Power Supply and/or LED strips

[Phillydubv35]

Hello all, hope everyone is keeping as busy as possible and staying safe. I am in the midst of troubleshooting my television. It is a Sharp Roku TV, 50" model LC-50LB481U. Here's the deal...it powers up, no picture/blank screen, no backlights, but HAS sound. Performed the flashlight test. I can see the menu with the flashlight. I have it narrowed down to either the LED strips or LED strips or both. Tested the LED strips, 3 are good, 3 are bad. My first question is, would I still have some backlight being that 3 are good? I'm being told that "generally", they are all or nothing. In other words, I have the impression that they must "all" work to create some backlight, if one or more are out, they will not work at all. Is this correct? Can I get away with only replacing the bad LED strips or is recommended to replace all of them which I have been told? Secondly, I'm being told that I may also have a bad power supply board in addition to the 3 bad LED strips. I tested the LED connection where the cord plugs into the power supply board with a multimeter. However, the power supply board does not state what the operating voltage needs to be when testing. Some do, some don't, and I do not see that mine does. It is no where to be seen in the owner's manual nor can I verify it searching the web. Anyways, it did show as 63.9-64 V on average on the + terminals. Does this sound about right? I am simply trying to determine if the power supply board is good or bad before proceeding forward. Thanks in advance for the helpful replies.

[R_J]

Re: Power Supply and/or LED strips

With a bad led strip, the led power supply will detect the problem and shut down, 64 volts is just the base voltage, there will be a boost circuit that will increase it when its working properly. It is best to replace all the strips, or you will just likley be having to repair it again, and every time you remove the lcd you risk damaging it.

[neilc6]

Re: Power Supply and/or LED strips

Backlight failure is pretty common in that model and a little bit of navigation to turn down the backlight level. Even low power mode runs them at 78%. I would replace all strips with new. https://techhometravel.com/turn-down...l-in-roku-tvs/

[Phillydubv35]

Re: Power Supply and/or LED strips

Thanks for the advice guys...it sounds like you two aren't too concerned with my power supply board then?

[R_J]

Re: Power Supply and/or LED strips

These power supplies are good quality and the led drive circuit is fairly simple, maybe in few years things will be different.

[neilc6]

Re: Power Supply and/or LED strips

I've replaced strips on that model at least twice. One had a repeat failure with a repaired strip and turning down the backlight. Only see bad strips cause power supply failure in a few cases - one particular Samsung model and a few Toshibas.