LG 42LG3000 LCD TV Fault Finding.

[cosmindaniel]

Re: LG 42LG3000 LCD TV Fault Finding.

So, yesterday i was to LG service. I have a 42LG3000 television, with this simptoms white screen but good sound. Actually i try to change T-con Module, i bought a new one, i replace all condensators, finally from service sad me this: YOUR DISPLAY IS DEAD, ACTUALLY , the matrix from this is broken, its necessary to buy a new one, but may be you need to buy a new tv.
So if you this problem, don't try to change some parts from inside, because 99% the display is broken............
Good Luck.

[cosmindaniel]

Re: LG 42LG3000 LCD TV Fault Finding.

Hye. i need a little technical support, i a have an Lg 42Lg3000-ZA and i have a white image with sound. I measure voltage from connector 1-4pins and i have a negative voltage -12Vcc, and i guess actually a need +12Vcc regulated.
do you know what voltage are on the rest of pins from 5 to 26?? I can find a scheme or diagram of this module which is T370XW02-VC/ 37T03-C00

Now i try to replace some components just like in the picture.
Thanks in advance,Cosmin.

[cosmindaniel]

Re: LG 42LG3000 LCD TV Fault Finding.

Hye. i need a little technical support, i a have an Lg 42Lg3000-ZA and i have a white image with sound. I measure voltage from connector 1-4pins and i have a negative voltage -12Vcc, and i guess actually a need +12Vcc regulated.
do you know what voltage are on the rest of pins from 5 to 26?? I can find a scheme or diagram of this module which is T370XW02-VC/ 37T03-C00

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Here is a question.

Can I swap sides with the Master and Slave to see if the Lamps OK on the left hand side?

--edit
Nope plugs are slightly different. Still looking for ways to test the components on the Slave board then.

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Nothing obvious that I can see. Looked at the white surface mounted fuse and looks in one piece. Continuity confirmed.

Here's a picture of what it looks like - should be clear enough to make out everything. Clicking it Zooms in.

https://www.dropbox.com/s/feb1j1emfo...2019.18.17.jpg

Here is a YT Video of what I get without plugging in the Slave Invertor Board -
http://www.youtube.com/watch?v=0ayUhUQm0mQ

Much much better view of the whole board - held still by glass table above it - no hand shake.
https://www.dropbox.com/s/ou2q97ka2l...2022.13.13.jpg

I'm just taking a look at the condition of the 'sync' cable at the moment... [EDIT] Looks OK.

[tom66]

Re: LG 42LG3000 LCD TV Fault Finding.

Check fuse on it, check for burnt components.

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Major update.

Unplugged the Slave and left the Master in.
Turned on the TV.

Stays on and can see 'The Fly' for a around 3 seconds.
Left hand side (Slave's side) is dark, then goes off.

Think the faulty board has been located!! Can it be diagnosed!?

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Looking back on the thread I referenced earlier, I got an idea what exactly you meant and have probed them.

This is what I get back measured using the DMM on 20k Ohms.

Master -
https://www.dropbox.com/s/dex5ce1ba91gwwk/Master.jpg

Slave -
https://www.dropbox.com/s/9xkzl4i6x32qj0z/Slave.jpg

Both are the same, so I'm hoping it's right?
Looking at them points close up like that makes them look a right mess!

[Caleb]

Re: LG 42LG3000 LCD TV Fault Finding.

Have you tested those transformers yet? You want to test primary and secondary sides with ohm meter and see if they are the same (pins marked 9 and 12 are secondary) Unless you happen to have a ring tester handy?

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

D'you reckon these need replacing or can they been repaired perhaps?

If not, can I replace them with VT71053.54 & VT71053.55 as they seem to be more widely available.

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

I'll take some fresh ones. Not sure what happened to the old ones...

Galaxy S3's have a pretty good camera!

Master Invertor Board
https://www.dropbox.com/s/rra4ivv8xx...2019.18.01.jpg
(I've tested F2 and appears OK)

Slave Invertor Board
https://www.dropbox.com/s/feb1j1emfo...2019.18.17.jpg
(I've tested F200 and appears OK)

VT71053.50 & VT71053.51

[budm]

Re: LG 42LG3000 LCD TV Fault Finding.

OK, the inverter on can be 2~5VDC, so it looks like you have all the correct voltages but there is problem in the inverter board.
I cannot see the pictures in your DROPBOX in the earlier post.
Which one of these are the inverter boards in your TV?
http://www.shopjimmy.com/catalogsear...?q=LG+42LG3000

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Aha, after turning on (and the backlight flickers and the LED goes a faint Blue)
All voltages are as they should be.

Invertor boards are receiving 24.2v.
12v is pushing out 12.3v
5v is pushing out 4.8v

Will check what INV_ON is using, but I'm expecting 24v right?

-edit
Nope. INV_ON is at 4.7v after the backlight flickers.
But on 0v before trying to turn it on (Switch at wall and before Remote Power pressed). So I'm guessing that's correct?

I'd just like to say, thank you all soooo much for your help with this. Hugely appreciated!

This looks to me like it could be the Invertor board's yeah? I've checked the surface mounted fuses and they appear fine.

[truep]

Re: LG 42LG3000 LCD TV Fault Finding.

The on/off turns the Power supply (12 and 24V) on. the inv on is the same as BL on.

[Caleb]

Re: LG 42LG3000 LCD TV Fault Finding.

If you trace the inverter on around and down it goes to the on/off pin, then right next to it is the power on which = ps on. You will want to test both and see if they are receiving a signal from the main board to turn on, as Budm said somewhere between 2-5v. If you are not receiving the signal you can force on the power supply by putting a 1k resistor between the 5v pin and the power on, same thing for the inverter on signal.

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Great guide and explained a ton!
But this is why I'm getting a little lost because PS_ON and BL_ON doesn't seem to exist on this board.

I *think* I've got it in this picture and I'm guessing it's the ON/OFF (24v?) pin I should be looking at?

Also got something called BRI there too (Somesort of Bridge?)
As well as INV_ON... which is quite obvious now I've thought about it! = BL_ON I guess?
AND Power_On also lives there too!

https://www.dropbox.com/s/6uksajpon0...2016.06.56.jpg

Confusion!

[budm]

Re: LG 42LG3000 LCD TV Fault Finding.

The 12v/24v power supply section is turn on by the Main board, the signal is typically called PS_ON. That is the pin on the power supply board you need to find out if it is receiving the turn on signal from the main board or not, PS_ON is typically about 2~5vdc. Please read my Basic LCD TV troubleshooting guide.

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Been checking pins today following this thread https://www.badcaps.net/forum/showthread.php?t=20824 - which has excellent descriptions of what to do and how! Checked the Invertor fuses, both have continuity.

Then I got to the part of '24v to the Invertor boards' and while everything is connected (and in what would be standby mode) I get nothing, nuda, zip. I've checked the 24v on the actual PSU and doesn't seem to be there either.
https://www.badcaps.net/forum/showth...937#post241937

What does this mean?
Is the TV waiting to be taken out of Standby before it feeds 24v to the Inverter Boards or should that be there already?
Or is the PSU screwed?

You are looking for a pin tagged ps on or bl on to test for the signal turning on the power supply. Try having your test probes on the 12v and get it when the back lights flash on. Usually if they come on then extinguish the inverters are at fault, but could be power supply, main or bulbs too. BTW the link is to an empty folder

Still looking for this, but I'm going to try and see if I can get 24v from the Fuse on the Invertor board to the Chassis when the LCD Panel switches on. Is it OK to do this?

[DejaVu]

Re: LG 42LG3000 LCD TV Fault Finding.

Hunted all round both boards and found this on the PSU. It's about as close as I can find.

https://www.dropbox.com/s/6vw3ehayll...2019.34.41.jpg

I'm guessing its the third pin from the left at the top marked ON/OFF. Is this the one that would be activate 12v?

I'm thinking I'll have to wrap a small wire around it, replace the connector and test it with the multimeter. This is the same connector that powers the Mainboard and looks to be the only one that does.

[Caleb]

Re: LG 42LG3000 LCD TV Fault Finding.

You are looking for a pin tagged ps on or bl on to test for the signal turning on the power supply. Try having your test probes on the 12v and get it when the back lights flash on. Usually if they come on then extinguish the inverters are at fault, but could be power supply, main or bulbs too. BTW the link is to an empty folder