but I only have 105dC FCs, will they do? Any kits I've seen are all 105dC caps. If anyone has worked on this series of PSU before, were they 105 or 130 degrees Celcius caps?

One of the other caps was a 470uF/10V, but I only had a 50V, will it be ok, it's not too high, that it might cause problems down the line? It's a bit fatter than the previous one, so a bit closer to the power transistor nearby (to the right of the middle orange component in the picture above), maybe I'll change it when I get another batch of caps.

[selldoor]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Hi - the caps you replaced, are these all on the power supply. I have a set and picture works great but the sound is quite distorted and wondered if it was caps on the mainboard audio amplifier section?

[tmcw]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Yes, all caps replaced are on the power supply board. I didn't touch any of the other boards.

If your sound is distorted (like static) on terrestrial channels, check to make sure you have the correct "SYSTEM" selected in the tuning section. When I put the power board back for the last time and checked the channels, whilst I was happy to hear a difference (there was now sound), it was all distorted, but when I changed the system to "I" (other options like DK, BG and L, IIRC), the sound was crystal clear. Of course, if it's distorted on AV inputs as well, then this won't apply.

It seems to me that the 6V is crucial for the sound, if you're not getting it, then you might need to check all 12 caps on that side of the power board (maybe you can omit the 2 3300uF caps, I think they are associated with the 19V section).

I wish I'd been a bit more systematic in replacing the caps, but it was taking too long, and it looked like I was getting nowhere. I really need to get an ESR meter. And schematics for the board would be nice too, a few other places I've read were trying to find them, but couldn't.

[selldoor]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Thanks- Ill try some of those ideas.

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Same chassis as my 37LC2D. Mine had no sound too - low 3.4V line measuring 1.3V. New PSU fixed it...

[tmcw]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Same chassis as my 37LC2D. Mine had no sound too - low 3.4V line measuring 1.3V. New PSU fixed it...

The 3.4V pin on the P202 and P203 connectors are ok, but the "3.4V ON" pin on P201 is still 2V - would this be ok? Set is working ok as far as I can tell, so what might this connection be used for?

Also, any advice on the 105dC vs 130dC caps? Which does yours (or anyone else with a similar PS board) have? Since these caps are involved in supplying the inverter and placed directly above a transformer (but close to a back cover vent), maybe they need the extra temp caps.

Also, on the large mainboard, I notice that there are 4 LEDs illuminated, but there seems to be another LED that isn't. Should all 5 of them be lit up?

[tmcw]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Just a quick post to upload a photo with the locations of the LEDs on the mainboard, the 4 illuminated LEDs can be seen, the other LED which isn't (LED300) is to the left of the connector, boxed in red.

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

That other LED on mine only lit up when 3.4V was okay.

[Twinky]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Howdi!

I've just been given one of these sets with a distorted sound syndrone.

the DVB-T tuner isn't H.264 capable anyway, so the set will be used for SCART and HDMI anyway.

Just wondered what that bit meant? - Reason I ask is that to me that sounds like it may not work / receive TV channels on Freeview here in the UK?

I've got the thing apart and can see straight away that C208 on the PSU is bulging and was just wondering if I need to worry about replacing the others or just go for the visibly duff one?

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

The 37LC7D receives freeview. Not sure about the 32LC2D but it's likely a similar chassis.

[Twinky]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Hi

Sorry yes I have the 37 (just realised this thread is about a 32 doh!)

Anyway I've replaced a 1000uF 16V 105degree cap on the psu that was clearly bulging but no difference.

Any ideas?

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

3.4V is good or bad?

[Twinky]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

I can test that with the connector plug taken off yes?

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

It should be connected to the main board and power supply, not disconnected -- you can touch your probe on the tiny exposed metal around the pin to test.

[Twinky]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

Hang on, which 3.4V are you talking about? - I thought you meant on the PSU itself? - That being the case I can't access the metal contact with the plug in place ~)

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

3.4V on PSU. You should see a tiny bit of metal exposed when cable is plugged in.

[Twinky]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

2V on P201, 3.4 on P202 and 3.4 on P203 (I see what you meant about the metal now - in the top of the connector with the wire!).

Also my 5th LED isn't lit up just like tmcw's TV

PSU buzzes very slightly but nothing I'd call alarming..

[tom66]

Re: LG 32LC2D-EC - NO SOUND (and other issues)

What is the marking on the pin reading 2V? Is it 3.4V_ON?