VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no picture

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

yeah all zeros on that side

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

dang i wish this page would auto refresh when u post or something...

[budm]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

OK the MOSFET is not being turned on, the control pin 2 and pin 4 should have close to 0Vdc when TV is turned on, pin 1 and 3 are getting the 12V feeding them OK.
What you can do to test is to put jumper wire between the 4 pins on the left and the positive leg of that cap CE64 to see if you will get the picture.
Show me the picture of the jumper wire in place before you plug the TV in, I want to make sure you do it correctly.

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

Ok wait...do I solder this in place? And to all 4 pins?

[budm]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

Those 4 left pins (pin 5~8) are connecting together to one large copper pad, so just solder 1 wire to that pad, then the other end of the wire will be connected to the positive leg of the cap CE64 which is next to that MOSFET.

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

Ok I get it

[budm]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

Show me the picture so I can see that you did it correctly before you apply the power.

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

Will do. Thanks!

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

ok soldering is done. i didnt see a single pad that all 4 of those pins went to like u said...but i guess i made my own with solder

u might not be able to see it so good in the pictures but i made sure no solder is touching anything but those 4 pins, and for the capacitor too just on that one positive pin

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

hmm..when u said pad did u mean the lighter colored green pcb ?

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

oh i see now and those 6 holes.. so those 4 pins might as well just be one pin then?

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

cant wait to test it out...i wont turn it on till you review the pics tho!

[budm]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

OK! not great clean job, but that will do for now.

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

success!!! you are the man!
that totally was the problem!
i still would like to understand completely though... what exactly that chip does, and why it was not doing it, and how jumping this connection affects the operation of the tv?

is this a permanent fix or do i have to replace that chip for any reason? and if this works then why did i need that chip there in the first place??

so awesome to have fixed my first big tv with your help. without your help i would never have figured all this out, and now i know a lot more about electronics in general. i have some other TV's that im going to get right to work on as well and i hope you and the others here would like to help me with them as well!

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

i included the pic of my soldering iron to let u all know why my solder joints were messy. this is a really cheap and abused soldering iron.

[budm]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

"is this a permanent fix " No, this is to verify that the T-CON and other video processing functions are OK. The MOSFET is OK, but the Gate is not getting the turn on signal.
What we did is bypassing the switch, the MOSFET is being used as a switch by the control signal feeding into pin 2 and 4, that signal is stuck high as we had measure the voltage around 12V on pin 2 & 4.
You can use it as is but when TV is in standby, the 12V will still be applied to the T-CON all the time instead of being off, the only time 12V will not be present is when TV is switched off.
The GATE pin 2 and 4 look like it is being drive by transistor Q26, there should be about 0.6V between B and E as you can see the label next to it, see if it does have 0.6V

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

ok wait... when you say GATE and MOSFET are you talking about the same chip? the one with 4 pins to the left (toward j30) and 4 pins to the right (away from j30)

pin 2 and 4 would be the pins on the side closer to j30 right?

you said
" that signal is stuck high as we had measure the voltage around 12V on pin 2 & 4. "

but we measured those earlier and they were all zero...the 12v were only on the right side which would be pins 4-8, right?

[vinceroger69]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

q26 is the small 3 legged transistor to the left of the ic you soldered the wires too test between b and e its marked on the board.

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

oh wait i get it the gate is Q26
and yeah with the tv turned on i get .6v across b and e

[triplefour]

Re: VIZIO V037L FHDTV20A powers up, backlight on, sound works, buttons work, no pict

it looks like the output of the gate goes into the mosfet somewhere but i cant exactly see which pin... it would be one of the pins on the right though, yeah? the voltage coming out of the gate is only .3, but those pins were measured to be 11.95 and 12.05 ... what does the .3 do ?