Vizio e550i-b2 power but no sound or picture, tried seeing…

Okay, the t-con board is suspected which gets video data from the mainboard and sends to the internal circuitry of the display panel/ the screen

I hope you got an identical replacement mainboard that has the same part number as of the old mainboard of the TV

this is the t-con board for that model > https://www.shopjimmy.com/auo-55-55t10-c04-t-con-board.htm

and for the backlight issue, the LED Driver board OR the backlight LED stripes to need to be checked

https://www.shopjimmy.com/vizio-91-76q02-001g-led-driver.htm

https://www.shopjimmy.com/vizio-led-strips-for-e550i-b2-tvs-with-serial-beginning-lwj2ppaq-12-strips.htm

https://www.shopjimmy.com/vizio-56-38005-030-led-strips-12-strips.htm

Let me explain, backlight and t-con board functions are different

With no backlight, you should get dim image with the help of a good flashlight

If the backlight is working, meaning the screen glows but no image then the t-con board is suspected/ not working

Your TV has both issues at the same time

As per the original symptoms, mostly the mainboard found defective and make sure you got an identical replacement mainboard that has the same part number as of the old mainboard found in the TV

Regarding no sound issue, there should be a video source/ device connected to the TV for the sound and picture

Usually, Samsung Tv does sound a melody when turning on the power

Okay, was that Tv hit by lightning that can damage all of the boards on the TV?

Thats correct, first the screen must be glow then an image/ picture should appear

Sound output is the last thing worry about

I would recommend returning the mainboard to the supplier and ask for another replacement mainboard as the existing board seems faulty and causing the issues

Thanks

Because the Tv didn't get a lightning strike and there is no other obvious reason for the current symptoms of the TV after mainboard replacement that controls all of the functions of the TV

One more thing, make sure all the cord/ connectors are plugged securely and tight on the mainboard, power supply board, t-con board, LED Driver board

Yes, a faulty t-con board won't shut off the backlight and sound output

A faulty LED driver board won't shut off the sound output but the screen goes black and you still can observe a dim image with the help of a good flashlight test

However, a faulty mainboard can cause all of those symptoms

Old mainboard wasn't booting up so no power light, this replacement mainboard changes only the power on-off function, rest is still not working

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If I cannot see an image what board controls that? > T-Con board

T-con board gets video data from the mainboard, further process it and provides to the internal circuitry of the display panel/ the screen

Thanks

Let me summarize it

Please make sure all the cord/ connectors are plugged securely and tight on the mainboard, power supply board, t-con board, LED Driver board

If all looks good, I would recommend returning the mainboard to the supplier and ask for another replacement mainboard as the existing board seems faulty and causing the issues

Thanks