Backlights work but no sound. Replaced TCON board. No sound or picture, backlights still working. Replaced main board, sound works but no picture, backlights still working. I'm now stumped. help!!

Just change everything, or take this advice.

https://www.fixya.com/support/r29790007-repairing_own_television

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Hi Pat, I'd test F1 on the tcon board to see if it's blown, if it tests ok try a main board, only way to know for sure if the main is outputting video to the tcon would be with a scope

It won't be the tcon board, could be either the main or backlights, check the backlight on terminal at the power board, should see about 3 volts there

Start by unhooking the cable from the main to power board, see if you get backlights. That will tell if the backlight section is working

Shopjimmy tests their boards but a main can be damaged if it's not handled properly, it's very sensitive to static damage. Remove the flat strips going from the tcon to the panel boards, clean them and look closely to be sure there isn't any bent or broken contacts, do the same with the LVDS cable going from main to tcon. Next thing to do is check the fuse on the tcon board, if it's blown don't order a new board but throw the set out as the panel is defective. If the fuse is ok I'd send the main back and get another one from shopjimmy as it sounds like this board is bad.

Hi Tim,
If all the boards you replaced were good and working, the only thing remains is the panel if the backlights are on. Please see that the LVDS cable is carrying voltage to the Tcon board.
Good luck.

If you can hear the audio, there should be video too; because, without video, the audio will be muted. I assume something wrong with the LVDS cable. Check it. If you wish to get some details; check the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/

The symptoms you described would indicate the backlights are not working.

The 2 main reasons are the backlight inverter board has gone or the backlights have blown!

Since you have replaced the inverter board with a new working one then this would point towards the LED backlights.

Main board. T con board is only involved with video issues. Main board goes both ways and since you already replaced the T con board that is your only alternative. U got backlite so inverter board is good.