Lg 37LG6000 lcd tv

[oddbodd]

TV reported as taking longer and longer to turn on, over the course of about a year. TV power light now shows red, turning to white, and repeats, but no picture or sound.

Initial inspection showed no obvious blown caps, but looking with a magnifying glass, one or two show the slightest possibility of bulging [unless it's my eyes].

I've removed 4 SamYoung NXB 105C caps for testing...

C202 3300uf 10v
C203 3300uf 10v
C204 470uf 10v
C213 220uf 25v

...results below. They appear to be OK, though?

[oddbodd]

Re: Lg 37LG6000 lcd tv

Is the voltage loss within tolerance?

[oddbodd]

Re: Lg 37LG6000 lcd tv

Do the above caps look OK?

Should I be looking elsewhere?

[tom66]

Re: Lg 37LG6000 lcd tv

They look OK. I've never heard of "voltage loss" being a capacitor parameter.

[snipersquad100]

Re: Lg 37LG6000 lcd tv

Sorry this is not useful but I was wondering why the pcb says "Bottom" on the top?

[tom66]

Re: Lg 37LG6000 lcd tv

These sets have two power boards I believe, split in half. Not sure why.

[snipersquad100]

Re: Lg 37LG6000 lcd tv

Mystery solved, thank you.

[selldoor]

Re: Lg 37LG6000 lcd tv

Perhaps try and locate the start up cap - usually a small one often 50v on the primary side
There are a lot on these two boards so couldnt even guess - perhaps Tom knows?

[oddbodd]

Re: Lg 37LG6000 lcd tv

There are six 50v caps on this board.

C206 10uf
C501 10uf
C512 47uf
C510 22uf
C511 22uf
C508 10uf

I'll have a look at the other board later.

[selldoor]

Re: Lg 37LG6000 lcd tv

Could be any 47uf is a common value for it - I cant tell which is which - pictures are quite good but as you say not enough light - I have the same problem here.
The startup usually connects to a pin on the controller chip - usually 8legs cant see one on top so underneath?.

It also has to be in the primary section of the board - that at least is marked on these boards

[vinceroger69]

Re: Lg 37LG6000 lcd tv

what makes it worse these use 2 psu s is the main one picture 5 or 7 seven would be my guess and i would start with the small caps by the heat sinks remove and test or just replace them.

[selldoor]

Re: Lg 37LG6000 lcd tv

Tom has a sm which has some ps detail tht might help.
Also need to check voltages at connectors to see what you have got.
Last few pages of schematic might help.

[don81]

Re: Lg 37LG6000 lcd tv

Might want to check caps around micro,on main. mostly smd caps small voltage 6.3 or diodes for leakage Have found some leaky diodes on lg sets

Hope all goes well for you

Don81

[oddbodd]

Re: Lg 37LG6000 lcd tv

Thanks guys. That's given me a few things to check, tomorrow.

[budm]

Re: Lg 37LG6000 lcd tv

You already try heating the caps with hair dryer to see if the TV start up faster and normal?

[oddbodd]

Re: Lg 37LG6000 lcd tv

No, I've not heard of the hair dryer trick. Another use for that gadget, apart from drying paint quickly!

OK, some more pics.

The top board, where I've located a 50v 20uf cap at C113. It's quite close to a heat sink on the primary section, with white gloop on it.

Removed and tested. ESR = 1.6.

Bad?

[tom66]

Re: Lg 37LG6000 lcd tv

Probably OK.

[oddbodd]

Re: Lg 37LG6000 lcd tv

OK, I'll check some others.

[selldoor]

Re: Lg 37LG6000 lcd tv

Told somebody off the other day for not dusting their boards - how can you check for cold solder joints if you dont? It also makes a nice blanket preventing air from cooling components.
While I am having a rant, I think the idea is you should look up the data sheets for the caps you are testing, not just ask if we think they are bad.

[oddbodd]

Re: Lg 37LG6000 lcd tv

Sorry about that, but as you probably realise, I'm just learning all this and there's a lot to take in. I'm not sure that I'd recognise a cold solder joint yet, unless it was blatantly obvious, anyway.

So... I've now tested all the caps on the top board. The 25v and 35v caps seem OK.

C111 is a Sam Young 105C NHA 450v 10uF cap. I tested it after desoldering and it was reading 11.01uF and ESR = 1.6.

But as it's cooled, it now reads 10.69uF and ESR = 5.9.

There aren't any values for ESR in the NHA datasheet.