VIZIO M50-C1, powers on, no backlight, no picture

[gustagen]

Hi All! I've had several successes repairing TVs thanks to the helpful members here. I'm back today with another TV rescued from the curb.

This is a VIZIO M50-C1. Previous owner posted it for free on craigslist with description 'powers on but no picture.' I was unable to get more information from them.

When plugged in, the mainboard LED lights solid purple for 2 seconds, then changes to solid red. As the mainboard LED changes to red, the front LED lights solid white and fades to off over 5 seconds.

When I press power on either the set or the remote, the mainboard LED lights solid purple and the front LED lights solid white. After 10 seconds it fades to dim solid white. After 7 more seconds it fades to off. At this point the set will not respond to power commands from either the set controls or remote.

There is never any backlight activity, and I cannot see any picture using a flashlight.

There is no change to the above when either or both T-Con connectors are unplugged.

I noticed what seems to be a missing screw in the upper left of the main board. Perhaps it was never installed, or perhaps this set has been serviced before. The boards seemed equally dusty and I carefully cleaned them before taking photos. Most of the tape securing the wiring was in place and the connectors are all properly installed so I don't think the previous owner was recently poking around inside.

I've looked over the boards and don't see any obvious faults. I've attached photos of the power, backlight, and main boards. I removed the metal shields covering the right and bottom sides on the main board. I can take more photos if needed.

Thanks for any help you can offer!

[neilc6]

Re: VIZIO M50-C1, powers on, no backlight, no picture

https://techhometravel.com/vizio-m43...-no-backlight/

Vizio M series have BGA failures. Lots of threads if you search M43-C1 or M65-C1. Symptom is ON/OFF (backlight on signal) pin not going high (>2.5V).

[gustagen]

Re: VIZIO M50-C1, powers on, no backlight, no picture

Thank you, neilc6. I'm slightly familiar with BGA rework because a friend had a hot air setup for repairing XBOX 360 consoles years ago.

I am currently out of town and away from my tools, so I'm waiting to borrow a DMM from a friend here.

Out of curiosity, I removed the main board and was horrified by the state of the other side. What happened here?!

I had previously noticed what I assumed was thermal compound in strange places on the main board and thought it was from sloppy assembly at the factory.

[gustagen]

Re: VIZIO M50-C1, powers on, no backlight, no picture

I've been looking at used mainboards for sale and many of them look as ugly as the one in this set.

I'm also beginning to think this is not the original mainboard. I noticed earlier that this board has several connectors that go unused in this M50-C1, like CN203, CN211, CN212, and even an extra T-Con connector. Perhaps my board is a replacement from a larger M-series model?

Replacements I'm seeing for the M50-C1 have solder pads for these connectors but they are unpopulated from the factory.

I'll reinstall this mainboard and report back when I get a DMM.

[gustagen]

Re: VIZIO M50-C1, powers on, no backlight, no picture

I got impatient waiting to borrow a DMM, so I cleaned up the mainboard and reinstalled it. I found a suitable replacement for the missing screw in the upper left corner.

I used a butane torch to heat the areas of the large black heatsink above the two processors, and the TV powered up! It's been playing YouTube for 15 minutes without issue, but we'll see how long this "repair" lasts.

Thanks again for pointing me toward the common BGA issue, neilc6!

[zape]

Re: VIZIO M50-C1, powers on, no backlight, no picture

you'll probably have to do this every few weeks or months
they say this "repair" method does not last long

[zape]

Re: VIZIO M50-C1, powers on, no backlight, no picture

I used a heat gun and a thermal sensor placed close to the heating area with some thermal paste
Heated it up to 240C, kept it at that temperature for 10 seconds and it fixed the TV
Here is the heating area

[zape]

Re: VIZIO M50-C1, powers on, no backlight, no picture

The "Fix" lasted for 1 month.
had to redo it again, this time heated up both chips to 235-240C for ~1min
will see how long it will last this time

[kris42]

Re: VIZIO M50-C1, powers on, no backlight, no picture

This is an older thread, but I had the exact same issue with an M43-C1. After trying some other suggestions I landed here and followed your advice of heating up the section of the main board behind the heat sink. And it worked! My question is, why? And why isn’t it a permanent fix? Is the heat reflowing solder, or something else? Are there particular components that need to be reseated/resoldered?

[diif]

Re: VIZIO M50-C1, powers on, no backlight, no picture

One/some of the solder balls have cracked, there is expansion of the balls due to heat and this makes a contact. It's not permanent unless you apply a suitable heat to remelt the solder balls.