Vizio VP422 won't turn on.

[dick_barton]

Re: Vizio VP422 won't turn on.

Hello Budm, I think I may have things backwards. Re-reading the posts #9 the PS_ON is 4.8V when the mainboard is disconnected.
It may have to be taken low not high as I've suggested to activate the other supplies.
Your thoughts please.

[Malachi]

Re: Vizio VP422 won't turn on.

Both fuses were good when I first started, that's the first thing I always check. It was the only thing I knew how to do when I started doing this.
Now F8201 is blown.
I just replaced it.

[budm]

Re: Vizio VP422 won't turn on.

I think so too that is the case for these Plasma power supply board is active low for PS-ON, and active HIGH for Vs I believe. I think there are many threads for this board on B.C.
https://www.badcaps.net/forum/search...archid=6381299
Blown fuse is then another problem to solve.

[Malachi]

Re: Vizio VP422 won't turn on.

Did you hear the two relays click when using the resistor to force on?
You also need command signals on the CN8002: VS_ON, RELAY_S???

I get 5.1v on those 2 budm.

[budm]

Re: Vizio VP422 won't turn on.

https://www.badcaps.net/forum/showth...o+VP422HDTV10A

Post 9.

[Malachi]

Re: Vizio VP422 won't turn on.

I guess it's time to take the psu out and check the voltage on the caps that dick suggested?

[budm]

Re: Vizio VP422 won't turn on.

See post 25.

[Malachi]

Re: Vizio VP422 won't turn on.

I read that thread budm but my Vizio logo never turns white.
I did a forum search before posting. I also get a lot less Voltage reading than others with the same model in other threads?

Did I do the resister thing wrong?

[Malachi]

Re: Vizio VP422 won't turn on.

Bad Ysus?

[Malachi]

Re: Vizio VP422 won't turn on.

See post 9 of that thread? I don't have any of those voltages.
I can't turn the tv on, so voltages stay the same.

[Malachi]

Re: Vizio VP422 won't turn on.

So there's definately no change when you connect 5VSB to PS_ON.

What is the voltage across the large capacitors C8103 & C8104. Its on the hot side of the mains supply so be very careful. Use your meter set to 600V and measure across the two pins of each of the capacitors.

I took the psu out of the tv. Laying upside down on a piece of cardboard. Plugged it in and measured each capacitor, voltage steadily climbing. After a few minutes I had less than 0.2V. Unless I'm reading my meter wrong.

[Malachi]

Re: Vizio VP422 won't turn on.

The capacitance is about 446uf on each, in circuit.
Fuse F8201 blew again.

[dick_barton]

Re: Vizio VP422 won't turn on.

That explains why you had no voltage on the caps. Why is the fuse is blowing? Can you see anything amiss on the board because that was not your original problem.

[Malachi]

Re: Vizio VP422 won't turn on.

I couldn't tell anything visually unusual.

[Malachi]

Re: Vizio VP422 won't turn on.

Receey, help me diagnose this psu before I start throwing parts at it.
What would make the fuse blow.
Also what kind of fuses are these? It's 4a 250v. I know there are slow blow and fast blow.
How do you tell the difference?

[Malachi]

Re: Vizio VP422 won't turn on.

I checked some of the 3 legged components that are screwed to the heat sinks. With my meter in diode mode.
With the diodes, when I touch the two outer legs the meter beeps. When touching the middle one and an outside one, it doesn't beep.

I also tested other 3 legged ones I'm not sure what they are called.
They are labeled Q8101, Q8102, Q8103, Q8201 and Q8202 none of them beep. This is all in circuit.

[budm]

Re: Vizio VP422 won't turn on.

That fuse feeds many parts.

http://www.shopjimmy.com/vizio-0940-...-pdp42-09.htm#

Pictures provided by shopjimmy.

[Malachi]

Re: Vizio VP422 won't turn on.

But I can't keep replacing them with out figuring out why the blow.
I had already checked shopjimmy. It's the first place I go.
What kind of fuse is that that I listed? I can buy a dozen. Lol
I did trace where the fuse goes to in the back but don't really know what to look for.

[budm]

Re: Vizio VP422 won't turn on.

'But I can't keep replacing them with out figuring out why the blow.'
But you already find the shorted out components? Which one?

'They are labeled Q8191, Q8102, Q8103, Q8201 and Q8202 none of them beep"
BTW, the meter will beep even if the resistance is as high as 100 Ohms on some meter. That is why I use Ohm mode to look for shorts or very low Ohm reading.

[Malachi]

Re: Vizio VP422 won't turn on.

So that means they are shorted?
What are those? Can I buy them from digikey?