Hello TV experts! I have a UN55D6900. The successfully TV turns on, and the backlights light up, and I get a picture, but there is a section that is dim. I took it apart and 1 out of 4 segments of backlight LEDs are not lighting on both sides of the TV (in other words, the same segment is out on both LED strips).
I tested the LED strips with my LED tester and all of the LEDs light properly, so I believe the problem is with the PSU/LED driver board (BN44-00428B). The voltages at CNM810 (between PSU and main board) look ok to me. The voltages at CNL801A and CNL801B look off for one of the 4 LED driver circuits. I've bolded the voltages below that seem wrong to me.
CNM810
PWM_DIM4 0.265v
PWM_DIM3 0.265v
PWM_DIM2 0.265v
PWM_DIM1 0.265v
B13V 12.75v
BLU-ON 4.71v
GND 0
GND 0
ASV 5.40v
PS-ON 3.3v
NC 0
---------------------
OD_Level 3.253v
OD_ON 3.278v
GND 0
B13V 12.75v
B13V 12.75v
Vamp 1.789v
Vamp 1.789v
GND 0
B5V 5.39v
B5V 5.39v
NC 0
CNL801A
L2+ 99.7v
L6+ 101.3v
L1- 40.8v
L5- 42.1v
L8+ 100.8v
L4+ 68.0v ???
L7- 41.6v
L3- 14.69v ???
IF1 2.97v
IF2 2.97v
CNL801B
R7+ 161.8v
R3+ 126.8v
R8- 100.8v
R4- 68.0v
R1+ 160.8v
R5+ 162.3v
R2- 99.8v
R6- 101.3v
I also checked the voltages on either side of each diode in the 4 LED driver circuits (top voltage, bottom voltage)
D9451 161.6v / 126.8v
D9351 162.0v / 126.8v
D9251 126.8v / 126.8v (I think this driver circuit is bad)
D9151 160.5v / 126.8v
I've included images of both the front and the back of the LED driver circuits on the board. Looking for help on what I should test next to pinpoint what part of the driver circuit is bad and which component(s) need to be replaced?
THANKS!!
P.S. I did find this thread, but it focused on relay clicking/lack of power on, not faulty driver circuits. There are some schematics in there though.
I tested the LED strips with my LED tester and all of the LEDs light properly, so I believe the problem is with the PSU/LED driver board (BN44-00428B). The voltages at CNM810 (between PSU and main board) look ok to me. The voltages at CNL801A and CNL801B look off for one of the 4 LED driver circuits. I've bolded the voltages below that seem wrong to me.
CNM810
PWM_DIM4 0.265v
PWM_DIM3 0.265v
PWM_DIM2 0.265v
PWM_DIM1 0.265v
B13V 12.75v
BLU-ON 4.71v
GND 0
GND 0
ASV 5.40v
PS-ON 3.3v
NC 0
---------------------
OD_Level 3.253v
OD_ON 3.278v
GND 0
B13V 12.75v
B13V 12.75v
Vamp 1.789v
Vamp 1.789v
GND 0
B5V 5.39v
B5V 5.39v
NC 0
CNL801A
L2+ 99.7v
L6+ 101.3v
L1- 40.8v
L5- 42.1v
L8+ 100.8v
L4+ 68.0v ???
L7- 41.6v
L3- 14.69v ???
IF1 2.97v
IF2 2.97v
CNL801B
R7+ 161.8v
R3+ 126.8v
R8- 100.8v
R4- 68.0v
R1+ 160.8v
R5+ 162.3v
R2- 99.8v
R6- 101.3v
I also checked the voltages on either side of each diode in the 4 LED driver circuits (top voltage, bottom voltage)
D9451 161.6v / 126.8v
D9351 162.0v / 126.8v
D9251 126.8v / 126.8v (I think this driver circuit is bad)
D9151 160.5v / 126.8v
I've included images of both the front and the back of the LED driver circuits on the board. Looking for help on what I should test next to pinpoint what part of the driver circuit is bad and which component(s) need to be replaced?
THANKS!!
P.S. I did find this thread, but it focused on relay clicking/lack of power on, not faulty driver circuits. There are some schematics in there though.
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