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

[vinceroger69]

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

too be honest as you have done all these tests now i would buy a replacement mainboard there a resonable price imo.

[budm]

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

OK, remove the connector J8 for the LVDS cable (where the cable is connected between the main board and the T-CON), then check the DC voltage on pin 30 (left most pin) of J8 to see what you have.

[triplefour]

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

happy to do more tests before spending any money or throwing anything away

on the j8 connector of the mainboard i disconnected the lvds cable and tested pin 30 which read zero. pin 29, 28 and 27 were also zero... some other pins were 1.2 or 1.25

but yea pin 30 is definitely zero.
what does that tell us?

[triplefour]

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

also how do you know its called J8? do u have a decent service manual for this board? i cant find schematics for it, and it doesnt say J8 anywhere near the connector...

[triplefour]

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

oh wait it does say j8 on it but i could only see that after removing the cable. still my first question remains, how did u know its J8?

[budm]

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

"how did u know its J8" from looking at the board and know what the connector should be going by the pictures, work on lots of electronics for 40 years.
Since you are getting a little voltage, it means the switched MOSFET that is turned by the main board to allow the 12V to be fed to the T-CON board may be bad or it is being driven correctly.
Right now I really need good clear pictures around pin 30 to see where the trace goes to, I can see it is connected to the Ferrite bead, another end of the Ferrite bead goes some where that I cannot see.
These are some of the pictures of what I work on for fun and knowledge.
http://s807.photobucket.com/user/bud...?sort=3&page=1

[triplefour]

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

lol nice kitty! u got me i was expecting to see some crazy electronics!

[budm]

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

On the left pane you will see the list of make and models: for example
http://s807.photobucket.com/user/bud...?sort=3&page=1

[triplefour]

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

ok heres the pics. lemme know if i didnt quite capture the mood, ill take some more.

[budm]

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

OK, I think I see that switched MOSFET now, it is the u29 (8-pin device).
Please read the P/N as printed on top of that MOSFET.

[triplefour]

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

oh cool i see youve fixed a lot of vizios. i imagine cause theyre cheap they break a lot? it must feel good to know youve saved so many things from going to the dump. and teaching other people how to do the same! how many TV's have you repaired yourself, and how many have been repaired with your help on this forum?

[budm]

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

Probably in the 1000's, I have been fixing them when they were using tubes!

[triplefour]

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

oh man the lettering is so small i couldnt even read it clearly with a magnifying glass. i had to use my cameras soom feature and the magnifying glass and i can just start to be able to read it but im still unclear on a few numbers

mx 12G or mx 120?
25L32050?2I

[triplefour]

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

ok i used my friends phone to get a better picture...apparently his camera beats mine by quite some margin.
u can clearly read the numbers now

[triplefour]

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

Mx-12g
25l3205dm2i
3a512200
taiwan
??0736

[triplefour]

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

cant seem to find the datasheet for this ....

[triplefour]

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

am i looking for a datasheet for a mx-12g?
or for 25l3205dm2i?

or do i have to search for both?

[budm]

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

OK, just to be sure, check the resistance between the positive leg of that lytic cap CE65 (the positive leg of this cap is connected to pin 30 of J8 through the Ferrite beads) and the top left pin of the IC. From the way it is connected looking at the traces to this IC, it may be the one for supplying the voltage to the T-CON, seems to be some kind of memory chip.

[triplefour]

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

with the multimeter in the 1000's range it reads 797 ... i took this reading with the power off. should it have been on?

[budm]

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

No, TV should be unplugged. So it does not have direct connection from pin 30 of J8 to that IC. Then we need to locate that MOSFET, it should be close to that J8 pin 30. Right now I am not seeing it.
BTW, any time when you do resistance testing, what ever you work on should have power removed. You will have power applied when you do the voltage testing.