No backlight but has power, did some tests

I have a LG 55lw5600 that's has no picture. It also has no backlights when powered on. I found a service manual online and started checking voltages. From the tests I have done so far I can tell the smps is good and the inverter is good (by tests that use jumper wires), the led lights come on during this test when ac power is applied. I have done the flashlight test and see nothing. Any ideas on which board or components may need to be replaced or what I should check to narrow it down farther.

Thanks for your time,

Neal Pollman

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Thank you for your response, I will get all my voltages for you and post them for you to view

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I basically have the same problem. Does the power standby led stay blinking red or does it go to white (blue)?

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3 Answers

@ntpollm if every part you have tested is truly okay then there is an issue with the backlight not getting signal. Connector P202 and P203 go from your power supply to the LED's so the issue could be on the power board as well as the main board. Since I do not have access to the service manual right now, and since you did not tell us what connectors you have checked already, I would test checking the connector from the SMPS to the Main board (P201?) See what voltages you get on there. Also, do not forget that a bad T-con board can prevent your panel from showing anything. there should be a fuse on the T-con board. Check it out and see if you have continuity as well as 12V from the main board. Let us know what you've checked and what the values are. Post some images of your boards with your question so that we can see what you see. use this guide Adding images to an existing question

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Third pic has my voltage results. The DRV-ON voltage is very low. And the t con fuse is not getting 12 volts. The last pic the the test I did, and that is the one when the backlights came on. I am just lost on where to go next.

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I also have the training service manual if you would like me to attach it

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Had the exact same problem as the original poster (model: LG 42LW5600). I did the oven reflow trick on the controller board and it worked - 385degreeF for 10 minutes in the oven, let it cool to ambiant temp (45 min) without moving it. I'm an electronic engineer and I know how to reflow but this is (waaayyy) much faster (when it works). Cheers.

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Neal Pollmam will be eternally grateful.
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