Vizio VP422 won't turn on.

[Malachi]

Re: Vizio VP422 won't turn on.

or remove both and solder a wire link on the underside of the pcb.

That seems easier. Could I use the wires I have cut off from capacitors I've replaced?
I said I keep everything.
I could probably unsolder one end of the jumpers and push it through, then bridge the connection from the underside.

[dick_barton]

Re: Vizio VP422 won't turn on.

You would need to ensure that you remove both jumpers away from the board before you solder your replacement links on the underside. If the cut off of the cap legs or resitor legs are about the same diameter (or thicker) as the ones you remove then no problem.

[Malachi]

Re: Vizio VP422 won't turn on.

I took dicks suggestion. When I measure the resistance now that budm asked for, it starts at about 4Mohm and then drops. Do I have to wait till meter stops?

[dick_barton]

Re: Vizio VP422 won't turn on.

That's good. That isolates on side of the circuit as being OK. Now measure the resistance between U8301 where budm has circled in red, to Point B

[Malachi]

Re: Vizio VP422 won't turn on.

That's good. That isolates on side of the circuit as being OK. Now measure the resistance between U8301 where budm has circled in red, to Point B

I did. I posted the results one post above.
Unless I'm confused. Measured between point A and B from budm' picture.

[dick_barton]

Re: Vizio VP422 won't turn on.

Basically it's to measure the resistance of the circuit with the jumpers removed.
1st reading between Point B and one side of the jumper
2nd reading between Point B and the other side of the jumper

[Malachi]

Re: Vizio VP422 won't turn on.

If the MOSFETs are not shown as shorts then remove IC U8301, easier way will be removing the two jumpers wires for the GND return of the IC.

I measured according to this picture. Meter stopped at 280kohms.

[dick_barton]

Re: Vizio VP422 won't turn on.

Just taken another look at the picture of the underside of the board and I've marked the wrong set of jumpers when talking about removing / cutting them.

Give me some time to re-read through the posts to see what budm was suggesting so I can get back on track.

[dick_barton]

Re: Vizio VP422 won't turn on.

I have had a second read through the posts and everything is correct so ignore my last post. I was starting to confuse myself.

If after removing the links you no longer have 0.5 ohm as in the test carried out in Post74 then U8301 is short circuit and will need to be replaced.

[Malachi]

Re: Vizio VP422 won't turn on.

So I should be able to replace U8301 and that will solve the psu problem?
The numbers on that are 80183 then under that MR4030.

[dick_barton]

Re: Vizio VP422 won't turn on.

Hopefully it should bring back your supplies. It would be worth your while checking the components around it.

The part is available from Mouser

Mouser Part No:
627-MR4030

[Malachi]

Re: Vizio VP422 won't turn on.

Hopefully it should bring back your supplies. It would be worth your while checking the components around it.

The part is available from Mouser

Mouser Part No:
627-MR4030

Thanks. I saw that on mouser already.
eBay has then from China for $5 total. I'd take a year to get here. Lol.
Wife isn't happy already that I have this laying flat on the floor and a 60" lg next to it.
I'll have to decide what to do.
Thank you guys for the help.

[budm]

Re: Vizio VP422 won't turn on.

Glad to hear that you are able to narrow it down to that SMPS IC by removing those to GND return jumpers, now you have some idea how we go about isolating the circuit to locate the shorts.
113 posts!
BTW, make sure that the old jumpers are not touching the heatsink.

[Malachi]

Re: Vizio VP422 won't turn on.

I didn't remove the jumpers budm. I cut the trace on the bottom of the board.
Much easier, I can lay some solder on it or jump it with a wire.
My question now is, is that component the only shorted one.
I know what we did but not really how that tells you guys what is shorted.

I'm a 50 year old learning new things. At my age, my parents could barely turn the tv's and vcr on. Lol

[budm]

Re: Vizio VP422 won't turn on.

I am 62, so you are not that old to me.

[Malachi]

Re: Vizio VP422 won't turn on.

Are you a repairman by profession?

[budm]

Re: Vizio VP422 won't turn on.

Are you a repairman by profession?

Only during the college year long time ago, I am just doing this for funs and knowledges (I do the Volunteer works one day a week for non-profit Electronics recycle since 1995) and get to see what not to design into the products.
I am lucky to have this volunteer works to help fixing electronics and kept them from landfill.

[Malachi]

Re: Vizio VP422 won't turn on.

I would love to do that also.

[dick_barton]

Re: Vizio VP422 won't turn on.

I didn't remove the jumpers budm. I cut the trace on the bottom of the board.
Much easier, I can lay some solder on it or jump it with a wire.
My question now is, is that component the only shorted one.
I know what we did but not really how that tells you guys what is shorted.
l

Budm traced the circuit out for you.
From the large capacitors which holds the rectified AC (now as DC) coming in from the mains supply, he traced it to the fuse and from the fuse to a transformer winding.
The other end of the transformer winding is connected to the IC.
By lifting the ground from the IC any short circuit in the IC to ground was now broken.
You no longer measure 0.5 ohms so the IC must have been shorted to ground.
The IC if you look at the data sheet has an internal Mosfet and it is this which has probably gone short circuit. The 0.5 Ohms measured is probably the transformer winding resistance through the shorted Mosfet (IC) to ground.

[Malachi]

Re: Vizio VP422 won't turn on.

Budm traced the circuit out for you.
From the large capacitors which holds the rectified AC (now as DC) coming in from the mains supply.
From the capacitor he traced it to the fuse and from the fuse to a transformer winding.
The other end of the transformer winding is connected to the IC.
By lifting the ground from the IC any short circuit in the IC to ground was now broken.
You no longer measure 0.5 ohms so the IC must have been shorted to ground.
The IC if you look at the data sheet has an internal Mosfet and it is this which has probably gone short circuit. The 0.5 Ohms measured is probably the transformer winding resistance through the shorted Mosfet (IC) to ground.

Ok. I wish that was is English. Lol