⟐ Commented April 13, 2026 at 5:58 MST

Voltages Primary Cap - 230v

3v3_stb - 3.3v

TP_12VB+- 12.3v

TP_12VA+ - 12.3v

1V8_M - 1.8v

VDDC_CPU - 1.07v

3V3_M - 3.3v

3V3_TUN - 3.3v

VDDC - 1v

VCC_Panel - 0v

5V_M - 5v

5V_STB - 5v

Not sure if the VDDC at 1v is correct I guess not. Can't find the PWR_On test point to check

I am thinking maybe a corrupted Firmware / Software what other tests can I try?

Also this is a Mainboard and Power Board is a all in one board

I think I can test and replace boards myself (with some guidance) if I know which one is faulty.

Thank you all in advance.

Update 6/8/2024

After a bit of hunting I found the service manual for my model TV.

Here is the link: https://research.encompass.com/SON/rr/XR...

I followed this troubleshooting diagram for the 4x blinking code, but I am getting different results with voltage readings when the TV is booting up, or TV on but blinking 4 times, or off in standby mode.

In other words I get the 3.3V or the 0V at both testing points at different power states of the TV.

So my question is, when am I supposed to be reading these voltages?

While it is booting up, after is has booted and is blinking the code, or plugged in but off in standby mode?

⟐ Answered April 12, 2026 at 22:55 MST

When it happens, there is no picture or sound, the same as if I had manually turned off the TV via the remote, but with one exception: the VIZIO logo on the bezel beneath the screen remains lit, and is 'brighter' than it is normally when the TV is on. Other than the brightly lit logo, the TV appears to be in its normal off/standby state. In fact, if I then press the power button on the remote, the TV turns back on and all is well again (picture and sound) until the next time it decides to randomly turn itself off again.

After doing some hunting around online, I found many other VIZIO customers complaining of similar symptoms, although in most of those cases I the TV either failed completely (wouldn't turn back on), or the user had to unplug the TV, wait 10 or 15 secs, then plug it back in to get the TV working again (I've never had to do that). And no one described their TV's logo as still being lit when the TV failed.

Since most of the failed cases I read about turned out to be a bad power supply board, I went ahead and purchased one online. It was an exact match to mine, right down to the board's manufacturer, part number and rev letter. I went ahead and swapped the boards, powered the TV back on, and within a couple of minutes it failed again with exactly the same symptoms. %#*@.

So at this point I can safely assume that either the problem is *not* the power supply board, or the replacement power supply board I bought online has exactly the same problem as mine (certainly a possibility; I'm sure the board I purchased was used).

I have a hunch that the TV's hardware is ok, that this is some sort of glitch in the firmware. I can imagine there are points in the code where the default action in response to some error condition is to put the TV into the exact same state I'm seeing now. I could test out that theory by reverting back to an earlier firmware level and see if the problem disappears or the symptoms change, but it appears VIZIO offers no way to do that -- not only is there nothing in the TV's menus for loading firmware, but there are no firmware downloads offered on VIZIO's own support site.

I have no service manual or schematics for the TV, so I'm pretty much stuck at the moment.

The problem of course is that I have no way to capture the TV's state at the instant it fails. So checking voltage levels after unplugging the TV and plugging it back in will likely be futile, unless a component is 'on the edge' or out of spec. I could try operating the TV with its back off and, after it fails, leave it plugged in and measure voltages then, but that would be hard to do as the TV is still in daily use.

Because the TV is still in use, any 'try this, try that' type troubleshooting will be painful, as it would mean pulling the TV off the wall, removing the 10,000 screws from the back, testing whatever new steps are suggested, then, short of coming up with an actual fix, reassembling it and remounting it on the wall. So I'm hoping I can get a bit closer to the source of this problem without having to continually open up the TV.

Just an update to my original post:

I was able to locate online a replacement power supply board for my Vizio 42" LED TV (model E422AR). I pulled the back off the TV, removed the old PS board and installed the new one. Everything worked as well as it did before, but the random shutting off problem still occurred. The company I purchased the PS board from were great to work with. They offered me a full refund, or would send me a second board to try, just in case there was something wrong with the one they sent me. I picked option 2 A week later I repeated the process of swapping out my TV's PS board for the new one. Sadly, the problem still occurs.

Here's the thing. I haven't see this problem show up now for almost two months, even though the TV is typically on several hours each day. I don't believe the problem is heat related; there's been plenty of days when the temperature of the room the TV is in topped 80 degrees F. (the vent ports are clean and there's plenty of air flow behind the TV.) I thought this problem might be related to variations in the power line voltage, but my TV is plugged into a UPS (battery), so I doubt that's the cause. I still think this is some sort of firmware bug, but without a way to track firmware updates, there's no way for me to be sure.

Another update to my original post...

It's now been four months since I’ve seen a single reoccurrence of my Vizio TV randomly turning itself off.

Given how frequently this was happening to me before - sometimes several times an hour - it is hard to believe this is simply good luck. I continue to use the TV daily, no less frequently than before.

I’m happy to have the problem gone, but have the uneasy feeling it will be back again eventually.

My only explanation for the problem’s disappearance is that Vizio downloaded and installed a new firmware update on my TV that corrected the problem (I’ve always suspected this problem was either a bug in the firmware or could be corrected in the firmware). I hadn’t been keeping a close watch on my TV’s firmware version number, so it might have changed without me knowing it. Too bad Vizio doesn’t inform you when it installs a new firmware update, or makes visible on the Info screen when the last firmware update was installed. Not such a smart TV after all.

Has anyone else had this or a similar problem simply disappear after a while?

⟐ Commented April 12, 2026 at 21:52 MST

⟐ Commented April 12, 2026 at 2:31 MST

⟐ Answered April 11, 2026 at 19:35 MST

Whenever I push the volume up and down buttons on the remote the television turns off or on after a delay. There is no way to get the volume to turn up. There is no sound.

Do you have any idea how I can fix this or what I need to replace? The television screen works fine.

And just for information purposes - the remote works fine it seems to change the channels so I'm not sure if it is a remote problem or a television problem.

⟐ Answered April 11, 2026 at 18:51 MST

A few days ago I started experiencing Samsung UN75NU800DF rebooting issue and I am hoping someone can help.

This 75" UN75NU800DF is 5 years old and started to reboot itself, like turning on then off with a relay click sound. After some google and youtube I tried some troubleshooting.

I removed the back panel and checked the power board for any irregularity, and the capacitors and solder joins look fine. I then disconnected the ribbon cable between the power and main boards and powered on the tv. Clicking stop and backlight stayed on.

I then tested each pin out for the ribbon cable with a digital meter and the output voltages match to the pinout diagram on the power board (13v but tested to be around 12.8V). At this point I am thinking the power board is working OK.

Next I tried removing each of the two ribbon cables between the main and the LCD boards (labeled 1 & 2 in the photo below) in turn to test if it's LCD problem. First the top cable is removed (the bottom is still connected to the main board) and powered on the TV. The TV turned on, sound is on, remote is working, backlight is on, but no picture. Then I did the same for the bottom ribbon cable while leaving the top cable connected, same thing happened. Finally I disconnected both the ribbon cables and again, sound, backlight, remote are all working but no picture.

Finally, I reconnected everything back to original and sure enough, the TV went back to rebooting and clicking.

My question is what can be the issue? The power board seems to be working, backlight stays on if not connecting to the main board. Can main board be the problem? Or is LCD driver board the issue and I nees to try the tape off method?

Thank you very much.

The connection where the ribbon cables terminate is shown below:

It's showing the area of the incoming power cable connector and first ribbon cable to the LCD board

⟐ Commented April 11, 2026 at 18:27 MST

Here's photos of the boards in the tv.

⟐ Commented April 11, 2026 at 18:14 MST

⟐ Commented April 11, 2026 at 17:59 MST

The TV was working just fine in the morning. Went out and came home to the red light flashing and a little click but nothing. I've already tried unplugging then holding the power button for 30 seconds, taking batteries out of the remote and even leaving it unplugged overnight. Any ideas on what it could be would be greatly appreciated!!!

⟐ Commented April 11, 2026 at 13:51 MST

⟐ Commented April 10, 2026 at 23:10 MST

⟐ Commented April 10, 2026 at 21:42 MST

⟐ Commented April 10, 2026 at 21:39 MST

⟐ Commented April 08, 2026 at 20:01 MST

When you switched it on , it go off and on

Translation Hindi → English

The TV display won't turn on.

The TV won't turn on even after turning on the power.

⟐ Edited April 08, 2026 at 6:06 MST

⟐ Answer edited April 08, 2026 at 1:45 MST