I have a Vizio P42HDTV that won't turn on. I believe the main and sub power boards are ok, as all the voltages check out.
How can I tell whether the turn on issue is from the power supply versus the main (DTV) board?
The unit's power light comes on when I plug it in, but pressing the power button does not cause the led to cycle to green, nor do the main power relays click.
Please check the U29 8 pin little surface mount mosfet it has this letters > FDS4935 > > In this part inputs 13.2 volts which is ok for the near 12 vdc but it > outputs 1.250 vdc i am 100% sure that this is all the problem > > check it out, and tell me if you´re agree with me > > On this output pin it feeds the audio Ic, the 7809 and the tuner side board > which needs de 12vdc too and its getting only the 5vdc part > > what do ya think?? > > Richard
Please check the U29 8 pin little surface mount mosfet it has this letters > FDS4935 > > In this part inputs 13.2 volts which is ok for the near 12 vdc but it > outputs 1.250 vdc i am 100% sure that this is all the problem > > check it out, and tell me if you´re agree with me > > On this output pin it feeds the audio Ic, the 7809 and the tuner side board > which needs de 12vdc too and its getting only the 5vdc part > > what do ya think?? > > Richard
Please check the U29 8 pin little surface mount mosfet it has this letters > FDS4935 > > In this part inputs 13.2 volts which is ok for the near 12 vdc but it > outputs 1.250 vdc i am 100% sure that this is all the problem > > check it out, and tell me if you´re agree with me > > On this output pin it feeds the audio Ic, the 7809 and the tuner side board > which needs de 12vdc too and its getting only the 5vdc part > > what do ya think?? > > Richard
Hi same problem, but which component is the problem?? i cant buy a new dtv board ill try ti fix it, but which caps are the faultys?? pls help
I think i got it!!!
Please check the U29 8 pin little surface mount mosfet it has this
letters
> FDS4935
>
> In this part inputs 13.2 volts which is ok for the near 12 vdc but
it
> outputs 1.250 vdc i am 100% sure that this is all the problem
>
> check it out, and tell me if you´re agree with me
>
> On this output pin it feeds the audio Ic, the 7809 and the tuner side
board
> which needs de 12vdc too and its getting only the 5vdc part
>
> what do ya think??
>
> Richard
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Relays are the first big clue, triggered by the 5 & 12v supply you should be able to trace back using a dmm and see if you have both of those voltages present... The lead coming from the smps to the y-sus board is a good start. On a Vizio I believe the voltages are listed per pin right on the board...
If you had any kind of relay sound then you could suspect the y-sustain or z-sustain board or something else. With the relays being silent I'd strongly suspect the power supply.
Bill
Could very well be thermal affected - and somewhere in the cause and symptom it's likely to include being some caps will need to be replaced. Don't rule out the sustain boards - they could very well be loading down the supply and cause these very symptoms. You might try unplugging first the x-sus from the supply and try to power the unit. If it comes up normally (picture messed up of course) powers okay has audio then try testing the components on the x-sus. Then try the same thing with the y-sus. At this point you'll need to take out the schematics and mesaure some test points to isolate the problem. While you're at it, might as well get out the esr meter and some mist and check on a few caps - might help narrow down the area too..
Good Luck!
Bill
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Hi Bill, thanks for the info. I did some more diagnosing and came up with the following:
http://www.forumsigs.com/img.cfm?img=387...
- When first plugged in, the relays do click.
- After I press the power button, no clicking.
- There is a switch on the main power board, that is labeled Auto/Normal. If I switch it to Auto, the relays click and I can see the screen illuminate. Its still black, but you can tell it came on. No menu or video signal displayed.
- If its unplugged for awhile and I plug it in, I can sometimes press the power button and the screen will come on with regular video for about 30 seconds. It will then click back off and pressing the power button won't do anything else.
I almost wonder if its thermally related.
Here's a link to a photo I took.
I labeled the parts. Do you think this is the DTV board? I think the Y/Z sustain boards are ok, since the image looks fine when it does come on.
I can't find a cap that's bad, but using this manual -
nationalservicealliance.com/visio/VIZIO-P42HDTV10A.pdf
I discovered most of the input voltages to the voltage regulators are not correct. The 7809 should have at least 10V on pin 1 to regulate down to 9V on pin3. My input was 1.26V, way too low.
Here are the readings for my board -
J1 All 5V lines good
J1 All 12V lines good
U4 3.3V output good
U5 1.8V output good
U6 0V output and 1.26V input. This is the 7809.
U7 0V output
U13 0.31V
U14 0.31V
J2 5V on all lines
J7 Should read 3V or higher on the buttons (Power, volume, etc)
I noticed that when my TV turned on I had the correct voltages on the buttons. When it wasn't working, the button voltages were under a volt. I never could catch the voltage at one of the regulators at the same time the button voltages worked.
Vancebaldwin sells the board for $145'ish including shipping. They have a core charge of $60'ish. Unless I can get ahold of a schematic, it may be easier to just buy another board.
I'd be happy to swap info with someone directly or via phone if they'd like.
Please check the U29 8 pin little surface mount mosfet it has this
letters
> FDS4935
>
> In this part inputs 13.2 volts which is ok for the near 12 vdc but
it
> outputs 1.250 vdc i am 100% sure that this is all the problem
>
> check it out, and tell me if you´re agree with me
>
> On this output pin it feeds the audio Ic, the 7809 and the tuner side
board
> which needs de 12vdc too and its getting only the 5vdc part
>
> what do ya think??
>
> Richard
where is that board with pin 8 u29
wont turn on p42 vizio
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