Vizio VA19L Won't Power On

[sysvr4]

Hello,

I just found this forum while searching for ideas on how to repair this little Vizio TV I have. Please excuse me, but I have no TV repair experience, although I do own solder and desolder tools (and a multimeter), so I'm willing to give it a go Any help solving this is greatly appreciated...

My daughter was playing around this TV the other day and caught a cord which sent it tumbling to the floor. My fault for not securing it properly... anyway, since that drop it won't power on. There's no standby light on either, but honestly, I'm not 100% sure it even has one.

So I took the thing apart today and started fiddling around with the multimeter on the power supply board. I don't know much more than when I started, but here's what little I do know:

- The fuse is good
- 110V is reaching the board
- The power traces its way around to the large horizontal capacitor where I have 110V on one leg and 0V on the other (and across it)
- There is 0V on standby and all the 5V and 12V pads by the bundle going over to the mobo

None of the capacitors look bulged to me, though I understand that's not a guarantee. Unfortunately, I don't have a capacitance tester.

That's all I got. Like I said, I'm a newbie, so be gentle Thanks in advance!

[Mr Bill]

Re: Vizio VA19L Won't Power On

Check and see if you have about 165v dc on the large cap with the power supply plugged in. Put the negative probe on the striped side of the cap and the positive probe on the other. Did the screen get cracked when it tumbled down?

[sysvr4]

Re: Vizio VA19L Won't Power On

Thanks for the response Mr Bill!

I just checked as you described and I get 178V DC across that cap with the power plugged in.

Amazingly, the TV suffered no physical damage at all that I can discern, either external or internal. My best guess at this point is that either the power or HDMI cords yanked on something internally when it fell, causing this problem, but that's just speculation at this point...

Thanks again!

[Mr Bill]

Re: Vizio VA19L Won't Power On

Will you post a photo of the connector legend that i put a square around? Post a picture of the main board too. See if there are any fuses on the main board and see if they are good.

[drpj23]

Re: Vizio VA19L Won't Power On

In the cases that I have had fallen electronics not work, it has been cracks in the pcb. Perhaps not in the power supply but on the main. And I am surprised as well the LCD did not crack.

[sysvr4]

Re: Vizio VA19L Won't Power On

Why certainly!

I don't see any fuses on the main board, but I may well have missed one. Let me know if any of you guys spot one...

Also, let me know if I can post any other pictures that would be helpful. Thanks again!

[sysvr4]

Re: Vizio VA19L Won't Power On

In the cases that I have had fallen electronics not work, it has been cracks in the pcb. Perhaps not in the power supply but on the main. And I am surprised as well the LCD did not crack.

Is there a way I can easily discern if the power supply is doing its job? In other words, how could I narrow down at least which board has the problem?

[budm]

Re: Vizio VA19L Won't Power On

Are you getting 12v and 5V at the connector? This power supply is an always on power supply, you should have the voltage at the connector without truning on the power switch, the minute you plug in the power you should have those DC voltages.

[sysvr4]

Re: Vizio VA19L Won't Power On

Are you getting 12v and 5V at the connector? This power supply is an always on power supply, you should have the voltage at the connector without truning on the power switch, the minute you plug in the power you should have those DC voltages.

That's a negative. No DC voltage at all on any of the 5V or 12V pads, nor on standby.

That narrow us down to the power supply?

[drpj23]

Re: Vizio VA19L Won't Power On

Pretty much. Does anything change when you disconnect the connectors (main and the two backlight wires?

[budm]

Re: Vizio VA19L Won't Power On

That yellow circuit board material is real easy to crack.
Can I get good closed up pictures of the bottom side of the power board, take pictures in 1/4 section of the board so I can easily zoom in the traces?

[sysvr4]

Re: Vizio VA19L Won't Power On

Pretty much. Does anything change when you disconnect the connectors (main and the two backlight wires?

Nope, still 0V on everything.

Also, I don't know if this is helpful or not, but I noted the following on these two components...

Green - 4 pins starting from north to south:

0V, 110V, 0V, 110V

Purple - 5 pins on the "west" side, starting north to south:

110V, 110V, 110V, 0V, 0V

On the "east" side, no voltage (AC or DC) on any of the pins.

[budm]

Re: Vizio VA19L Won't Power On

The bridge rectifier (green) is ok since you are getting the 170vdc on the large cap ok.
the transformer is getting the power but does not look like it is switching, that is why i need to see bottom side of the board.
By the, when you measure the voltages on the primary side, you need to use the negative leg of the large cap as a ground ref, do not use the chassis as the ground ref when work in the primary side.

[retiredcaps]

Re: Vizio VA19L Won't Power On

What is the DC voltage across the startup cap (C920)?

[sysvr4]

Re: Vizio VA19L Won't Power On

That yellow circuit board material is real easy to crack.
Can I get good closed up pictures of the bottom side of the power board, take pictures in 1/4 section of the board so I can easily zoom in the traces?

Sure thing, here ya go... I'm posting these offsite because they are 18 megapixel shots. That should allow zooming down to the molecular level

Full Back

Full Front

Back quarter 1

Back quarter 2

Back quarter 3

Back quarter 4

[sysvr4]

Re: Vizio VA19L Won't Power On

By the, when you measure the voltages on the primary side, you need to use the negative leg of the large cap as a ground ref, do not use the chassis as the ground ref when work in the primary side.

You know it's bad when you have to tell a guy that to ensure you're getting accurate measurements. You know it's worse when he actually didn't know to do that and your suggestion makes a difference.

Ok, remeasuring the 5V and 12V pads by the connector using the 907 capacitor negative, I get roughly 86VDC across each of them. Given the labels, that voltage seems way off to me, but at this point, it's obvious I don't know what the heck I'm talking about so I'll leave that for you guys to say...

Also, the standby pin had about .1 or .2 VDC measuring that same way.

That help?

[sysvr4]

Re: Vizio VA19L Won't Power On

What is the DC voltage across the startup cap (C920)?

I get 0V on that one.

And let me take this opportunity to say what a fantastic resource this board is. You guys don't know me from Adam, and so many folks are willing to take their time to help walk a guy like me through this... that's amazing! Thank you all very much...

Truth be told, I'm starting to see why you guys enjoy this so much. I've even been on Amazon looking for good beginning electronics books the last few days. What a cool skill to have... anyway, thanks again!

[budm]

Re: Vizio VA19L Won't Power On

"Ok, remeasuring the 5V and 12V pads " these voltages are in the secondary side, you will need to use the chassis ground as a ref ground point.
There are two sections to the power supply board, the Primary (hot) and the Secondary (Cold) side which is isolated from the Primary (deadly side where youe have 120VAC applied to the Primary side of the circuits).
You should have this board powered throgh the GFI outlet to protect yourself in case you body makes contact with the primary side.

[retiredcaps]

Re: Vizio VA19L Won't Power On

I'm posting these offsite because they are 18 megapixel shots.

18 megapixel is not required. We can easily get by on quality in focus shots with 2000x2000 resolution and 2MB.

[retiredcaps]

Re: Vizio VA19L Won't Power On

See if Q901 is shorted between G-D, G-S, D-S.