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Old 05-29-2012, 05:42 PM   #1
Jahson
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Default 42lg3000-za No Picture but got sound

I got hold of a 42LG3000, it has sound but no picture. Ive removed all the boards, did a visual check & cant see anything wrong.

I like some help into how i can test the boards to see they are all working correct.

I did try get the schematic but cant get to download as the page wont load for me? It was working for me the other day when i downloaded a schematic from the same site.


I dont know were to put the probes on the board, an what the readings should be on my meter.

I have not got a camera, but i most def will be getting one, i know it is well needed in these types of situation.
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Old 05-30-2012, 05:33 AM   #2
selldoor
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Default Re: 42lg3000-za No Picture but got sound

Hi Pictures are really important as probably most of us will not have seen inside this set.
Did you try and download from here http://elektrotanya.com/lg_42lg3000_.../download.html you can only download two items per day unless registered and if you are impatient and double click then thats it. Try again switch off an adblockers and wait a minute after the page has loaded then click get manual near the bottom right hand side.
First sort of test might be to test for expected voltages on all the power supply output voltages. With it all connected up and switched on Meter on vDC200 black probe on chassis ground screw check each pin with red probe. report results like
CN1
Pin 1 24v actual 24.1
Pin 2 12v actual 11.5v
PSON actual 3.2v etc etc

Care do not touch heatsinks or primary side with body or probes. I have not got the sm downloaded but will do it later. May have a troubleshooting section you can work through and post the results.
My usual greeting is
Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
http://www.badcaps.net/forum/attachm...1&d=1290283049

http://www.badcaps.net/forum/attachm...7&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.
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Old 05-30-2012, 12:07 PM   #3
Jahson
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Default Re: 42lg3000-za No Picture but got sound

Thanks selldoor, had to go get a decent multimeter, when you say pin1, pin2 where do i look for these points.

Only thing i notice was i did a voltage check on the leads going to the inverter boards, they say 24.5v, the first 5 pins of that connecter (Both master & slave).

I was told it has no picture, it does have sound. Plugged in an checked.
About me im a real novice in electronics, hobbist.
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Old 05-30-2012, 12:18 PM   #4
selldoor
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Default Re: 42lg3000-za No Picture but got sound

I was hoping you would have the Service manual to work off.
There should be a connector to the main board list the voltages on that.
Is it labelled
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Old 05-30-2012, 12:31 PM   #5
Jahson
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Default Re: 42lg3000-za No Picture but got sound

Like were it says output:

5.2v - 6.5a
12v - 2.25a
16.5 - 1.3a
24v - 7.5a
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Old 05-30-2012, 12:33 PM   #6
Jahson
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Default Re: 42lg3000-za No Picture but got sound

did you get the schematic

Or do you mean like p204 Got 14 pins,
pin 1 is a blue wire should be 24v
pin 2 is grey 24v
pin 3 is grey 24v
pin 4 is grey 24v
pin 5 is grey 24v

Then the next 6 to 10 are GND
pin 11 =BR1
pin 12 =on/off
pin 13 =pwd dim
pin 14 =error

Does this make sense?

Last edited by Jahson; 05-30-2012 at 12:39 PM..
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Old 05-30-2012, 12:35 PM   #7
selldoor
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Default Re: 42lg3000-za No Picture but got sound

No - I think that must be in the middle of the board somewhere - remember I have never seen one of these. It will be a connector on the edge somewhere if the boards are still on the chassis you may not see what the voltages are as the labels, may be on the underside (if there are any)

No to schematic -no time to try- did you?
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Old 05-30-2012, 12:40 PM   #8
Jahson
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Default Re: 42lg3000-za No Picture but got sound

no label
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Old 05-30-2012, 12:47 PM   #9
selldoor
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Default Re: 42lg3000-za No Picture but got sound

Just to check - I dont mean a stuck on label I mean writing on the board silkscreened.
Not that it really matters - just start at one end and work along the pins- you might have to stick the redprobe in small holes along the side of the connector - it is sometimes quite difficult to get a connection
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Old 05-30-2012, 12:56 PM   #10
Jahson
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Default Re: 42lg3000-za No Picture but got sound

yea i did that, theres 3 connecters in total, 1 goes to master inverter, slave inverter, an the other to the av board if its called that the (board you connect scart, hmdi) this av connector slightly difference it has double row.
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Old 05-30-2012, 01:08 PM   #11
Jahson
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Default Re: 42lg3000-za No Picture but got sound

that connection for av board

pin 1 should be 16.5 meter reads 15.6
pin 2 gnd
pin 3 should be 12 meter reads 12.3
pin 4 gnd
pin 5 should be 5 meter reads 5.1
pin 6 should be 5 meter reads 5.1
pin 7 gnd
pin 8 gnd
pin 9 ACD
pin 10 on/off meter reads 2.9
pin 11 pwm dim meter reads 0
pin 12 n.c meter reads 0
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Old 06-01-2012, 12:44 PM   #12
Jahson
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Default Re: 42lg3000-za No Picture but got sound

selldoor does this make sense.
Dont know what i done but messed up my borrowed sealey mm20 meter.
tommorrow i have the pictures up, will be buying a camera.
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Old 06-01-2012, 03:34 PM   #13
selldoor
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Default Re: 42lg3000-za No Picture but got sound

The voltages dont look too bad 16.5 is is a bit low.

Dont know what i done but messed up my borrowed sealey mm20 meter.
The battery may be low or youve blown the fuse - have you got insructions?
Available here:
http://www.ccw-tools.com/uploads/ima...ns/MM20_V3.pdf
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Old 06-01-2012, 03:54 PM   #14
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Default Re: 42lg3000-za No Picture but got sound

With lights out in room does screen light up?

If so - T-con or main board, most likely T-con

If not - Inverter or PSU, most LG LCDs 42" and above integrate the inverter and PSU onto one board.
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Old 06-01-2012, 06:09 PM   #15
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Default Re: 42lg3000-za No Picture but got sound

hiya tom66 the meter is ok now many thanks yea i think it was the fuse.

With total darkness in room, cant see any lights on screen

Dont know if this helps but on start up the red standby light flashes 3 times?

I will mos def have a camera,and take some shots.
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Old 06-02-2012, 09:03 AM   #16
Jahson
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Smile Re: 42lg3000-za No Picture but got sound

Here the shots as promised
Attached Images
File Type: jpg PowerBoard.JPG (460.1 KB, 62 views)
File Type: jpg PSUreverse.JPG (631.3 KB, 48 views)
File Type: jpg AvBoard.JPG (429.0 KB, 39 views)
File Type: jpg AvReverse.JPG (478.1 KB, 34 views)
File Type: jpg MasterInverter.JPG (474.9 KB, 52 views)
File Type: jpg SlaveInverter.JPG (453.6 KB, 44 views)
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Old 06-02-2012, 09:16 AM   #17
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Default Re: 42lg3000-za No Picture but got sound

Too blurry to see anything really - does your camera have a macro mode?

My 42LC46 flashes the LED a few times when first turned on, seems normal.

I would suspect the inverter board.
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Old 06-02-2012, 10:01 AM   #18
vinceroger69
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Default Re: 42lg3000-za No Picture but got sound

in pic 6 by the bottom white connector to the left of it theres a white fuse does that test ok?
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Old 06-02-2012, 10:28 AM   #19
selldoor
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Default Re: 42lg3000-za No Picture but got sound

Same goes for Pic 5 White rectangle is probably a fuse.
Test with meter on Ohms one probe to each side of fuse- should be the same as touching probes together.



Probably need more light for photos - can you take outside for best natural light

Last edited by selldoor; 06-02-2012 at 10:36 AM.. Reason: light
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Old 06-02-2012, 11:04 AM   #20
Jahson
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Default Re: 42lg3000-za No Picture but got sound

sorry for the blurry images, brought a real cheap camera and cant return it? unless its faulty.

I think a soldering iron can fix that problem?
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