This model does have a high rate of LED backlight failures that can damage the power supply. The diode in the circuit is a usual suspect in this case.
I replaced a board previously but got this model in again and had previously ordered replacement LED controller ICs since I suspected it may have been damaged.
With a TV to test my old board and replacement parts in hand. I compared the two BN44-00789C power supply boards. With no load, D- (negative connection) to LED strips is 0V on the good board and unstable 0 to 16V on the bad board. On the D+ side, both boards were 178-180V stable. I replaced D9801C (SB26G) since I suspected it may test good and still be failing with no change and replaced IC9805 (7014X) with no change as well.
The main switching FET and power sense resistors also test good.
Circuit is supposed same as MAP3511 base on this thread. https://www.badcaps.net/forum/showthread.php?t=82041
I replaced a board previously but got this model in again and had previously ordered replacement LED controller ICs since I suspected it may have been damaged.
With a TV to test my old board and replacement parts in hand. I compared the two BN44-00789C power supply boards. With no load, D- (negative connection) to LED strips is 0V on the good board and unstable 0 to 16V on the bad board. On the D+ side, both boards were 178-180V stable. I replaced D9801C (SB26G) since I suspected it may test good and still be failing with no change and replaced IC9805 (7014X) with no change as well.
The main switching FET and power sense resistors also test good.
Circuit is supposed same as MAP3511 base on this thread. https://www.badcaps.net/forum/showthread.php?t=82041
Attached Files