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Old 07-17-2012, 01:44 PM   #1
danjcarr1
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Default Faulty 42LG3000 Help!

Hi all,

I have a faulty 42LG3000 TV.

The fault is that when the set is powered on it comes on and the image flashes on the screen for a second if that, then the display goes black although the sound can still be heard.

Has anyone ever encounted this fault?

Any advice would be greatly appreciated.

Dan
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Old 07-17-2012, 01:46 PM   #2
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Default Re: Faulty 42LG3000 Help!

It sounds like 2 seconds to black; quite a common issue in fact. I just fixed a TV with this fault. A good start would be to post pictures of the insides of your TV.
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Old 07-17-2012, 01:49 PM   #3
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Default Re: Faulty 42LG3000 Help!

Ok thanks Tom, I will dig out the camera and post some pictures
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Old 07-18-2012, 07:28 AM   #4
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Default Re: Faulty 42LG3000 Help!

Please find an attached image of my set minua psu

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Old 07-18-2012, 07:29 AM   #5
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Default Re: Faulty 42LG3000 Help!

On each side of the screen there is an inverter.

Can you please take a closer picture of each inverter. Thanks.
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Old 07-18-2012, 07:30 AM   #6
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Default Re: Faulty 42LG3000 Help!

I have repaired tvs in the past and there is nothing obvious to the eye that i can see.
Also my fault sounds as if it may well be the two seconds to black that you mentioned. You can see the full screen image once first turned off then it goes black and only the sound can be heard.
Dan
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Old 07-18-2012, 07:40 AM   #7
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Default Re: Faulty 42LG3000 Help!

Master - VIT71053.54 LOGAH REV:0



Slave - VIT71053.55 LOGAH REV:0



Thanks Dan
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Old 07-18-2012, 07:50 AM   #8
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Default Re: Faulty 42LG3000 Help!



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Old 07-18-2012, 07:58 AM   #9
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Default Re: Faulty 42LG3000 Help!

Okay on these sets the two inverters work with each other.

If the master is dead you will usually get nothing at all on the screen.

If the slave is dead you will sometimes get a brief flash or 2 seconds to black.

Each of the boards has a fuse on it; the white chunky object next to the power connector. Check this fuse with your meter.
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Old 07-18-2012, 08:01 AM   #10
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Default Re: Faulty 42LG3000 Help!

The fuse is fine. Dan
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Old 07-18-2012, 08:06 AM   #11
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Default Re: Faulty 42LG3000 Help!

Quote:
Originally Posted by danjcarr1 View Post
The fuse is fine. Dan
On both? Okay, it looks as if all the controller stuff happens on the master. The slave is a "dumb" board.

There are some transformers on the boards; check the resistance between the markings (attached) on both boards.

If the transformers are good, the resistances will match within 3%.
Attached Images
File Type: jpg inverter.jpg (101.5 KB, 86 views)
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Old 07-18-2012, 08:14 AM   #12
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Default Re: Faulty 42LG3000 Help!

Yes fuses are fine on both. What setting do I need the meter on to check the reistance? Also do i need to put one end on the first red marking and the other end on the other red marking?
Then the same for the green markings?

Dan
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Old 07-18-2012, 08:30 AM   #13
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Default Re: Faulty 42LG3000 Help!

I have set the multi meter to 20k ohm and unless i am doing something wrong i am not getting any readings from any of them?
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Old 07-18-2012, 08:57 AM   #14
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Default Re: Faulty 42LG3000 Help!

Quote:
Originally Posted by danjcarr1 View Post
I have set the multi meter to 20k ohm and unless i am doing something wrong i am not getting any readings from any of them?
One probe on one red, one probe on another red. Repeat for green. If you are still not getting a reading they might be wired differently to how I expect.
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Old 07-18-2012, 11:16 AM   #15
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Default Re: Faulty 42LG3000 Help!

Yeah that is what I tried. Not getting any readings.
Also tried on both inverters.

Dan
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Old 07-18-2012, 11:45 AM   #16
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Default Re: Faulty 42LG3000 Help!

Can you post a side-on picture of the transformers?
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Old 07-18-2012, 11:49 AM   #17
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Default Re: Faulty 42LG3000 Help!

Yes, will do it tomorrow as the tv is at my parents home. Thanks Dan
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Old 07-19-2012, 07:47 AM   #18
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Default Re: Faulty 42LG3000 Help!



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Old 07-19-2012, 07:56 AM   #19
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Default Re: Faulty 42LG3000 Help!

Okay so as far as I can see they are wired as I would expect. What range were you using your meter on?
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Old 07-19-2012, 07:59 AM   #20
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Default Re: Faulty 42LG3000 Help!

I tired it on 2k and 20k. I have tried taking a reading from an inverter that i know works from another tv and i am getting a reading from that. Just not from either of the two inverter boards for this tv. Dan
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