Emerson LC320EM2 back lights on but no picture

[budm]

Re: Emerson LC320EM2 back lights on but no picture

Can we get better focused pictures of the main board, especially around the LVDS connector? There must be switch MOSFET that supplies the voltage to the T-CON when the processor send the signal to turn on that MOSFET.

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

tom66
On 200k ohm scale it starts at around 39 and climbs up to and stops at 73.6 on both ends of the fuse.

budm
My old shaky hands aren't the best at taking pictures, but hopefully this one is fairly clear.

[budm]

Re: Emerson LC320EM2 back lights on but no picture

Never mind, looking at it wrong, I will post back later.

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

Positive lead on + of cap C3831 and negative lead on each pin of IC3004 gave a reading of 9.74 ohm.

IC3004 has 330 S3 marked on top.

[tom66]

Re: Emerson LC320EM2 back lights on but no picture

What is the part # of IC3010?

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

I cant hardly see the numbers but the best I can tell it says
M2305SDS
C2456328
MPSC17

[tom66]

Re: Emerson LC320EM2 back lights on but no picture

I suspect it's an MP2305 device which is broadly similar to the MP2307. Datasheet here: http://www.ic37.com/MPS/MP2307_datasheet_5331544/

Check pin 2 (supply voltage), pin 7 (enable voltage) and pin 8 (softstart voltage)

Expect for working CPU but bad converter IC:
Supply >4.7V
Enable >2V
Softstart > 0.925V

Expected for bad CPU/firmware issue/other fault:
Supply >4.7V
Enable <1V

Expected for PSU problem/fuse/etc:
Supply <4.7V

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

Oops
I am embarrassed to admit it, but I made a rookie mistake. My test lead slipped and I accidentally touched an adjoining pin and shorted the TV.

It didn't blow the PSU fuse but there was a squealing noise coming from the PSU. I immediately unplugged the set.

I unplugged the power cable going to the main board and plugged the TV back in and there was no squealing so I'm thinking the damage was done to the main board only.

Do you think the problem was leaning towards the main board?
If so I can get a replacement on ebay for around $14

If you all think it's likely to be a bad t-con (which isn't replaceable on this TV) I'll put it back together and save it for parts.

grrr I could kick myself for being so clumsy

thanks

[tom66]

Re: Emerson LC320EM2 back lights on but no picture

Are the original symptoms still present? It's possible you did not damage anything. I am currently leaning towards the main board, the tests will prove it either way.

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

The symptoms are different now.
Before the slip I had back lights and sound, but no picture.
Now the back lights don't come on at all and there is a squealing noise coming from the PSU.

[tom66]

Re: Emerson LC320EM2 back lights on but no picture

Oh, OK, in which case yes you probably did do damage. I guess try replacing the main board then.

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

ok thanks for your help.
I will post back when I get the replacement board.

thanks again everyone

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

I received my replacement main board today and unfortunately it didn't fix the TV.
It's back to the original problem. The TV turns on and the back lights light up, but no picture.

After pressing the power button the red power light blinks 19 times before the back lights turn on. Not sure if that means anything or not. I googled it and didn't find any info.

So I'm guessing the problem is likely the T-Con? and the TV is not repairable?
Any other things I could try or is my best bet just to part it out?

thanks

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

bump

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

bump and happy memorial weekend everyone

[Dgtech]

Re: Emerson LC320EM2 back lights on but no picture

It's very easy to find a T-con board for this set. Just search in ebay "LC320EM2" and "t-con". You will find at least one there. Or just try to search for the model numbers on the board itself. There are a few different versions of this board so...I don't know how they differ or even if one will work for the other.

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

I forgot to post the measurements of IC3010.

tom66
IC3010
Pin 2. 21.4v
Pin 7. 3.2v
Pin 8. 3.6v
if i measured the right pins (see pic)

Dgtech
Unfortunately I don't think the T-Con on my TV is replaceable. It seems to be built into the board on the top of the TV.

thanks

[Dgtech]

Re: Emerson LC320EM2 back lights on but no picture

wow, yeah, you're right. That's a total different set than I've ever worked on.

[Gorrillasnot]

Re: Emerson LC320EM2 back lights on but no picture

do u all think its something in the power supply or t-con?

thanks

[tom66]

Re: Emerson LC320EM2 back lights on but no picture

OK what voltage do you measure on the pads of C3047 (no component is placed here, it is a blank spot.) It is just above the IC.