Vizio VW42L FHDTV10A (Newbie Post)

[PohTayToez]

Long time lurker, first time poster here. I've been fixing electronics for years, mainly computers, cell phones, and iPods. I've dabbled in some monitor/TV repair, but while I have no trouble replacing any sort of component I never properly learned how to diagnose them (outside of spotting visible bad caps)

Anyway, I have a Vizio TV I'm working on. The status light goes from amber to white when you hit the power, but otherwise does nothing (no backlight, vid or sound). I've read about a dozen or so threads from here on this model and it seems like it's a common problem with many possible causes.

So first things first, here are the pictures:
Power Board
Main Board
T-Con Board
Inverter Board
Inverter Board (Close Up)

What I've tested so far:

Power Board:
Outputs going to inverter:
24V = 25.26v
A = 5.05v
B = 3.33v
Outputs going to main board:
PSON = 3.19v
12V = 11.83v
5V = 5.16v
A = 3.35v
B = 5.07v

T-Con Board:
Fuse tested good

Inverter Board:
Fuse tested good

Main Board:
Both fuses tested good
Tested all the voltage regulators I could find:
U20 = 2.76v/1.25v (VI/VO)
U19 = 2.81v/1.25v
U15 = 2.98v/1.25v
U22 = 3.02v/1.26v
U44 = 2.63v/1.25v
U17 = 2.97v/1.26v
U21 = 2.51v/1.26v
U16 = 10.84v/5.07v

Oh and there are no visibly failed capacitors.

[retiredcaps]

Re: Vizio VW42L FHDTV10A (Newbie Post)

Tested all the voltage regulators I could find:

We have no idea if the regulators are good or not without knowing

1) the part number of the regulator
2) the reading on all 3 pins

My sig file below shows the preferred easy to read format for reporting the above.

[DakotaKid]

Re: Vizio VW42L FHDTV10A (Newbie Post)

In addition, are you sure you don't have a VW42LF with "F" at the end rather then VW42L in your title? I've worked on some VW42L and they have a similar but very different main board than your picture. VW42L is 720p, VW42LF is 1080p so it is pretty easy to figure out which you have in addition to the model on the back label. The VW42L schematic (which I have) is no use for your troubleshooting. I don't have schematic for VW42LF.

I've worked on a few VW42L's and with the symptoms you describe I always, in my cases, found it to be a faulty LDO regulator, usually U33 if I remember right. Once the output of one regulator is off spec then all bets are off on how the board will act because other inputs rely on outputs of these LDO's and Vizio has a history of board design and/or component failures with these LDO's in the VW and VX series.

Complete speculation but I do believe you'll find that one of those LDO's is out of voltage spec either from it failing so something supplying voltage to it. But, as retiredcaps said, none of us can really help without more details on the parts and more thorough readings of all 3 pins.

[Dgtech]

Re: Vizio VW42L FHDTV10A (Newbie Post)

The one inverter board that you posted a picture of has 3 bad caps. They are bloated. Please post the picture of the other inverter board, if there is one on the other side.

You will also need to check the FETs and the fuse on the inverter board(s).

[PohTayToez]

Re: Vizio VW42L FHDTV10A (Newbie Post)

Hey, I just wanted to say thanks and sorry for not giving good information the first time around. I can't believe I didn't notice the capacitors bulging on the inverter too. I'll order some replacements right away. I also went ahead and redid all of my readings properly:

Power Board:
Outputs going to inverter:
24V = 25.26v
SGND = .02v
A = 3.35v
B = 5.07v
Outputs going to main board:
PSON = 3.19v
12V = 11.84v
SGND = .00v
5V = 5.17v
A = 3.35v
B = 5.07v

T-Con Board:
Fuse tested good

Inverter Board:
Fuse tested good

Main Board:
Both fuses tested good
Voltage Regulators:
U20
C11
1084
0745DL
Pin 1 = .55v
Pin 2 = 1.81v
Pin 3 = 3.32v
========================================
U19
C11
1084
0745DL
Pin 1 = 1.26v
Pin 2 = 2.52v
Pin 3 = 5.07v
========================================
U15
C11
1084
0745DL
Pin 1 = 2.09v
Pin 2 = 3.35v
Pin 3 = 5.07v
========================================
U22
AMC1117
F0748F
Pin 1 = 2.10v
Pin 2 = 3.36v
Pin 3 = 5.12v
========================================
U21
AMC1117
F0748F
Pin 1 = .00v
Pin 2 = 1.26v
Pin 3 = 2.51v
========================================
U17
AMC1117
F0748F
Pin 1 = 2.10v
Pin 2 = 3.37v
Pin 3 = 5.07v
========================================
U44
K022
G9117
Pin 1 = 8.42v
Pin 2 = 9.68v
Pin 3 =10.83v
========================================
U16
7805CT
RNT707G
Pin 1 = 10.82v
Pin 2 = .00v
Pin 3 = 5.06v
========================================

The one inverter board that you posted a picture of has 3 bad caps. They are bloated. Please post the picture of the other inverter board, if there is one on the other side.

You will also need to check the FETs and the fuse on the inverter board(s).

There is only one inverter board. (Picture of all the boards for reference)

I did check the fuse on the one board. Is there a guide here on identifying and testing FETs?

In addition, are you sure you don't have a VW42LF with "F" at the end rather then VW42L in your title? I've worked on some VW42L and they have a similar but very different main board than your picture. VW42L is 720p, VW42LF is 1080p so it is pretty easy to figure out which you have in addition to the model on the back label. The VW42L schematic (which I have) is no use for your troubleshooting. I don't have schematic for VW42LF.

I've worked on a few VW42L's and with the symptoms you describe I always, in my cases, found it to be a faulty LDO regulator, usually U33 if I remember right. Once the output of one regulator is off spec then all bets are off on how the board will act because other inputs rely on outputs of these LDO's and Vizio has a history of board design and/or component failures with these LDO's in the VW and VX series.

Complete speculation but I do believe you'll find that one of those LDO's is out of voltage spec either from it failing so something supplying voltage to it. But, as retiredcaps said, none of us can really help without more details on the parts and more thorough readings of all 3 pins.

(Picture of back label)

It is definitely not a VW42LF, which I read about in other threads here. U33 on my main board is an 8 pin chip.

[tom66]

Re: Vizio VW42L FHDTV10A (Newbie Post)

U20
C11
1084
0745DL
Pin 1 = 1.55v
Pin 2 = 1.81v
Pin 3 = 3.32v

This regulator is suspect. Please re-test it. If you get the same results it may be failed.

[PohTayToez]

Re: Vizio VW42L FHDTV10A (Newbie Post)

Sorry, my mistake. The correct reading on pin one is .55v not 1.55v

[tom66]

Re: Vizio VW42L FHDTV10A (Newbie Post)

In which case the regulator is functioning correctly.

A = 3.35v
B = 5.07v

When the logo is orange (TV is in standby) what do these read?
When the TV logo is white does pressing the power button make it go orange?

I suspect your inverter is faulty. Everything is working but the backlight is not showing so you'll see no image.

[PohTayToez]

Re: Vizio VW42L FHDTV10A (Newbie Post)

In which case the regulator is functioning correctly.

A = 3.35v
B = 5.07v

When the logo is orange (TV is in standby) what do these read?

In standby A reads .20v and B reads .02v.

When the TV logo is white does pressing the power button make it go orange?

Yes.

I suspect your inverter is faulty. Everything is working but the backlight is not showing so you'll see no image.

I am suspecting this as well. I will try powering it and shining a light on the screen to see if I get an image.

[tom66]

Re: Vizio VW42L FHDTV10A (Newbie Post)

This definitely leans towards inverter fault.

Note some LCD panels don't let you see an image with a flashlight, it's due to their design.

[PohTayToez]

Re: Vizio VW42L FHDTV10A (Newbie Post)

This definitely leans towards inverter fault.

Note some LCD panels don't let you see an image with a flashlight, it's due to their design.

Yeah, I'm not able to see anything but I'll go ahead with replacing the caps on the inverter and go from there.

[johnboy1313]

Re: Vizio VW42L FHDTV10A (Newbie Post)

I had the 47" version of this set come across my bench. I couldn't get the amber Vizio logo to go white. The issue turned out to be bad caps on the inverter and PSU and a bad fuse on the inverter as well. I replaced these components and the set fired right up. I kinda skimmed through your posts so I apologize if I missed this. Did you check fuse F1 next to pin 1 of CN1 on the inverter?

[PohTayToez]

Re: Vizio VW42L FHDTV10A (Newbie Post)

I had the 47" version of this set come across my bench. I couldn't get the amber Vizio logo to go white. The issue turned out to be bad caps on the inverter and PSU and a bad fuse on the inverter as well. I replaced these components and the set fired right up. I kinda skimmed through your posts so I apologize if I missed this. Did you check fuse F1 next to pin 1 of CN1 on the inverter?

Yes, I found and checked one fuse on every board and two on the input board.

[PohTayToez]

Re: Vizio VW42L FHDTV10A (Newbie Post)

Just wanted to follow up on this in case someone else has the same problem -- it was the capacitors on the inverter and nothing else. Thanks for the help! I feel silly for not being able to determine the problem myself.

[johnboy1313]

Re: Vizio VW42L FHDTV10A (Newbie Post)

It happens. Good job saving it.

[logonsys]

Re: Vizio VW42L FHDTV10A (Newbie Post)

I know this is an older post but can I ask a quick question and hope for a response? First off, I was out here about 3 years ago with my Vizio VW426 no pic, no sound, and you guys were able to help me. It was a bad main board. Although I can replace a board, I don't have the eyesight or steady hand to do board level repairs. Anyway, the pic and sound are going out again intermittently. Seems after it has warmed up. The remote still works, can power on and off with it. I have already replaced the main board again but this time didn't fix it. So, my question is, power supply, inverter, or T-Con? Keeping in mind I get no picture and no sound, light stays white. I can power off, wait a few minutes, power back on and it will work for anywhere from 5 minutes to an hour. What would be the best guess at what board to replace next? Any help would be greatly appreciated. Thank you!

[johnboy1313]

Re: Vizio VW42L FHDTV10A (Newbie Post)

The fact that both sound and pic are cutting out makes me think power supply. If it was just pic, the T-con would be suspect. If it was just sound, main or power supply. Are there any bloated caps on the PSU?

[logonsys]

Re: Vizio VW42L FHDTV10A (Newbie Post)

Thanks for the fast response! No bloated caps that I could see. I also noticed I have greying/darkening around the edges of the TV when it's working. Could it be that the backlight bulbs are going?
I'll try to get some pics but the camera on my phone does not have great resolution.

[Dgtech]

Re: Vizio VW42L FHDTV10A (Newbie Post)

I worked on more vizio vw42l tvs than any other set . In most sets the inverters, one or the other was the problem. Usually if just the sound goes...i would suspect the slave inverter. If both...then the master is bad. Do you have a way to check voltages and resistances? If so... with powrr off...check the resistaces across each of the four fets on each inverter and post your findings.

[logonsys]

Re: Vizio VW42L FHDTV10A (Newbie Post)

This tv has only one inverter board to the left of the main (when looking from the open back of the set). I have a volt meter so I'll check those tonight while I'm waiting for my tile to set/dry. Right in the middle of a kitchen remodel. Nothing like juggling several unrelated projects!