Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

[matyka]

Hello,I would need some help with my lg 32Lc46 ,when power the unit tv comes on for about 3-4 sec all good picture and sound .
After 4sec sound stays on but no picture.
Power board is fine all reading good.
How I check the backlight invertor ? Could be the ccfl faulty ?

[Maklaud]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Hello,
Сheck resistance on all transformers.

[Maklaud]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Check

[CapLeaker]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

those transformers should be within 3% of each other.

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Hi,I checked all 8 transformers between pin 1 and 8 , pin 4 and 5 and readings are:
1.021 kohm pin1 and 8
1018 kohm pin 4 and 5
Could you let me know if I measuring the right pins ?

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

hello,I just received the photo from Maklaud and the resistance between pin 5-6 is 08.16 mohm and pin 7-8 is 08.40 mohm
Checked all 8 and they are the same value .

[Maklaud]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Sorry

[kc8adu]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

no caps in series so measure/compare at the ccfl connector.
very likely you have a bad transformer.common on those inverters.
could also be a bad lamp.

[vinceroger69]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

http://www.lcdparts.net/TransformerD...ProductID=3497

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

http://www.lcdparts.net/TransformerD...ProductID=3497

Thanks,already measured that way and I have around 1.068k on all 8 of them.
To be honest I don't think are the transformers who have failed on this inverter

[vinceroger69]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

what voltages change? on the power supply when the picture goes off.

[budm]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

The BL-ON and the Dim control signals are still present when the lights go out?

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

no caps in series so measure/compare at the ccfl connector.
very likely you have a bad transformer.common on those inverters.
could also be a bad lamp.

Thank,between the connector the measurements are nearly the same 2.043k

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Reconnected the inverter to the tv and after reading all values with the picture on and with the picture off all readings from the main board remains the same.

[budm]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

BTW, you are running the Inverter board without the shielding in place and do not see any mounting screws for the inverter board to GND the board to the chassis.
Do you have the LCD panel model number?
You may have lamps problem at this point if everything checked out fine on the inverter board.
May be you can try running video with the white back ground then you may be able to see if one of the lamps is not on, you will see horizontal gray bar where the lamp is not lit.

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

BTW, you are running the Inverter board without the shielding in place and

All the screws and the metal shield in place all the time when tv was powered on.

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Panel number is V315B1 -L07
When tv go off buzzing noise could be heard from the inverter and the screen is black no light at all.Photos attached when tv working and with the black screen sound fine.

[budm]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Well, try that white screen test in the darkened room , may be it will be on long enough for you to see if all the lamps are on.

[matyka]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

I have tested with the white screen and looks absolute fine with all the ccfl light up.
I will resolder all the transformers pins and see what happens .

[Maklaud]

Re: Lg 32LC46 Backlight cuts out after tv on for 3-4 sec

Try to block protection OZ964GN. Then try to remove one of eight transformers. And one by one test.


And by the way...

The BL-ON and the Dim control signals are still present when the lights go out?

Where's your answer?
Dim Voltage = ?
BL-ON = ?

I had a case when the backlight is blinked and inverter noise due to DIM (The problem was in the EEPROM on the main board)