Power Supply Board Voltage Readings

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Samsung Television

Repair guides and support for your Samsung TV.

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Garry Pop @gpospish

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게시일: 2021년 1월 11일

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Power Supply Board Voltage Readings

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?

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Hello, I hope you are doing Well.

The backlight of my tv is not working.

On the CNL802 I got those readings:

PIN 1+: 225V

PIN 1-: 0V

PIN 2+: 0V

PIN 2-: 0V

(Same readings whatever if I plug/unplug the backlight from the power board).

I should have also voltage in the PIN 2+ no?

Or is it the normal behavior of a power board

Great thanks

Ted Karter 의 2022년 7월 6일

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jayeff @jayeff

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게시일: 2021년 1월 12일

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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.

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I reconnected LED cable and disconneted cable going to mainboard. Readings going to main board at the CNM803 plug are 12.7 v, 12.7 v, 12.7 v, 12.7 v and 0.

I will have to wait until I receive and install my new LED strips to see if TV works.

I do appreciate the info why I am getting such high readings because the power supply board is trying to supply voltage to turn on all the LEDs even with no LEDs in circuit.

Garry Pop 의 2021년 1월 12일

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Hello, I hope you are doing Well.

The backlight of my tv is not working.

On the CNL802 I got those readings:

PIN 1+: 225V

PIN 1-: 0V

PIN 2+: 0V

PIN 2-: 0V

(Same readings whatever if I plug/unplug the backlight from the power board).

I should have also voltage in the PIN 2+ no?

Or is it the normal behavior of a power board

Great thanks — Ted Karter
I reconnected LED cable and disconneted cable going to mainboard. Readings going to main board at the CNM803 plug are 12.7 v, 12.7 v, 12.7 v, 12.7 v and 0.

I will have to wait until I receive and install my new LED strips to see if TV works.

I do appreciate the info why I am getting such high readings because the power supply board is trying to supply voltage to turn on all the LEDs even with no LEDs in circuit. — Garry Pop

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Power Supply Board Voltage Readings

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