lg 42lb7rf "Reverse Colors" Problem

[kobkobk]

dear friends hi,
my lg tv 42'' lcd with display problem,at last days do not turn on normally,i open and sow bad caps at the p.s and replaced them.the power on, problem has solved
then the picture was change and the the color isn't correct
don't know where to start and what's the problem?t con ,main board

[Chungalin]

Re: lg 42lb7rf "Reverse Colors" Problem

Looks like a T-CON failure. If it had the AS15-F IC, I would even say that you just need to replace that one, but as far as I can see, that U5 doesn’t look an AS15.

[saddle_au]

Re: lg 42lb7rf "Reverse Colors" Problem

Best guess, my 2c worth, is first look at the signals on the LDVS cable on the TCON side. Sometimes the cable connector needs cleaning, reseating or padding. Check the fuse and the regulator voltage. Make sure the voltage coming in on the LDVS cable is right as well (+12v on pins 48 to 51).

Also one or more of the drivers in the gamma chip on the left (the one surrounded by resisters top and bottom) might have failed and is pulling up all of the other outputs to give this color distortion. It may also be the regulator feeding the input resister chain.

The board is an LC420WU6-SLA1 and seems to be available from a variety of places. The panel file LC420WU4-SLA1.pdf does not show the schematic of the board, just the connector layouts.

I've swapped a lot of AS15 gamma chips on Samsung boards, and they can look like this when a driver has died. This is an LG/Philips panel but the gamma section works the same.

[saddle_au]

Re: lg 42lb7rf "Reverse Colors" Problem

But first,,,,,,

The panel code might be wrong in the eeprom on the main board. Early Samsungs corrupt the eeprom contents with bad power supply cap hassles. I have seen this solarisation mentioned on the web before due to wrong eeprom parameters after a mainboard swap.

https://www.youtube.com/watch?v=Q1bg9qP_qic
https://www.youtube.com/watch?v=c-aXKCTiU6I

[nomoresonys]

Re: lg 42lb7rf "Reverse Colors" Problem

But first,,,,,,

The panel code might be wrong in the eeprom on the main board. Early Samsungs corrupt the eeprom contents with bad power supply cap hassles. I have seen this solarisation mentioned on the web before due to wrong eeprom parameters after a mainboard swap.

https://www.youtube.com/watch?v=Q1bg9qP_qic
https://www.youtube.com/watch?v=c-aXKCTiU6I

I wonder if a firmware update might fix it?