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My Samsung TV UN50H5203AF suddenly went black . I had sound and the power on off lights worked but no picture. I removed the back panels and tested the led lights. Only 8 of the 60 lights were still good. If I replace the led lights with new strips will that solve my problem? I did some readings on the power supply board at CNL 802 where the led connector plugs into. With the led connector unplugged In Standby mode pin 1 read 260 volts all the other pins read 0. Power on mode pin 1 read 382 volts and all the other pins read 0. I took readings at the CNM803 plug in standby mode. UN pin -2.3 v, PWM_BLU-3.3v, PS.ON -4.4v, GND-0v, GND-0v. There is a stamp on the board that has STB:8V ON 13V in a box pointing to JP817 wire. My readings on this wire were STB:11.4V and ON 12.7V. Do these readings show a good or bad power supply board?
Hi @gpospish , Disconnect the power from the TV and then plug in the LED backlight power cable and unplug the mainboard/power board cable. Reconnect the power to the TV and then check the voltage readings on the power board. Your initial high voltage readings on the LED power connector are basically correct as the power board is trying to drive up the voltage to the LEDs as high as it can (much higher than is necessary for correct operation) to get them to turn on but obviously they won’t since they were disconnected. When the mainboard is disconnected from the power board and power is applied to the TV, the power board is turned on full power, so you will be able to verify the voltage readings that go to the mainboard except for the standby power reading. Once you have fixed the LED problem, (they need to be fixed anyway) then check again. The red standby light on the TV should come on if the mainboard receives the correct voltage from the power board and you can test it then.
