LG 42LC7D-UB power problem.

[dietzcj]

Re: LG 42LC7D-UB power problem.

Here is a blown up photo of the whole green side board

[dietzcj]

Re: LG 42LC7D-UB power problem.

I used CapXon and Su'scon.
2200 uf, @ 10 V

[tom66]

Re: LG 42LC7D-UB power problem.

I used CapXon and Su'scon.
2200 uf, @ 10 V

No way... Those will be useless. *Especially* if you removed them from something old. Buy some Rubycon YXF, for $4 or less you can get 4.

[dietzcj]

Re: LG 42LC7D-UB power problem.

Tom66,
I doubt that these capacitors are bad. I bought them new on ebay. And I do not doubt that Rubicons are better, but it is besides the point, the power supply is acting with the exact same symptoms as before and after the capacitor replacement.

Even if I did replace them with whatever name brand capacitors, I think I would still have an overheating problem.
Your board had bad capacitors (bulging) but I think I would like to get to the source of the problem before going out and get 2 dozen or so capacitors and just blanket replacing them all.
Thanks for the advice though, someone with that problem could read this thread.

[tom66]

Re: LG 42LC7D-UB power problem.

Tom66,
I doubt that these capacitors are bad. I bought them new on ebay. And I do not doubt that Rubicons are better, but it is besides the point, the power supply is acting with the exact same symptoms as before and after the capacitor replacement.

Even if I did replace them with whatever name brand capacitors, I think I would still have an overheating problem.
Your board had bad capacitors (bulging) but I think I would like to get to the source of the problem before going out and get 2 dozen or so capacitors and just blanket replacing them all.
Thanks for the advice though, someone with that problem could read this thread.

The problem is, Samwha caps are at least *somewhat* good; they'll pass for a year or two. CapXon and Su'scon are complete trash - basically replace them on sight, even if not bulging. If this TV does work, you'll be replacing them in a year or so, anyway...

Overheating isn't likely, but many electrolytic caps are temperature dependent. Some work better, some work worse, at higher temperatures. Another possible issue is a bad/cold solder joint. On a 32" Goodmans TV, I found the protection ckt was preventing the supply from starting up in certain conditions.

[PlainBill]

Re: LG 42LC7D-UB power problem.

Awww, crud!!! There are two separate control inputs on P201. There is the On/Off input which you have overridden, but the last pin on the other end of P201 is '3.4V ON'. Does that change state when the TV shuts down?

PlainBill

[dietzcj]

Re: LG 42LC7D-UB power problem.

The TV does power up for a bit and works for about 8 - 10 min.
Then shuts off completely.

[dietzcj]

Re: LG 42LC7D-UB power problem.

Sorry PlainBill the last post was not an answer to your question.

Tom66 I have ordered 12 2200uf, 10V RUBYCON caps....Just based on your affinity for that brand name.

Plainbill, do I need to test with the batter trick as well ?

[PlainBill]

Re: LG 42LC7D-UB power problem.

Sorry PlainBill the last post was not an answer to your question.

Tom66 I have ordered 12 2200uf, 10V RUBYCON caps....Just based on your affinity for that brand name.

Plainbill, do I need to test with the batter trick as well ?

Yes, I'd suggest that as well. We really want to establish which board is causing the failure. The only way to do that is to take control of the power supply away from the main board.

I've been racking my brains trying to figure out why they would have TWO On / Off control lines. So far the only answer I come up with is '????'

PlainBill

[dietzcj]

Re: LG 42LC7D-UB power problem.

Okay same result.
With both 3.4 bypassed with the batteries (which I think is genius idea) the tv does shut off and I get a .09 reading instead of 3.4.
So the power supply is shutting down after a period of time.

[PlainBill]

Re: LG 42LC7D-UB power problem.

Okay same result.
With both 3.4 bypassed with the batteries (which I think is genius idea) the tv does shut off and I get a .09 reading instead of 3.4.
So the power supply is shutting down after a period of time.

Correct. Did you check the other output voltages?

I see the circuit that is producing the 3.4 volts, but the #%T%@@%!!! picture doesn't show enough detail to even let me be sure of the numbers, but it looks like U202 is one of them.

PlainBill

[tom66]

Re: LG 42LC7D-UB power problem.

Sorry PlainBill the last post was not an answer to your question.

Tom66 I have ordered 12 2200uf, 10V RUBYCON caps....Just based on your affinity for that brand name.

Plainbill, do I need to test with the batter trick as well ?

I'm not a particular fan of any electrolytic capacitor (they are all necessary evils), but at the moment, the only ones I would recommend (for low ESR applications) would be Panasonic, Rubycon, UCC/NCC and maybe Samxon or Samwha for a day or two. Capacitor plague mostly affected the less well known brands, although caps still go bad without being affected by cap plague. I use general purpose cheapies in places like audio coupling and voltage regulators because they don't matter that much.

[dietzcj]

Re: LG 42LC7D-UB power problem.

PlainBill,
Yes all other voltages are Okay, just the 3.4 is low or not even registering.

[PlainBill]

Re: LG 42LC7D-UB power problem.

PlainBill,
Yes all other voltages are Okay, just the 3.4 is low or not even registering.

OK, the problem is probably in the area of the two transistors and the IC to the right of the output connector in the view of the green side of the board.

Also, to continue of the subject of replacement caps, look at the pictures in this auction.

PlainBill

[dietzcj]

Re: LG 42LC7D-UB power problem.

Is it your reccomendation that I just replace the caps ?

Also what transistors and IC do i need to replace ?

[tom66]

Re: LG 42LC7D-UB power problem.

Is it your reccomendation that I just replace the caps ?

Also what transistors and IC do i need to replace ?

Can you read the number on the IC. I believe, from when I was repairing my TV, that it is a synchronous buck converter. It takes 5V and outputs 3.3V (or 3.4V.)

Which caps are you now using?

[dietzcj]

Re: LG 42LC7D-UB power problem.

the D201 location ?

[dietzcj]

Re: LG 42LC7D-UB power problem.

D201 location
N7B (or 8)
ch20A20
>|--|< 156

[dietzcj]

Re: LG 42LC7D-UB power problem.

fch20A20

[tom66]

Re: LG 42LC7D-UB power problem.

No, this one.

Do you have an oscilloscope? I'm going to guess no... but I've been surprised before.