M701d-A3 Picture with no backlight

[Plurxtc1]

This TV has no backlight but has picture. I checked the edge-lit LEDs and all of the LEDs light up with the tester. Does anyone have this service manual? The output from the power supply to the LED driver does not label the voltages. Also the capacitors by the connector from the power supply to the LED has no output compared to the capacitors near the power supply to the main board which has a 12V output. Do you think I am having an issue with the power supply or the main board?

[R_J]

Re: M701d-A3 Picture with no backlight

I checked the edge-lit LEDs and all of the LEDs light up with the tester

did you have the lcd removed so you could see that EACH led was lit? or did you just observe the backlight was lit with the lcd still in place?
What voltage do you have on the LED-ON pin?
Monitor the voltage across C313 when the tv is first turned on to see if you get any voltage before it goes into protection.
Also check the voltage across one of the primary caps (M11~M12) in standby it should be 160vdc, when the tv is turned ON it should be around 385vdc, careful this is HOT primary side of the power supply

[DXseekerMO]

Re: M701d-A3 Picture with no backlight

If you are using a backlight tester the output in mA is likely less than the mA supplied by the Power Supply. I've had backlights light up just fine with a tester but not light up with the Power Supply due to bad LEDs.

If you can get to and see the menu by shining a flashlight on the screen try turning the backlights down and see if they pop on. If so there's likely one or more LEDs that are breaking down under higher current.

[Plurxtc1]

Re: M701d-A3 Picture with no backlight

I replaced the power supply, the capacitors to the backlight shows up 80V. I plugged in the backlight and the lights came on.