Philips 49PUT4900/12 no backlight

[Repair_dane]

Hi guys,

tv turns on and works as usual, but without any backlights.
LED-tester shows that the LEDs seem to work fine (54V and 25V supply)

However the LED voltage on the board is fluctuating between 0 and 50 (can not make precise reading. Happens withing a second)

Capacitors look fine

Any ideas?

[neilc6]

Re: Philips 49PUT4900/12 no backlight

Backlight issues are almost always the backlights themselves. Your LED tester puts out a lot less current than the power supply so may not catch the failure. You will need to open up the panel and test the strips or watch them flash. They may flash if the LED hasn't failed open circuit. The reason you can't measure any voltage is because the protection circuitry is kicking in and shutting down the backlights.

[R_J]

Re: Philips 49PUT4900/12 no backlight

The power supply is likely fine, it only takes one led in the string to short to cause the backlight circuit to go into protection.

[Repair_dane]

Re: Philips 49PUT4900/12 no backlight

The voltage was measured both with and without the LEDs connected and in both cases it was fluctuating.
I will take out the LEDs later today and check the individually