Philips 65PUS6554/12 - only powers on if you prime backlights first

[djmka]

Hi everyone.
I have a problem that I would appreciate some expert advice on.
I have a 65” Philips television which powers on, has sound but but no picture. Usually this would lead me to believe an open circuit was present on the backlights. However, if I disconnect the mains power cable to the television and test the power cable going to the backlights using a LED tester, no open circuits are present. If I reconnect the backlight cable to the power board and replace the mains power cord to the tv the device fires up perfectly and displays a beautiful picture. It's almost as though the LED needs need “priming” before they will work. Has anyone come across this before?

I've attached some images showing the voltages of my LED testing (between 32v and 35v) and the voltages when the television is operating correctly (42.5v).

Any help is greatly appreciated.

[petehall347]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

yes i have had same thing .. tv lasted a few months maybe a year working ok . its waiting for me to look at it again . suspected bad contact .

[Davi.p]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Almost surely you have a single bad fluctuating led..
try this simple test, cool tv, warm up the leds power supply area (elevator), turn on tv normally, if 100% working then it's so..

[Diah]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Bad LED on 28.7V line

[Davi.p]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

what's your board model?

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Thank you to everyone that has commented. Please see attached pictures of the power board and main board.

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Davi.p - please explain what you mean by the word elevator.

[Davi.p]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

i mean the are near the leds connector, from the big inductor to the connector..

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Would it be possible to circle the area on one of the images I've submitted?

[Davi.p]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Thanks Davi.p
I’ll try this tomorrow morning and report back.

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

I tried to power on the television earlier today but it wouldn't start. I took the back off and applied heat (using my wife's hairdryer) to the area you highlighted and it then powered up successfully. Could you please explain why it works when preheating the power board. Can you also confirm that it is 100% the backlights that are faulty, Finally, has anyone had experience of unsticking the panel drivers from the chassis on a Philips tv. They are stuck in a few places making it almost impossible to free them.
Thanks

[Davi.p]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

It sounds strange to me that tv remains off with a b.light problem, what it does with standby led? does it blinks? if you change channel can you hear sound without image? The reason of the heating can be because some resistors of the feedback circuit changes slightly value and so permits the driver to turn on the lamps.. i don't know what you mean for sticky panel drivers , search youtube for a dissassembling guide..

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Update -

I finally dismantled the television to get to the LEDs and found each strip consumed varying voltages using my LED tester:-

Strip 1 - 29.1v
Strip 2 - 29.2v
Strip 3 - 33.5v
Strip 4 - 31.5v
Strip 5 - 29.2v
Strip 6 - 32.5v

Based on the above, I have decided to purchase a new set of backlights and shall let you know the outcome. Hopefully, with new lights in, the television should operate correctly.

[nomoresonys]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Quote: "Finally, has anyone had experience of unsticking the panel drivers from the chassis on a Philips tv. They are stuck in a few places making it almost impossible to free them" do you have a picture of this? not sure what you mean, the new backlights should be the fix.

[djmka]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

Hi nomoresonys. Thanks for your reply but I have already managed to separate the driver board from the chassis using the blade from a craft knife.

[nomoresonys]

Re: Philips 65PUS6554/12 - only powers on if you prime backlights first

ok, maybe it was stuck on with a thermal pad?? lol.