Hisense 50H5G has sound no backlight

[nwcs]

I just got this one, customer was watching and the picture faded but they could still see the picture. Changed the channel and picture came back. Then later it went black. I can see the picture but no back light. I am suspecting a open led but I do not see the usual flash of back light when I turn it on. Checked the voltages to the led's 220V on red lead and 110V on white. XP805 on the power supply board is gnd, gnd, pwm is 5v, sw is 4v, 12, 12, stb is 4v, gnd then the last two are both 19v but should be 16v. Am I right in thinking it is a open led or should I be looking at something else?

[budm]

Re: Hisense 50H5G has sound no backlight

More likely open circuit in the LED strings due to open LED or open connections between LED strips.
You only has two wires to the LED strips inside the panel so the strips are connected in series to form one long LED string.

[nwcs]

Re: Hisense 50H5G has sound no backlight

Kind of what I thought. I have been replacing led strips like crazy in LG and toshiba tvs but they always seem to flash the few leds that do light up, and since they usually have more than two that makes sense. I will take the panel apart and take a look. I am not even sure if the led's are available for this TV.

[budm]

Re: Hisense 50H5G has sound no backlight

The LED strips/LEDs are connected in series like Christmas lights so one goes open circuit then the whole thing will not light up, but if the LED shorted out then the string will still light up.

[nwcs]

Re: Hisense 50H5G has sound no backlight

Removed the lcd panel and tested all of the led strips. Found two bad led's in one strip were open. I want to make sure but has anyone bypassed the led's by shorting around them?

[budm]

Re: Hisense 50H5G has sound no backlight

Not good idea to bypass, you can use 3.3V 1W Zener connected in reverse bias or use 5 1N4007 connected in series to simulate Vf of one LED.

https://www.badcaps.net/forum/showthread.php?t=46403

https://www.badcaps.net/forum/showthread.php?t=51251

[nwcs]

Re: Hisense 50H5G has sound no backlight

I will try that. I need to order the diodes first since I do not seem to have any. I just got back into TV repair after being out of it for 10 years. All of the TV repair shops in our county have closed for health or other reasons.

[nwcs]

Re: Hisense 50H5G has sound no backlight

Well it turns out I did have some 1n4728 zener's in the store soldered them in and now all of the led's work now. Thanks for all of the help BUDM.

[budm]

Re: Hisense 50H5G has sound no backlight

Thanks for the follow-up, you should also turn down the Backlights level as low as you can to extend the life of the LEDs.

[nwcs]

Re: Hisense 50H5G has sound no backlight

I do that on any tv that I replace the led's in. Thanks again for the help.