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

[triplefour]

a friend of mine gave me this TV.
its a VIZIO V037L FHDTV20A
serial number: LSAFNAK1704932

when i plug in the power, i get the amber lighting up the VIZIO logo
when i turn it on the logo turns to white.
a few seconds later the backlight of the screen kicks in
but its just a lit up black screen.
i cant see a menu or anything.
i plugged in a N64 to test the sound and buttons.
i am able to switch to the correct source using the input button on the side of the TV.
i can hear mario kart coming out of the speakers
but i cant see any mario kart on the screen
the TV does not power off by itself, i can leave it on like this for quite a while.
so it seems like a lot of the TV is working properly, but im just getting no image!
i took the back cover off of it and started looking around.
i could not see any caps that looked suspicious.
nothing was bulging or leaking.
my guts tell me it cant be the power board because it powers up just fine.
and my guts tell me it cant be the inverter board because the backlight is nice and bright.
so that only leaves the mainboard, right?
i can only see 3 boards right now...is there a 4th hidden somewhere?
is there a TCON board?
im totally new to this but i have been reading around and watching some
youtube videos.
i am a computer scientist by degree and a computer technician by trade.
i have done some minor soldering here and there.
the other week i fixed one of my monitors by ordering a capacitor kit and replacing all the caps, so i know i can do that just fine.
thing is this doesnt appear to be bad caps :/
i have a decent multimeter but nothing fancy.
can someone point me in the right direction? what should i test to make sure its the motherboard before i try to replace/repair it?

thank you for your time. i hope my pictures and description is adequate!

[johnboy1313]

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

Check the voltage regulators on the main board.

https://www.badcaps.net/forum/showth...999#post300999

[triplefour]

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

i will do this and report my findings

[triplefour]

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

hmm ok i was reading the post u linked to but i got stuck here

"
4) Report them like below along with the part number (include all lines on the IC) of the IC. Don't report "they all tested good". About once every 2 weeks, we get someone who reports that only to find out they did the arithmetic wrong or mis-interpreted the results. So report all the readings.

U100 -> pcb designation
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
"

i have read those lines over and over again and looked at the pictures and i cant make head or tails of what im exactly supposed to do...

the voltage regulator is the little black thing with a tab (north) and 3 or more pins on the other side...right?

but what is an IC? it just starts talking about IC and i have no idea what that is.
(noob status)
i mean im pretty sure it stands for integrated circuit but even if thats true, thats all i know!

i mean i guess i get that pin 1 thru 3 are from left to right and i just measure the voltages and report but what all this business:
U100 -> pcb designation
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC

the picture is pretty blurry and i cant find it saying u100 or as1117-33 on any of those chips (maybe it does but i cant see it)

so um.. maybe ill read it a few more times and it will come to me...

[triplefour]

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

also i cant see in the datasheet for the 11117-33 where it explains what each of the 3pins are. i do see where the suffix -33 denotes a 3.3 volt output. i am deducting from the tutorial that the middle pin is the output, pin1 is just 0 cause its a fixed regulator, and pin3 is the input? is it like that for all voltage regulators?

still dont understand this line1 of the ic business..and what does u100->pcb designation mean??

[triplefour]

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

im just gonna take pictures of each one and label them with the volts on each pin.
i cant figure out what theyre tryin to say here. and the data sheets are almost unreadable!
actually they ARE unreadable in certain places.

[triplefour]

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

dont get me wrong, i appreciate even barely readable data sheets rather than NO data sheets

[Amraks]

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

can I have a link to you're voltage regulator?

[mmartell]

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

"U100" is the location of the part on your board. Yours will not be U100. All parts on boards are labelled so as to identify them in their locations. Very helpful when reading a schematic. The regulator is often called an IC.

Pin one is indeed ground, OR is wired to a resistor for a variable regulator. In that case the voltage reading on pin2 (output) should equal the voltage on pin1 + 1.25v. Pin 2 is the output and is usually internally electrically connected to the larger "north" tab. Pin 3 is the input voltage.

Hope that helps instead of confuses, lol.

[triplefour]

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

holy cow u just shined a light on that thanks man so its always 1.25+ whatever the adjustment pin is ? and thats always pin1? pin2 is always output, and pin3 is always input?

[triplefour]

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

ok heres the pics of all the voltage regulators ...and a couple things i thought were voltage regulators for a second but realized they werent but i was wondering if someone could tell me what they are
thanks for the help!

[triplefour]

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

ok so im going to test the L072 G1117's first and from what i can tell from the data sheet they are adjustable...so i should get at least 1.25 plus whatever the adjustment reads... and 5v on the input, right?

[triplefour]

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

ok turns out there were 4 of them on the board.
idunno if i have the u numbers exactly right but i took the closest one

ok

U21
L072 G1117
1. 0.0
2. 1.25
3. 2.5
this one seems good

U19
L072 G1117
1. 1.25
2. 2.5
3. 5.0
good

U17
L072 G1117
1. 2.08
2. 3.31
3. 5.03
2.08+1.25=3.33 which is close enough to 3.31 so this ones good?

U22
L072 G1117
1. 2.05
2. 3.29
3. 5.08
the math checks out here too so far so good.

i also found another voltage regulator i missed in the pictures its at U44 and its a L061 G9117

[triplefour]

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

hmm im having trouble finding this ones datasheet to tell me what voltages to expect. do i have to find the data sheet that says L061 in it or just G9117 by itself is all the same?

[triplefour]

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

hmm so if pin1 has a voltage on it then i know its a variable regulator and i can then just use simple math (+1.25) to see if the output is correct... but if pin1 is 0v and pin2 has some kind of voltage on it besides 1.25 then i would have to look up the datasheet to figure out if that was the correct voltage... correct?

[ivtec]

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

Outstanding you ask the questions and give the answers!

[budm]

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

The Voltage between the ADJ/GND pin and the Output pin should always be 1.25V +/-2%

The inverter circuit is working otherwise you will not have backlights. The screen is showing Blue (instead grayish glow if the T-CON is dead) so the main board is sending some signals but not the correct signals or the T-CON is getting the signals but it has problem.

[mmartell]

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

Not sure how the inverter is faulty if the backlights come on and stay on.

Vizio's are known for bad regulators on the main board and corrupt eeproms (on the main board as well). However I am unsure of the common failure modes for those problems but if you search this forum you should find lots of info that way.

The regulators (or the circuits fed by the regulators) have also been know to be very finicky for whatever reason. In a thread here somewhere I remember the voltage being lower than spec by 0.12v and swapping the regulator fixed the problem.

Good luck.

[ivtec]

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

Not sure how the inverter is faulty if the backlights come on and stay on.

Vizio's are known for bad regulators on the main board and corrupt eeproms (on the main board as well). However I am unsure of the common failure modes for those problems but if you search this forum you should find lots of info that way.

The regulators (or the circuits fed by the regulators) have also been know to be very finicky for whatever reason. In a thread here somewhere I remember the voltage being lower than spec by 0.12v and swapping the regulator fixed the problem.

Good luck.

my Vizio that i repaired had logo, video,sound, and still had to repair the inverters,only after that the tv worked right.

[budm]

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

"my Vizio that i repaired had logo" Do you mean the VIZIO logo that is amber when TV is OFF and White when TV is ON but no backlights? If that is the case, then you did have backlights problem
The OP's TV has backlights, you can see Blue color on the screen, it the backlights are not on, the screen will be black.