LG 22LK330 - no backlight

[bigswagi12]

Greetings from Portugal,

After spending some time online and making 0 progress i must ask for your help.
I picked up a LG 22LK330 and some other things from a e-waste bin. I fixed everything else but cant seem to fix this TV.

Problem:
AC plugged IN --> TV displays red light (standby LED)
Pressing power button --> TV light LED flashes red but doesn't turn blue.
TV no image no back light no nothing, only red light like before.
I open TV and find bug inside, killed bug.
After visual inspection boards look good no burns no nothing
--------------------------
With everything disconnected from power board and AC IN
Top right connector:

NC-
AD|M-
BD|M-0.03V
EN-
OLP-
GND-
3.5V-3.45V
3.5V-3.46V
GND-
GND-
15V-15.08V
15V-15.04V

Left top connector going from top to bottom 0V on all.

With everything connected and AC IN and click power button
Top right connector 15v and 3.5v is the same but BD|M goes to 0.11.

Still 0V on all left connectors.

No backlight no flashes no nothing. 0!
Only stupid standby light flash red slowly.

Any thoughts?

Thank you for your time.

PS: pics not from me, my camera suck.

[budm]

Re: LG 22LK330 - no backlight

Service manuals: https://elektrotanya.com/showresult?...oria=&kat2=all
It looks like the main board is not sending the EN (BL-ON/INV-ON), or the Dim control signals.

[bigswagi12]

Re: LG 22LK330 - no backlight

Hello! Thank you for your taking time to help me!

After studying the INV_CTL signal i discovered its made in the IC1002 (uPD78F0514)(NEC_MICOM). Ok so i followed the signal around and it comes out of the IC1002 at 3.8V and it go to R7515, comes out at 0.6V and gos into base of transistor Q7502. After that i get 0 volts on collector and emitor. After transistor it go to the big connector for power pcb. So after googling around i found someone who jumped the transistor with a wire and got backlight. So i did the same thing and it worked! So the problem now is this transistor why is it not working like normal? Does it need to be replaced or the problem is elsewere?

Thanks again
Uploaded manual on google drive

[budm]

Re: LG 22LK330 - no backlight

Hello! Thank you for your taking time to help me!

After studying the INV_CTL signal i discovered its made in the IC1002 (uPD78F0514)(NEC_MICOM). Ok so i followed the signal around and it comes out of the IC1002 at 3.8V and it go to R7515, comes out at 0.6V and gos into base of transistor Q7502. After that i get 0 volts on collector and emitor. After transistor it go to the big connector for power pcb. So after googling around i found someone who jumped the transistor with a wire and got backlight. So i did the same thing and it worked! So the problem now is this transistor why is it not working like normal? Does it need to be replaced or the problem is elsewere?

Thanks again
Uploaded manual on google drive

That drive signal to the Base of the transistor needs to go 0V to turn off the transistor to allow the E-C Voltage to go high which will then turn on the Backlights circuit. So if you short out the Base to Emiiter, that will turn off the transistor which in turn will turn on the backlights circuit. Now since you are able to get the backlights to come on, then if everything else on the main board, T-CON board, and the LCD panel are OK then you should see the pictures on the screen, if not the you have more than just bad backlights on signal problem.
Bad EEPROM?

[bigswagi12]

Re: LG 22LK330 - no backlight

That drive signal to the Base of the transistor needs to go 0V to turn off the transistor to allow the E-C Voltage to go high which will then turn on the Backlights circuit. So if you short out the Base to Emiiter, that will turn off the transistor which in turn will turn on the backlights circuit. Now since you are able to get the backlights to come on, then if everything else on the main board, T-CON board, and the LCD panel are OK then you should see the pictures on the screen, if not the you have more than just bad backlights on signal problem.
Bad EEPROM?

Yeah after trying to get into position to see screen and short the transistor at the same time i discovered backlight only flashes and standby led does not turn blue, so must have serious signal issues.

[bigswagi12]

Re: LG 22LK330 - no backlight

Im going to try to check all signals made and recevied by the IC1002 to see if there is problem. Another thing this IC1002 is microcontroler like arduino uno rectangular chip? So it can be reflashed? I was thinking if IC1001 EEPROM must have backup code incase IC1002 goes bad? There must be a way to reset it to the way it was. Anyway going to check signals of IC1002.
Let me know what you think of this.
Thanks

[bigswagi12]

Re: LG 22LK330 - no backlight

Im going to try to check all signals made and recevied by the IC1002 to see if there is problem. Another thing this IC1002 is microcontroler like arduino uno rectangular chip? So it can be reflashed? I was thinking if IC1001 EEPROM must have backup code incase IC1002 goes bad? There must be a way to reset it to the way it was. Anyway going to check signals of IC1002.
Let me know what you think of this.
Thanks

Ok so i check micom receiving signals and it looks good, it has st voltage, when i press button to turn on tv it receives it good so on normal input signals for startup it should be good. But on sending signals it not so good, it always sending high signals for things it should not like lcd panel control cannot turn on cuz voltage is too high for transistor same with lcd inv on. So i assume this micom is problem. What are my options? Try to connect via serial ttl and get a console to see if it says error, dump the eeprom, heat chip with hairdryer, maybe it has reset to factory button? or just hotwire all circuits to always on and put tv with switch on AC cord.