Vizio M50-C1 UHD 4k Audio only no Video Black screen Which board to replace?

this is not vizio tech support try a local repair shop

Are you saying that the same picture is split into two, or that there are 2 images split on the screen? Might be the PIP board or setting on the remote that is bad.

You might want to check the VIZIO website for help. Given how cheap even 4K UHD TV's are today, probably not worth fixing again. Unless under warranty, of course.

Chances are your T-con may be bad . I would check the backlight by shining a flashlight by the screen to look for an image on the screen . If an image is present, then the backlight is the problem. Your Tcon and main board could be ruled out, if this is the case . At this point check the power board for voltage to the led driver. The leds could have issues.

The T-con board is inexpensive. Try replacing it. You will find one online for cheap price with a google search.

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main digital board.

1. Screen buffer test: Disconnect the two flex cable between the T-CON board & the screen one by one to see if one cable is disconnect the picture is come on a half a screen or not, if it does, the screen buffer board is bad that is not fixable, you need a new screen.
2. If the buffer test with no result, i will try a new main board.

If you have no picture and no sound, go with the main board first since that board works with both. If you have sound try the t con board first since it specializes in the video that appears on our screen..

Check power supply capacitors.

Most likely you have a backlight problem. To verify this, dim the lights in the room. Take a bright flashlight, turn on the set, and shine it on the screen. If you see a faint picture, you have a backlight fault. Your backlight inverter may be built into your power supply board. If this is the case, you will have to replace the inverter/power supply board