Vizio 42" LCD VW42LHDTV10A Will Not Turn On

[MisterD]

The Standby Vizio Light is on but the TV will not turn on, I have checked voltages on the power supply board pin connectors and only have the 5v Standby Voltage, When holding down the power on button I have checked Pin 1 which is the PSON and the 3.3 volts is Not present, so the Power Supply will not turn on, which means the 12v and 24v are also not present. I have checked both small fuses on the Main Board and they are both good. Now I need to know the next step in troubleshooting, I read about the dummy load test for the PS Board but I don't think that will work without the 3.3v at PSON. Any help is appreciated.

[tom66]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

This video may be applicable to your problem:
http://www.youtube.com/watch?v=cNFzBJELFoU&feature=plcp

Test ALL regulators, not just the one in the video.

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

That was helpful and interesting and could possibly lead in the right direction, although my problem is different than what he had going on, I need to find out where the 3.3 v for PSON is supplied from and why I don't have it. Thanks!

[tom66]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

I know that bad LDOs cause lots of problems for Vizios - sometimes powering on with lines on screen, with backlight or not at all (sometimes logo changes colour, other times not.) So it would be worth checking anyway as Vizio are plagued with regulator problems.

[Don Umphrey]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

I have a Vizio model vo320e 32inch TV which has no picture, or sound and has a black screen . The Vizio name logo is orange in stand by and white when turned on . The only side button that will respond is the on/off button. When turned on there is a blue lite coming from each board. The blue lite on the power supply/inverter back lite board stays lite longer (several seconds) before going out. The blue lite coming from the main board goes out much quicker. I have taken voltage reading at the wire harness plug connectors where the power supply board connect to the main board. The reading at the three 5volt pins and three 12volt pins were good. At the pin marked on/off I get a voltage reading of .1 volts in the off position and 2.87 volts is the on position. I have also have taken voltage reading at the large capacitor which lays on it side on the power supply/ inverter board. I got 167 volts turned off and 390 volts turned on. A visual look at the boards through a magnify glass shows no signs of bulging caps or signs of any over heated components. When talking with Vizio they said I would need a new LCD screen with back lite. Do you think I am getting a right answer ? I hate the thought of throwing the TV out if it was something less expensive to repair. Thank you Don

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

I checked voltages on some LDO's although the set will not power on, On the Mainboard U33, U8, and U2 all have normal input output voltages but U7 and U9 have 3.3 v input but zero v output on one and only .01v output on the other. does anyone know if all these regulators should have normal working voltages with tv plugged in and the power off?
Thanks!

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

i know that bad ldos cause lots of problems for vizios - sometimes powering on with lines on screen, with backlight or not at all (sometimes logo changes colour, other times not.) so it would be worth checking anyway as vizio are plagued with regulator problems.

1

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

"but U7 and U9 have 3.3 v input but zero v output on one and only .01v output " Can we see the pictures and the P/N?

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Here's both U7 and U9 U7 is AMC1117 F0722F and U9 is K1117S15 726

[tom66]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

So the voltage on the rightmost pin is 3.3V?

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

So the voltage on the rightmost pin is 3.3V?

Yes, The rightmost pin is 3.3v, middle pin is 2.01v, left pin is 0v and larger pin is 2.01v that's on U9

0n U7 rightmost pin is 3.3v, middle pin is .8v, left pin is .01 v and larger pin is also.8 v

[tom66]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

It is very unusual for both regulators to fail so there might be another fault.

Do they get hot at all after 5-10 mins in the not turning on mode? Just lightly touch them with your finger and if it is hot enough to be painful, there is a problem. If they're just warm, probably OK.

Then turn the set off and test the resistance across the middle pin to the chassis of the TV. You should read a few hundred ohms, maybe more.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

The output pin is the middle pin.
"0n U7 (AMC1117 F0722F) rightmost pin is 3.3v, middle pin is .8v, left pin is .01 v and larger pin is also.8 v"
This one does not look right. Check the resistance reading between middle pin an ground.

U9 is K1117S15 726 looks like a 1.5V regulator, so middle pin is at 2V. Does not look right.
I will look up the spec.

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Set unplugged, U7 middle pin to chassis ground is 97.3 ohms and U9 middle pin to chassis ground is 337 ohms. touched both regulators lightly after set plugged in 5-10 minutes they are both cool.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

OK from looking at the picture, U9 has a resistor between Left pin (Ground pin) and circuit ground to raise the output voltage from 1.5V to 2V.
U7 has resistor betwenn the ADJ pin and circuit ground and another resistor between ADJ pin and the output pin. Can you tell me the value as printed on those two resistors, I cannot see them clearly due to the dark shadow. They look like R50, R51. I need to know the value an which one is connected to the left pin and the circuit ground.

[tom66]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

I don't think they have a value printed. They are 0402 size and only 0603 upwards are printed.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

If not, he will just have to measure them so Ican calculate the output voltage.
"0n U7 rightmost pin is 3.3v, middle pin is .8v, left pin is .01 v and larger pin is also.8 v"
Base on this reading, it does not look good since minimum out put will be 1.25V. U7 is an adjustable 1117 LDO, you canot have output less than the ref voltage.

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

OK from looking at the picture, U9 has a resistor between Left pin (Ground pin) and circuit ground to raise the output voltage from 1.5V to 2V.
U7 has resistor betwenn the ADJ pin and circuit ground and another resistor between ADJ pin and the output pin. Can you tell me the value as printed on those two resistors, I cannot see them clearly due to the dark shadow. They look like R50, R51. I need to know the value an which one is connected to the left pin and the circuit ground.

Sorry but there is nothing printed on those very small resistors.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

That is OK, at this point I think it is pretty safe to say that U7 is bad since the output voltage cannot not be less than 1.25V.

[MisterD]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

as measured in circuit R50=95 Ohms and R51=2.3 Ohms, I can't tell which one goes to the left pin but could be R50, I'm not sure.