vizio v037l fhdtv20a no picture

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

Not on the main board just on the PSU.

[tom66]

Re: vizio v037l fhdtv20a no picture

Are all the fuses on the PSU OK then?

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

Not on the main board.

[tom66]

Re: vizio v037l fhdtv20a no picture

Sorry, I'm lost. Are there any fuses on the PSU (apart from the 8mm x 20mm mains ones.)

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

Not that I can find

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

The big capacitor rated 648 I'm only getting 604 uf.

[tom66]

Re: vizio v037l fhdtv20a no picture

Which capacitor is rated 648? That is a very unusual rating.

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

Actually its rated 680. The one on the right under the cover.

[budm]

Re: vizio v037l fhdtv20a no picture

The problem seems to be in your main board from the reading of the LDO outputs and also bad PS_ON signal by the main board.
Can we see the pictures of the whole main board?

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

The 1st pic I uploaded is the whole board minus 3 caps.

[budm]

Re: vizio v037l fhdtv20a no picture

As log as there are no LDO regulator to the right of the pciture.

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

Here's the right side.

[budm]

Re: vizio v037l fhdtv20a no picture

u21
l112
g1117
1. .6
2. 1.240 (The output should be = 1.25 +0.6 = 1.85V)
3. 2.514

u19
l112
g1117
1. 1.12
2. 2.515 (The output should be = 1.25 +1.12 = 2.37V)
3. 5.02

This is the way to figure out if the adjustable regulator is good or not:
Notes: we are looking at the regulator with the Big tab up (the big tab is tied internally to the center pin).
Adjustable regulator will have two resistors attached to it, one resistor (Rfb) is between pin1 and pin2, another resistor (Rg) is between pin1 and ground. Pin3 is an input pin.
The voltage between the Adjust pin (left pin) and the center pin (Pin2, output) will always be 1.25V +/- 2% (this is the precision voltage reference), if it is not, it is bad.
To figure out what the output voltage should be: measure the voltage between pin 1 and ground and add 1.25V to that number, that is the output voltage on pin 2 but you have to make sure you do have 1.25 between pin 1 and 2 as noted above

[tom66]

Re: vizio v037l fhdtv20a no picture

Good catch on U21. I completely missed that.
Not sure about U19 though. It would be rare for an LDO to fail with increasing output. But I suppose anything's possible with the cheap LDOs vizio used.

[budm]

Re: vizio v037l fhdtv20a no picture

I have MAC Cinema Display monitor with 3.3V that puts out 4V, it can be due to leaky pass transistor inside. Anything possible.

[tom66]

Re: vizio v037l fhdtv20a no picture

I have also had temperature sensitive LDOs. Freeze-spray them and they come right back to life for a few minutes.

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

I am very new at this and I am trying to understand what is going on. I tested all of the regulators vdc between 1 and 2 pins and I get 1.25 on all but u44 and u16. I soldered a fuse on top of f3 and jumped the 5dcv to pson and the screen is on.

[tom66]

Re: vizio v037l fhdtv20a no picture

Screen lit up? Or did you get an actual picture?

[beer-b-q]

Re: vizio v037l fhdtv20a no picture

Just screen. Should I in cable and see what happens?

[tom66]

Re: vizio v037l fhdtv20a no picture

I think the regulators Budm pointed out need replacing, but it confirms the power supply is working properly.
You will likely not get video (no menus or cable, HDMI, etc.) until the regulators are replaced.