Dead Vizio VL 420M

[Tayninh55]

This tv was thought to be hit by lightning or a power surge. When plugged in, it shows nothing, no yellow or white logo. I was hoping it was a blown fuze, so I checked it for continuity and it looks ok. I then turned the board over and at the upper left hand corner of the board, put the blk lead on the ground terminal and the red lead on the N terminal, and it shows 124V. I moved the red lead to the L terminal and it shows nothing. I then moved the red lead up to the left side to the fuse, and again, nothing. There is a solder joint "between" the two prongs of the plug, (between N & L) but I don't know what it is for. Shouldn't I have the same voltage (124V) at the left side of the fuse and if so, what do you think is the problem? Keep think I'm checking something the wrong way!
Thanks for any suggestions!

[budm]

Re: Dead Vizio VL 420M

The AC inlet has LINE pin, NEUTRAL pin, and Safety GND pin (middle pin).
When check AC in the primary side, you will check the incoming AC on Line and Netral all the way to the two inner pins of the bridge rectiifer.
Then when you check the Voltage in the primary side circuit, you will use the negative leg of the main filter cap as the GND ref for the meter.
So did you check to see if you have 120VAC at the two inner pins of the bridge rectifier?
Did you check and see if you have about 160VDC on the two legs of the main filter cap?
Please also upload good clear pictures of the whole back side of the TV so we can how all the boards are connected together.

[Tayninh55]

Re: Dead Vizio VL 420M

Ok,,,,,,,,,,I'll take a look at it, not positive I know exactly what you're saying. Here are the pics of the other board.

[budm]

Re: Dead Vizio VL 420M

We need the whole backside of the TV to see how many boards are used in your TV and how they are connected together.

[Tayninh55]

Re: Dead Vizio VL 420M

Ok,,,,,I was going to "be smart" and find that rectifier bridge myself. I see lots of diodes but not what I'm supposed to be finding. I give up, where is it? I did check for voltage at the big 120mf capacitor. When I measured across the leads I got 171V there. As soon as you show me the Ret Bridge, I'll check the voltage there

[freakaftr8]

Re: Dead Vizio VL 420M

What are you getting for standby 5v going to mainboard?

[Tayninh55]

Re: Dead Vizio VL 420M

Ok,,,,,here is the "whole back" of the set.

[Tayninh55]

Re: Dead Vizio VL 420M

Freak,,,,,,,,,,,where do I check for "stand by" voltage?

[CapLeaker]

Re: Dead Vizio VL 420M

Ok,,,,,I was going to "be smart" and find that rectifier bridge myself. I see lots of diodes but not what I'm supposed to be finding. I give up, where is it? I did check for voltage at the big 120mf capacitor. When I measured across the leads I got 171V there. As soon as you show me the Ret Bridge, I'll check the voltage there

The bridge rectifier is the black transistor looking thingy with 4 legs right next to the filter cap mounted to the heat sink. Since you measured 171v at the filter cap, tells me that the bridge rectifier and the fuse is o.k.

The standby voltage 5v is always there on the power supply. Look at the power supply secondaries. There are a bunch of wires going from the power supply to the main board. Look at the connector on the power supply, there should be a pinout printed on there, maybe post a pic of that.

[budm]

Re: Dead Vizio VL 420M

Check the DC Voltages of those two white connectors (black probe on the chassis) pins when TV is plugged in but power switch is NOT activated, and when the power switch is activated.
There should be labels for each pin of those connectors, make sure to list them all.
http://www.shopjimmy.com/vizio-0500-...upply-unit.htm

[Tayninh55]

Re: Dead Vizio VL 420M

OK Capleaker and Budm,,,,,,,,I think I might have gotten lucky! The picture of the board printout where the ribbon connectors connect the two boards is attached. And thank you for telling me to check the voltage on those pins on the ribbon connector. I checked the voltage on the 12 pin connector with THE POWER ON and wrote down each number,,,,,,,,then went to the 6 pin ribbon connector and started checking. When I got to the 5th pin on that ribbon (which is marked on/off on the board) I thought I really screwed up. As I touched this pin with my red lead, a small grayish looking chip to the left of the pin and near halfway across the board, LITE UP WITH A BRIGHT BLUE LIGHT (almost like a gas torch burning) and I THOUGHT "DAMN, I'VE SHORTED SOMETHING OUT". Then I noticed that the TV was on. It came on the instant I connected the meter between the pin and the chassis ground. The screen lite up and the "No Signal" messages flashed on the screen. Then, it went back off, with the exception of the Logo at the bottom (Which didn't light at all before). It is yellow when off,,,,,and when I push the ON button, it turns white,,,,,,but the screen doesn't light up now.

[Tayninh55]

Re: Dead Vizio VL 420M

When you look at the picture of the bottom of the power board,,,,the pins for the ribbon connector runs at the top, from left to right. I started with the number one pin as being the far left on each ribbon. Here are the voltages with the set in the OFF position (yellow logo) on the 12 pin ribbon. Pins 1, 2, & 3 have 5.25V, pins 4, 5, 6, 7, 8, 9, 10, & 11 have zero Volts and #12 showed .51V

With the power ON: Pins 1, 2,, & 3 have 5.18V, pins 4, 5, 6, 7, 8, 9, 10, & 11 have zero Volts and #12 shows .58

Now the 6 pin ribbon with the power OFF (yellow logo) Pins 1, 2, 3, 4, & 6 show zero volts,,,,,,pin #5 shows .10 volts.

The 6 pin ribbon with the power ON (white logo) Pins 1, & 2 show .05V, pin 3 shows .04V, pin 4 shows zero volts, pin 5 shows 2.21V and pin 6 shows Zero volts. They were all measured on the 20v meter scale.

[CapLeaker]

Re: Dead Vizio VL 420M

Do you see the no signal screen with the TV on and you shine a flashlight at it? The 6 pin ribbon is for the backlight. What you did was that you turned the backlight on. Hmm on your measurement on the 12 pin ribbon with TV on, where there should be 12v there is none?

[Tayninh55]

Re: Dead Vizio VL 420M

Cap, I don't know,,,,,,,,but I'll try it and see right now. How did that turn the back light on? I turned the tv on and off a couple times with an active screen,,,,,,then it just stopped. The logo is still changing colors (that's more than it was doing before), but the screen is still black. That little chip that lit up is marked on the attached photo (I hope), what is that?

[budm]

Re: Dead Vizio VL 420M

You should post each name of the pin and the voltage readings next to that pins, it will make it much easier to know what is each.
For example
Pin +5V, TV OFF = xxV, TV ON = xxV

"There should be labels for each pin of those connectors, make sure to list them all"
as requested in post 10.
Remember that we do not have the TV and the boards in front of us to check.

"With the power ON: Pins 1, 2,, & 3 have 5.18V, pins 4, 5, 6, 7, 8, 9, 10, & 11 have zero Volts and #12 shows .58

Now the 6 pin ribbon with the power OFF (yellow logo) Pins 1, 2, 3, 4, & 6 show zero volts,,,,,,pin #5 shows .10 volts.

The 6 pin ribbon with the power ON (white logo) Pins 1, & 2 show .05V, pin 3 shows .04V, pin 4 shows zero volts, pin 5 shows 2.21V and pin 6 shows Zero volts. They were all measured on the 20v meter scale."

I have no idea what the function of pin 1,2,3...are. there are names on those pins.

[Tayninh55]

Re: Dead Vizio VL 420M

Well, I just pushed the on button,,,,,,,,,logo went from yellow to white,,,,,,,turned the lights out and shinned a flash light on the screen. Can't see a sign of anything, just all dark. Here I thought I was close. I tried moving the ribbon connectors a little bit, but that didn't do anything either.

[Tayninh55]

Re: Dead Vizio VL 420M

Ok,,,,,,,,,,,,,,,,,if that's what you want:

The 12 pin ribbon, left to right:

Pin Number On Off

1 5.18 5.25
2 5.18 5.25
3 5.18 5.25
4 0 0
5 0 0
6 0 0
7 0 0
8 0 0
9 0 0
10 0 0
11 0 0
12 .58 .51

Six Pin Connector, left to right

1 .05 0
2 .05 0
3 .04 0
4 0 0
5 2.21 .10
6 0 0

Yes, When I looked at the markings on the edge of the board, I saw where several were supposed to be 12V, but the numbers above is what was on the meter.

[Tayninh55]

Re: Dead Vizio VL 420M

Ok,,,,,,,,,,,,,,,,,if that's what you want:

The 12 pin ribbon, left to right:

Pin Number On Off

1 +5vsb 5.18 5.25
2 +5vsb 5.18 5.25
3 +5vsb 5.18 5.25
4 SGND 0 0
5 SGND 0 0
6 SGND 0 0
7 SGND 0 0
8 SGND 0 0
9 12V 0 0
10 12V 0 0
11 12V 0 0
12 PS_ON-LAMP-STATUS .58 .51

Six Pin Connector, left to right

1 PS_ON-LAMP-STATUS .05 0
2 PS_ON-LAMP-STATUS .05 0
3 DCR .04 0
4 VBRA 0 0
5 ON_OFF INVERTER 2.21 .10
6 BLANK 0 0

Yes, When I looked at the markings on the edge of the board, I saw where several were supposed to be 12V, but the numbers above is what was on the meter. Bye the time I write my post and submit it,,,,,,it tells me I'm not authorized to do this and that I have to "refresh and log on". I go to the top of the page and can see that I'm STILL LOGGED ON, but I refresh, LOSE MY POST,,,,and have to rewrite it again!

[Tayninh55]

Re: Dead Vizio VL 420M

I also had it spaced out in my reply,,,,,,,,,,,,,,,,,,,when i submit,,,,,,,,,,,,the columns all go together

[budm]

Re: Dead Vizio VL 420M

Well the main board is not sending the PS_ON (last pin on the 12-pin connector).
And these what the pins are:
1 +5vsb 5.18 5.25
2 +5vsb 5.18 5.25
3 +5vsb 5.18 5.25
4 SGND 0 0
5 SGND 0 0
6 SGND 0 0
7 SGND 0 0
8 SGND 0 0
9 12V 0 0
10 12V 0 0
11 12V 0 0
12 PS_ON .58 .51

Six Pin Connector, left to right

1 ACD .05 0
2 LAMP-STATUS .05 0
3 DCR .04 0
4 VBRA 0 0
5 ON_OFF INVERTER 2.21 .10
6 DIM 0 0

Since PS_ON is not present, the main power supply will not be turned on.