Vizio VW46L Power Supply - no output

[DakotaKid]

Waiting on parts for another one I am working on so I cracked this one open and found the power supply is not putting out any voltage, including standby. Therefore, no lights, no power button, nothing. Power supply is Darfon B094-101 4H.B0940.011/C1 with an Amtran label with Viz part number 0500-408-0530. 120V incoming is good and the 6.3A glass fuse is 0.00 Ohms so good continuity there. No damage is apparent on any of the caps or any components on top or bottom of the board. No burn marks, scorch marks or blown apart ICs that I can see. There is voltage at various points on the board, around 57VDC seems most common but not sure that is meaningful at this point. The inverters are built into the board.

The attached pictures show the top and bottom of the board plus some of the key components such as FETs and ICs. So, where do I start? Thanks in advance.

[XmouseX]

Re: Vizio VW46L Power Supply - no output

Fuses? What about any of the resistors. Sometimes they are just dark and not noticeably burnt at first glance. Interesting that you are getting voltage in other locations...

[retiredcaps]

Re: Vizio VW46L Power Supply - no output

So, where do I start?

For no 5V standby, I like to start at the big filter cap and make sure it is 165V DC (careful high voltage). If present, then I move onto the SMPS chip (US201).

Datasheet

http://pdf1.alldatasheet.com/datashe...CE3B1565J.html

says pin 7 is your VCC and pin 8 is your GND. What is the DC voltage on pin 7? Is it steady or fluctuating? It looks like it requires 18V to start (page 16).

You can also check the DC voltage on startup cap that is tied to pin 7.

[DakotaKid]

Re: Vizio VW46L Power Supply - no output

I was doing some checking and found one of the 3569 power transistors is shorted on all three legs. In the picture it is the one furthest from the board edge of the two that are near the large (damper?) diodes. it feeds the 24V inverter transformer circuit. I will follow up on the posts you made while I was away. Thanks.

The big cap reads 96VDC but very steady. US201 reads -54VDC at every pin except 6 which is a few mv and fluctuating. There also seems to be a -55VDC bias somewhere. When I ground on a chassis screw on the board I get 96VDC at the large cap, when I ground at any heat sink it reads 152VDC. Same for US201. All of the pins that read -54VDC read near 0 relative to the heat sink.

Should I go ahead and remove the the shorted resistor and take readings again to see if that makes a difference?

[beard60]

Re: Vizio VW46L Power Supply - no output

I have this same model with same issues. i replaced two bad caps but no luck.the logo goes from Orange to white but no backlight. any help would be appreciated

[budm]

Re: Vizio VW46L Power Supply - no output

I have this same model with same issues. i replaced two bad caps but no luck.the logo goes from Orange to white but no backlight. any help would be appreciated

Pictures of YOUR board will help.
What DCV do you get at the power supply connector that goes to the main board? List the pin name and pin number and follow by the DCV reading of each pin so we can see what you have.

[beard60]

Re: Vizio VW46L Power Supply - no output

I need to get a multimeter to read them. I fixed 2 bad caps and a broken wire near the 450v capacitor on power board.

[beard60]

Re: Vizio VW46L Power Supply - no output

when the TV is turned on there is no backlight, the vizio logo goes from Orange to white and while it does that there is a squeak/screech noise that come from the speakers for half a second then stops. tv will not turn off by button either.

[dick_barton]

Re: Vizio VW46L Power Supply - no output

Start from the very beginning withthe basic checks.
What are the voltages in standby/out of standby at the various connectors highlighted.
If you could label them something like below would make for easy reading.

CN4
Pin No. Label - Stby - On
Pin1 (VCC) 0, 5V
Pin2 (FB) 0, 1.4V

and the same for the other 2 connectors

[beard60]

Re: Vizio VW46L Power Supply - no output

ok so i replaced both main board and power board and all is working just 3 lines on left side of screen blue,red,green lines

[budm]

Re: Vizio VW46L Power Supply - no output

That is the panel problem.

[beard60]

Re: Vizio VW46L Power Supply - no output

any way to fix this? if i push around outside of pannel it gives horizontal line flickering. but parallel lines stay there. bad pannel?,tab bonds?

[CapLeaker]

Re: Vizio VW46L Power Supply - no output

if it doesn't go away by pressing lightly on the tab bonds (open up the TV to access the tab bonds), you either have to live with it or toss it.