Vizio E400I-B2 powering on problem

[TheCockroach]

Hello!

A friend of mine had brought me a TV to look at, to see if I could figure out what was wrong with it for him. When hitting the power button, it will flash 'Vizio" across the screen for about 1/2 a second, and then go right back off again.

I've already checked the yellow 5v wire going from the power board to the mainboard, and it's reading a solid 5v. So I'm trying to figure out how to proceed, in figuring out what the problem is. There is a very rapid "clicking" sound coming from the power supply board, but it's not very loud. Not sure if that's normal though, as I'm still not as familiar with this department as I'd like to be. And OH YEH, there was also a huge roach nest inside as well, although it seems to have been an old one, as (luckily for me) there wasn't a single live one. I'm going to assume, that the problem has stemmed from that in some way.

I've checked the caps, and none seem to be bad as far as I can tell, but I've included some pics anyway. If you need better ones, please let me know.

[SLK001]

Re: Vizio E400I-B2 powering on problem

Usually, when it does this, it means that there are bad LEDs in the backlight. A lot of VIZIOs will apply power to the LEDs, which will trigger a fault condition if there are bad LEDs on the strips, which then results in the TV shutting itself down. I've seen this condition more than once.

First thing, though, is to check the backside of the connector that connects the two boards together for fractured solder joints. These TVs have a bad habit of being shipped with broken joints.

[CapLeaker]

Re: Vizio E400I-B2 powering on problem

Hmm... the pictures are too blurry... but check the power on each string on the LED connector. It will tell you pretty quick whats going on. For now I am thinking bad LED's as well, or a bad joint on a connector etc.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

First thing, though, is to check the backside of the connector that connects the two boards together for fractured solder joints. These TVs have a bad habit of being shipped with broken joints.

Hmm, well I've checked the backside, and the solder joints "appear" pretty intact. I've included pics also, just in case I don't know what I'm talking about.

Hmm... the pictures are too blurry... but check the power on each string on the LED connector.

This is the first time I've ever worked with/on an LED TV, so I have absolutely no idea where/how to check that. Care to share any pointers on that, by chance?

[CapLeaker]

Re: Vizio E400I-B2 powering on problem

The 24V on the PSU go to the LED driver board. That is the green board in post #1, second picture, on top of the PSU. That board drives the backlight LED's.
There should be a connector with a bunch of red and black wires going to the LED strips. Each Red and Black wire power one string. For example: 4 red and black wires = 4 strings. You have to measure each string. It's a bit tricky, because you hafta power the TV on and measure the DC voltage of each string during the brief moment the backlights turn on. Post the result.

[SLK001]

Re: Vizio E400I-B2 powering on problem

Hmm, well I've checked the backside, and the solder joints "appear" pretty intact. I've included pics also, just in case I don't know what I'm talking about.

The joints look okay (but CapLeaker is correct in that your camera sucks).

I've seen this enough to know that you have bad LEDs in some of your strips. I have never been able to measure the voltages going to the strips because my meter can't settle fast enough.

You're going to have to remove the panel. Disconnect the panel PCB from the output of the TCON board. The connectors hold the ribbon cable via a plastic bar that snaps into place. Using your fingernail, unsnap the bar and disconnect both ribbon cables. The front bezel is held on by a combination of screws and molded in snaps. Whenever you handle the panel, use clean cotton gloves. Try not to touch the back side of the panel with your bare hands. Lay the TV on its back and remove the bezel. Once the panel is ready to remove, stand the entire TV on one of the narrow ends and tilt the TV forward so that the panel begins to fall forward. You just want the panel to fall far enough away from the chassis so that you can get your hands around the sides. Grasp the panel and lift it away and lean the panel against the wall as close to vertical as you can (5" away from the wall at the bottom and contacting the wall at the top). Just remember: THESE LCD PANELS CANNOT SUPPORT THEIR OWN WEIGHT. IF YOU TRY TO LIFT THE PANEL FROM THE CORNER, YOU WILL CRACK IT AND THAT IS THE END OF THE STORY FOR THIS TV!!!

Back to the chassis, lay it back down on its back. There will be some prismatic and diffuser pieces now visible. Mark an index mark one one corner and mark each sheet in order. Try to remove all the sheets as one (keeps things simple). These things are dust magnets, so prepare a place to lay them flat on clean cotton towels (do NOT place them on carpet without a towel underneath them). Now remove the main plexiglass diffuser, then the pure white background piece that covers the LEDs. Keep these parts CLEAN!!!

I don't know if you can test the LEDs in situ - if you can, then test the strips to find the bad one(s). Once you find a bad strip, unscrew it from the panel and use a hair dryer to soften the glue on the tape that holds it down as you slowly lift the strip off.

A note here: I have never opened this size of VIZIO, but I have repaired a few 47" TVs from the same series.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

First off, sorry for the delayed response. But I'm sure you guys know how the holidays can be at times, lol.

There should be a connector with a bunch of red and black wires going to the LED strips. Each Red and Black wire power one string. For example: 4 red and black wires = 4 strings. You have to measure each string. It's a bit tricky, because you hafta power the TV on and measure the DC voltage of each string during the brief moment the backlights turn on. Post the result.

Ok well, I'm just gonna assume that those set's of red/black wires, could instead equate to sets of "positive/negative" wires for my particular situation. Since this seems to be the wire array on my end, that you were referring to:


IF I'm correct, would that mean there is 5 different LED strings? And as for testing those, could I latch the ground onto the frame, or would it need to be on one of the negative wires?

The joints look okay (but CapLeaker is correct in that your camera sucks).

I've seen this enough to know that you have bad LEDs in some of your strips. I have never been able to measure the voltages going to the strips because my meter can't settle fast enough.

You're going to have to remove the panel. Disconnect the panel PCB from the output of the TCON board. The connectors hold the ribbon cable via a plastic bar that snaps into place. Using your fingernail, unsnap the bar and disconnect both ribbon cables. The front bezel is held on by a combination of screws and molded in snaps. Whenever you handle the panel, use clean cotton gloves. Try not to touch the back side of the panel with your bare hands. Lay the TV on its back and remove the bezel. Once the panel is ready to remove, stand the entire TV on one of the narrow ends and tilt the TV forward so that the panel begins to fall forward. You just want the panel to fall far enough away from the chassis so that you can get your hands around the sides. Grasp the panel and lift it away and lean the panel against the wall as close to vertical as you can (5" away from the wall at the bottom and contacting the wall at the top). Just remember: THESE LCD PANELS CANNOT SUPPORT THEIR OWN WEIGHT. IF YOU TRY TO LIFT THE PANEL FROM THE CORNER, YOU WILL CRACK IT AND THAT IS THE END OF THE STORY FOR THIS TV!!!

Back to the chassis, lay it back down on its back. There will be some prismatic and diffuser pieces now visible. Mark an index mark one one corner and mark each sheet in order. Try to remove all the sheets as one (keeps things simple). These things are dust magnets, so prepare a place to lay them flat on clean cotton towels (do NOT place them on carpet without a towel underneath them). Now remove the main plexiglass diffuser, then the pure white background piece that covers the LEDs. Keep these parts CLEAN!!!

I don't know if you can test the LEDs in situ - if you can, then test the strips to find the bad one(s). Once you find a bad strip, unscrew it from the panel and use a hair dryer to soften the glue on the tape that holds it down as you slowly lift the strip off.

A note here: I have never opened this size of VIZIO, but I have repaired a few 47" TVs from the same series.

When replacing LED's, do you have to replace the whole strip, or are you able to replace individual LED's? Also, can I use these latex gloves instead of cotton, should I end up needing to break it all open?

[budm]

Re: Vizio E400I-B2 powering on problem

Can we see the pictures of the whole back side of the TV so we can see how all the boards are connected together?

[SLK001]

Re: Vizio E400I-B2 powering on problem

When replacing LED's, do you have to replace the whole strip, or are you able to replace individual LED's?

You can replace individual LEDs.

Also, can I use these latex gloves instead of cotton, should I end up needing to break it all open?

You need gloves, because you do not want to transfer anything that you touch to the LCD screen. Cotton is the best for this, but as long as you keep the gloves clean, these may work okay.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

Can we see the pictures of the whole back side of the TV so we can see how all the boards are connected together?

You most certainly can! It's not the best resolution, but for what you're asking I THINK it should suffice. Please let me know if not, and I'll do better.

[CapLeaker]

Re: Vizio E400I-B2 powering on problem

Take a measurement on each LED string.

[budm]

Re: Vizio E400I-B2 powering on problem

Take the DCV reading pf those 5 black wires which are the Cathode returns for each of the LED string (there are 5 strings of LEDs).
You will put Black probe on the chasiss, red porbe on one of the 5 BLACK WIRE, turn on the TV and see the DCV reading, then turn off the TV and move the red probe to the next black wire and take the DCV reading, do that again on the other 3 black wires.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

Take the DCV reading of those 5 black wires which are the Cathode returns for each of the LED string (there are 5 strings of LEDs).
You will put Black probe on the chassis, red probe on one of the 5 BLACK WIRE, turn on the TV and see the DCV reading, then turn off the TV and move the red probe to the next black wire and take the DCV reading, do that again on the other 3 black wires.

Ok, following your directions exactly, here are my results:

Moving from the outside black wire to the innermost-

#1: 8.20
#2: 8.27
#3: 8.40
#4: 8.39
#5: 8.18

[CapLeaker]

Re: Vizio E400I-B2 powering on problem

8V DC? That can't be right. You have to measure these, while the backlight comes on for the 2 seconds before it turns off again. read post #5 again.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

8V DC? That can't be right. You have to measure these, while the backlight comes on for the 2 seconds before it turns off again. read post #5 again.

I did actually.

This was my process. I attached the black lead to the chassis, with a clamp (that even had rubber ends, not that that'd matter in this case), so that my hands could be free for holding the red lead and powering on TV at same time.

Then (with the wiring harnesses all attached) put the red lead on the back-side of the boards connector (aka, the metal post going from where each black wire connects to the motherboard. Then, with the red lead held there, I powered on the TV with my free hand. It would read just what I stated above, then go back down for a split second, and then back up to the same voltage. And I tested each twice, just to make sure.

Thoughts?

(I did exactly as he said in post #12, so if that's incorrect, please let me know)

[CapLeaker]

Re: Vizio E400I-B2 powering on problem

Sounds like there isn't a problem with the LED's themselves, rather a problem with the LED driver board seems more likely, or the main board isn't sending BL-on to turn on the LED's first place.

[budm]

Re: Vizio E400I-B2 powering on problem

What are the DCV for the Brown, Red, Orange, Yellow, and Green?
You need to do the reading of each pin the same way as you did on those black wires.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

Ok, so each and every wire (Brown, Red, Orange, Yellow, and Green), all read a solid 32.0, which seems a bit weird to me. But it could be right too, I suppose. Luckily one of you will know for sure, though~!

And just, you know, to make sure there's no human error on my end in regards to my meter.. I've included a screenie of my settings. So if anything's off, please let me know!

[budm]

Re: Vizio E400I-B2 powering on problem

That does not sound right with only 32VDC. You did leave black lead on the chassis and the red lead on the connectors and turn the TV and the Voltage only jump up to 32VDC, right?
What is the Voltage rating as printed on the cap TC2, or TC3, or TC 4?
Vizio 55.76N04.A01 (48.76N09.01M) LED Driver
http://www.shopjimmy.com/vizio-55-76...ed-driver.htm#
Pictures provided by shopjimmy.

[TheCockroach]

Re: Vizio E400I-B2 powering on problem

That does not sound right with only 32VDC. You did leave black lead on the chassis and the red lead on the connectors and turn the TV and the Voltage only jump up to 32VDC, right?
What is the Voltage rating as printed on the cap TC2, or TC3, or TC 4?

Hmmmm.. they're labeled as 50v 100uf caps, all 3 are.

And yes, I left black lead on the chassis and the red lead on the connectors and turn the TV on, and then then Voltage only jumped up to 32VDC (32VDC exactly, on all 5 leads)