Vizio VO47L FHDTV10A No display

[Beowulf]

Hello,
Problem details: TV turns on normally and lights up the vizio LED logo on the front but it doesn't show any signs of video. I tried connecting a video source (PS3, xbox etc) and play something to see If I could hear sound. I was not able to get any sound, although is unsure how I could perform the sound test accurately when I dont know what input the tv is currently set to. I did tried messing with the input button and also conecting the video source to all the inputs....










Anyway here is what I've found so far:

-On the inverter boards both caps, as circled in red, on each of the boards were bulged and I replaced them. I did a quick check on the transistors and they seem fine.

-On the Power supply board I found a bulged cap, as circled in red, and replaced it. The two inductors next to it are in bad shape leaving a very dark spot on the pcb. From the bottom there is delamination and some part of the board is lifted but the traces dont look bad. Anyway the PSU is providind all the output voltages as indicated on the output pins marked on the PCB.

This is as far as I'm able to get. Could this be inverters problems and how can I check?

Thanks

[jetadm123]

Re: Vizio VO47L FHDTV10A No display

On your last photo, have you tried measuring the output voltages at the wiring harnesses?

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

Yeah they're all good.

[tom66]

Re: Vizio VO47L FHDTV10A No display

When those caps go bad, they sometimes kill the controller IC and/or MOSFETs.

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

Tom66 you mean on the inverter board?

[tom66]

Re: Vizio VO47L FHDTV10A No display

Yes, sorry if I wasn't clear.

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

Thanks I'll check it out.

[cliff_hootarski]

Re: Vizio VO47L FHDTV10A No display

Did you try the old flashlight trick?
Turn on the TV. Shine a flashlight on the LCD screen and see if you see any video. You'll have to look closely, and sometimes this is inconclusive because it is usually very hard to see the video.

[MisterD]

Re: Vizio VO47L FHDTV10A No display

when you can't see the inputs on the screen wait at least 7 seconds before you push input button again do this each time, make sure you have something hooked up and playing like a dvd player, I had one model Vizio take that long to cycle between inputs.
When you say no Video do you mean the screen doesn't light up at all?

[cliff_hootarski]

Re: Vizio VO47L FHDTV10A No display

I have worked on about 4 of these sets. The capacitor you replaced is almost always bad. That leads to the caps on the inverters going bad and
then the controller IC and Mosfets. If that's not enough, the main boards go
out with alarming frequency. Main boards on Ebay run $115 and up. Main board repair services start at about $50, however they only fix certain problems on the board.

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

I tried the flashlight trick and I'll try it again after your encouragement.
Yeah what I mean is that the screen doesn't light up at all. I'll try tweaking the imputs while playing a dvd again and wait 7 seconds.
The mosfets are those two sets of four next to each cap? I have the cap wizard can I test them on board?
Also the driver IC I dont have an oscilloscope yet any other way to check it out?
Thanks

[budm]

Re: Vizio VO47L FHDTV10A No display

Can I see closed up pictures of the inverter connector areas?

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

Sure, hope these are good.

[budm]

Re: Vizio VO47L FHDTV10A No display

So are you getting >3 at pin 12 (ON/OFF), also 24v on the fuse?

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

ON THE MASTER BOARD:
-I'm getting the 24v on the connector side of the fuse, and .9 on the other side of the fuse.
- On the connector, pin 12, I'm getting 3.23v. And 24v on pin1 etc.

ON THE SLAVE BOARD:
-I'm getting the 24v on both sides of the fuse.
-On the connector, pin 12, I'm getting 0v (there's no connection). And 24v on pin1 etc.

With the tv turned on.

[budm]

Re: Vizio VO47L FHDTV10A No display

That voltage is not right on the fuse for the master board then, it has blown fuse. You need to check all the MOSFETs on the master inveter board for short.

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

Yeah I just found that the fuse is blown indeed although I'd swore I checked them and found them good so I'm wondering if I messed it up whole taking the voltage readings from the connector .
The mosfets all read identical on both boards so I'm assuming they're right.
Should I still try to desolder them difficult smt soldered mosfets and confirm they're good?

[Beowulf]

Re: Vizio VO47L FHDTV10A No display

Took the four mosfets from one side and two from the other from the master board and tested them, none looked shorted.

[tom66]

Re: Vizio VO47L FHDTV10A No display

In which case replace the fuse and see if it blows again.

[budm]

Re: Vizio VO47L FHDTV10A No display

I would replace those two caps on both master and slave board, and install a new fuses (you can use pigtail fuse or picoii fuse, or use fuse and fuse holder) and try it out.