Hi Jean,
my 7741 has also trouble with the backlight. Someday during televison the screen went black and never get back again. I sent the TV to my dealer for repairing but he couldn’t fix the problem. So I got the TV back unrepaired.
I read a lot of backlight problems and also watched a lot of youtubes about this topic. In your comment it sounds that you maybe fixed a problem with the backlight by yourself. Do you have any suggestions to dismantling/disassabling the TV in order to get to the LED stribes?
Meanwhile I checked most of the DC voltages of the PCBs compared to the service manual. So far I found only one DC voltage which should be 5V but it was only 3V (PCB03 P005 Pin2).
Thanks in advance Michael