Haier 50E3500A - No Backlight

[Tech_Jedi]

Hi,

I'm fairly new to electronics repair (I started with mobile devices) so please forgive me if I am not as clear as I should be.

This LCD tv has image but no backlight. The backlights flash on for a spiit second when powering on the tv and go out. I spent a lot of time looking for a schematic or servicing manual for this TV but I was unable to find one. If anyone can point me in the right direction in that regard that would be amazing.

I have checked all the output voltages from the PS board and all of the ones that are listed on the board are good. The PS board does not say the output voltage for the backlights. It simply says LED+. Both outputs to the LEDs showed roughly 95V. That seemed like it was likely a good measurement so I went ahead and removed the LCD panel and backlight layers and checked out the backlights.

This Model has 12 LED strips with 6 LEDs per strip. I tested and found that one of the LEDs was out and I assumed I found the problem. I ordered a replacement LED strip and installed it yet I am still getting the same result.

My bench power supply doesn't go above 30V so I am unable to test the whole backlight circuit with direct power to get an idea if it is due to the PS output.

Any help would be greatly appreciated.

Thanks!

[neilc6]

Re: Haier 50E3500A - No Backlight

You probably have more bad LEDs. Did you test every strip since they are likely 3V x 6 = 18V

[Tech_Jedi]

Re: Haier 50E3500A - No Backlight

I thought I checked them all but I suppose I could have had a brain fart and skipped one strip. I really don't want to remove that 50" LCD again but I suppose I should probably just do it and check them again. Every time I have to remove a bigger one my heart rate doubles haha.

[Tech_Jedi]

Re: Haier 50E3500A - No Backlight

Is 3v standard per LED?

If so shouldn't I be seeing an output closer to 110V then and maybe my output voltage is low?

[Tech_Jedi]

Re: Haier 50E3500A - No Backlight

Here are some pics.

[neilc6]

Re: Haier 50E3500A - No Backlight

3V (actual 2.7V) is standard but there are some that use 6V with a super thick lens. 2.7V x 36 = 97V

You can also turn on the tv with the panel disconnected and watch the backlights flash or come on to figure out if they are lighting up.