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Black screen, no backlight.

I have a similar problem. Vizio 70inch LED TV. Model M70-C3. Black screen, no backlight. The power button lights up and the optical audio port lights up. I removed the back panel and checked the voltages on the Power Supply board.connector to Main Board, standby voltages for AC det =3.96, PS on =5.13 and AU =12.. Pins 8&9 VS =12v. Pins 13&14 T-con =12v, however pin 15 T-con on =0v. Also T-con connector pins 1,2,3,4 measured 0v instead 12v. Checked output voltages on LED Driver connector. Pins 3-8 measured 34v instead of 24v..Pin 13, vsense =2.6v. To summarize, zero voltage output to T-con board and higher voltage 34v instead of 24v going to LED driver board. Can you advise me on which board I should replace. My initial thought was the Power Supply board, however I guess it could be the Main Logic board not setting T-con on. Another possibility is the LED Driver board.

I need some guidance

Update (08/23/23)

OK, did all of that and measured 0 voltages on both ribbon cables at T-con board. Is it a faulty Main board ?

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@johnhamilt98534 that is a lot of really good information but it can get confusing quickly. Let's try and sort through this :-). Did you just lose the image (screen turning black) and kept the sound or did the sound stop as well. Next step would have been to shine a flashlight at an angle (with the TV on) at the screen, to determine if you can see that there is an image being produced. That would have limited the troubleshooting to the backlight.

Anyhow, for now you want to post some good pictures of all of your boards (and relative close ups of the connectors you tested). Let us know if you measured the voltages on the T-con board, not just the pins,

For now, with all your voltages etc, the power supply would be on the bottom of my list of suspects. Unless of course you found some damage specifically on the power board.

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Update (08/23/23)

@johnhamilt98534 measure the voltage on the fuse of the T-con board. Let's see if that gets power. Looks like it is label as F100. Not sure where you measured for the voltage on the ribbon cables.

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Oldturky03 appreciate your quick response. When the TV was turned on it was black screen with no sound I did the flashlight test and didn't see any images.There are no voltages going to the T-con board. Checked output connector from power board and get no voltage reading on components on T-con board. Checked all boards for signs of components damage, none. Unplugged and replugged connectors to all boards and rechecked voltages. All were correct between power supply and main board. DC voltage out to LED driver board very high, 34v instead of 24v. Not sure if this is a problem.

The T-con on = 0. to Power Board from Main board (Pin 15) This could possibly be why there is no 12v going from the Power Board to the T-Con board.

par

@johnhamilt98534 We really would need to see your boards. It is unusual for a T-con board to turn your backlights off and no sounds etc. I am not convinced it is the issue. I am leaning toward the main board or the panel

par

Ok, so you think it is the Main board. Could the LED Driver board also be suspect ?

par

@johnhamilt98534 It is a suspect :-) Disconnect the T-con board from the LCD driver boards and measure the voltages on your T-con board. First the left ribbon then the right ribbon. Disconnect the power board in between. This "When the TV was turned on it was black screen with no sound I did the flashlight test and didn't see any images" sounds like more than a bad T-con board.

par

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