Vizio SV470XVT1A LCD no power

[Sevenqi]

Vizio SV470XVT1A 47 inch LCD TV, no poweer at all, Power Board is DPS-379AP, I plugged it in the power supply and checked the output for 24V,12V,5V, all no output, the fuse is good.

Which part I need to check for now ? Anyone can provide the servie manual for this power board ?

Thanks

[PlainBill]

Re: Vizio SV470XVT1A LCD no power

Vizio SV470XVT1A 47 inch LCD TV, no poweer at all, Power Board is DPS-379AP, I plugged it in the power supply and checked the output for 24V,12V,5V, all no output, the fuse is good.

Which part I need to check for now ? Anyone can provide the servie manual for this power board ?

Thanks

Service manuals are non-existent for most power supplies. There are a couple of voltages to check. One possible culprit is the start-up cap.

Pictures of the top and bottom of the supply will help us help you. This site has a limit of 2000 x 2000 pixels, so try to get ones just under that. Attach them using 'Manage Attachments' - under the text entry area.

PlainBill

[Sevenqi]

Re: Vizio SV470XVT1A LCD no power

This is the photo:

[PlainBill]

Re: Vizio SV470XVT1A LCD no power

This is the photo:

Oy!!! So many problems I'm not sure where to start.

1. Just to the left of center is a capacitor laying on it's side, under the heat sink. The top appears to be bulging.

2. On the near edge of the board, about center is a small electrolytic cap. This is PROBABLY the startup cap. A failure of that cap results in no output voltages.

3. I had asked for pictures of both top and bottom of the power supply. The SMPS controllers are probably on the bottom of the board.

4. Pictures from directly above the supply are much better than severely inclined shots.

5. The higher the resolution, the better. It helps immensely if I can say "Check D211" rather than downloading a picture, using Paint to circle a component, and uploading it.

I've attached two pictures as an example of what I like to see.

PlainBill

[Sevenqi]

Re: Vizio SV470XVT1A LCD no power

Thank you very muc PlainBill !

This is the picture I took.

The big cap C804 always has DC 170V even if I unplug the power.
The cap mentioned in 1. is not actually bulging.
All the polar capacitor look good, not bulge.
Still can't figure out which is start-up cap, the one(CY1) in blue color ?

[Sevenqi]

Re: Vizio SV470XVT1A LCD no power

More pictures:

[PlainBill]

Re: Vizio SV470XVT1A LCD no power

Thank you very muc PlainBill !

This is the picture I took.

The big cap C804 always has DC 170V even if I unplug the power.
The cap mentioned in 1. is not actually bulging.
All the polar capacitor look good, not bulge.
Still can't figure out which is start-up cap, the one(CY1) in blue color ?

That is a VERY important clue. Even if the startup cap were bad, I would expect to see the large cap discharge fairly quickly. The startup cap is the small electrolytic cap anchored with glue - C903?? It's next to the transformer with the windings covered in yellow tape.

On the bottom of the board there is an 8 pin IC near the startup cap, IC900. That is most likely the SMPS controller. What is the part number?

PlainBill

[Sevenqi]

Re: Vizio SV470XVT1A LCD no power

I suspected the R841 was open, this Rigistor provides the DC power to the folowing circuits, because one end has 170V, the other end has 0V. It's very difficult to open the heatsink to check the value, I would add another one at the board bottom, but don't know what vaule is good.

[Sevenqi]

Re: Vizio SV470XVT1A LCD no power

I took out the Cap c903, c914, they all good.
So I had to took out the heatsink,all 5 big transistors had to screw out (not a good design!).
Then I saw two resistors are burn, R841(ohm unknown) ,R919(0.75 ohm), then I guessed the transistros might also burn, I took out Q806(1NK60Z), all foots were open circuit, and Q905(3N80C), all foots were short circuit.
Now my problem is the R841, one side was burn and no word can be seen, the other side is 916, an idea what 916 means, is it the value of ohm ?

[PlainBill]

Re: Vizio SV470XVT1A LCD no power

I took out the Cap c903, c914, they all good.
So I had to took out the heatsink,all 5 big transistors had to screw out (not a good design!).
Then I saw two resistors are burn, R841(ohm unknown) ,R919(0.75 ohm), then I guessed the transistros might also burn, I took out Q806(1NK60Z), all foots were open circuit, and Q905(3N80C), all foots were short circuit.
Now my problem is the R841, one side was burn and no word can be seen, the other side is 916, an idea what 916 means, is it the value of ohm ?

Well done locating the problems. 916 is not a resistance value - if 6 was a multiplier, that would make it a 91 Megohm resistor.

The only suggestion I can make is that while Badcaps Forum may be the best repair forum, it isn't the only one. Locating others and asking the same question seems to be the only option.

PlainBill

[Sevenqi]

Re: Vizio SV470XVT1A LCD no power

Well done locating the problems. 916 is not a resistance value - if 6 was a multiplier, that would make it a 91 Megohm resistor.

The only suggestion I can make is that while Badcaps Forum may be the best repair forum, it isn't the only one. Locating others and asking the same question seems to be the only option.

PlainBill

Thank you for your help, PlainBill !

[Plasmaman]

Re: Vizio SV470XVT1A LCD no power

Working on the same model tv, same symptoms. No power outputs at all, start-up caps and others check ok on the cap wizard. R841 also blown. R841 value shows 0.1 ohms on this power supply DPS-379AP A Rev01. The bottom of R841 was blown apart but I could still read the value on the top side.

[1a2s3d4f]

Re: Vizio SV470XVT1A LCD no power

I also has the same issue. Please let me know what is the value of R919 and R841. 91Mega ohm is not seem right.

thanks

[sunnyman]

Re: Vizio SV470XVT1A LCD no power

Hi everyone I have a vizio tv sv470xvtt1a picture is good but no sound
i try all inputs but no good please help Thank you























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