I have a 55 inch vizio flat screen. it turns on but the screen fades away.

It sounds like you may have a problem with the video signal on your Vizio 55 inch flat screen TV. The fact that the TV turns on and has sound, but no video and vertical lines on the screen, suggests that there may be an issue with the video processing or display.
It could be a problem with the T-CON board, which is responsible for the video signal processing. It could also be a problem with the LCD panel itself.
It's also possible that there's an issue with the cable connecting the T-CON board to the LCD panel, or a problem with the software on the main board.
I recommend consulting the manual of the TV or contacting the manufacturer for further assistance. A professional technician should be able to diagnose and fix the problem.
It's also possible that the issue is with the mainboard or the T-CON board is not compatible with the TV. Thus, it's best to check the compatibility of the parts with the TV before installing it.

Corrupted firmware. An update is necessary. If you wish to get some details; check the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/ Firmware (Software) update procedure of many popular brand TVs and other devices are given in detail.

Return it. It is defective

Check all source is same or not
Try factory reset.

Hello Patricia,

• There is a loose soldering connection in the Main Board. That happens because the components on the are generating a lot of heat therefore melting solder connections.
• Stop beating on the TV's back, that only makes the problem worse.

• Take it to a shop.Or if you are a tech, try locating the loose connection(s) and solder it back.
• Also check your Warranty Period, It may cost you 0$. Call Vizio if you still have Warranty on the TV.
  

Here is a link to Vzio Supoport.
Good Luck,
JP
VIZIO Product Support and Services VIZIO

Hello, this may be a software glitch, contact Vizio to see if there is a software update. thanks, Terry

Unplug the set for 20 minutes then plug it back in and turn it on. You should see a setting that says HOME____STORE on the screen. Make sure you high-lite HOME. Then continue on.

Now tv is on,u have a picture only few sec.and faded away and have audio left only?Yes then the tv have 2 long board call LCD inverter boards are dead.These 2 long LCD inverter boards help the LCD screen panel to have a backlight to produced a picture.Tries websites like Shopjimmy.com,Ebay.com to buy those 2 refurbishes long LCD inverter boards for the replacement.Tv is newly bought?Return it right away for an exchange for a diffrence new one.

Well time will tell if this is a true solution but I experienced the same issue. Originally I was able to get the TV to work by turning it off and back on.

After some research I notice the the Vizio FAQ mentions a similar issue for which the solution is to unplug the unit for 3min.

After calling Vizio, they suggested that under the menu option Setup, Picture, Advanced Video Features, I should try turning off Advanced Adaptive Luma and Backlight Control.