VIZIO VX37L No picture or sound.

**marlboroa** · 11-10-2012, 09:02 PM

Re: VIZIO VX37L No picture or sound.

I did test the power supply and i have all the voltages except for A and B they read 0

**budm** · 11-10-2012, 09:46 PM

Re: VIZIO VX37L No picture or sound.

If you are reading 0V at A and B, A and B are the control signals generated by the main board to turn on the backlights and Dimming control. Are you getting PS_ON >3VDC?
Can we see good clear pictures of the boards? Is this the same as your TV?
http://s807.photobucket.com/albums/y...37L%20HDTV10A/
You voltage reading of the regulators are a little confuse.
If you look at the regulator 1117 series with the big tab up
Fixed output regulator:
Left pin (1) will be Ground
Center pin or Tab (2) will be output pin
Right pin (3) will be the input pin

Adjustable output regulator (it will need two resistors, one is between Ground and Adj pin, another one is between Adj pin and Output pin):
Left pin (1) will be the Adust pin.
Center pin or Tab (2) will be output pin
Right pin (3) will be the input pin

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.
So can you label the pins and the voltage you are reading on those regulators?
AMC117
f0722f

U7 P/N?
3.21
1.11 This one does not look right
0.02

U33 P/N?
5.09
3.22 This one should be 3.3
1.98

U8 P/N
5.11
3.25 looks OK (1.25 +2.01 = 3.26)
2.01

U2 P/N?
5.09
3.26 looks OK (1.25 + 2.02 = 3.27)
2.02

U4 P/N?
5.09
3.28 looks OK (1.25 + 2.04 = 3.29)
2.04

K117515
730

U9
3.21
1.49 looks OK, it looks like 1.5V regulator.
0.00

**marlboroa** · 11-11-2012, 10:46 AM

Re: VIZIO VX37L No picture or sound.

The picture of the main board in your link is just like mine. same part number and all. I took the readings clockwise. so since the big tab is to the left i guess the way i listed them would be
3
2
1
I do have a PS_On reading of 3.07 which seems a tad low.
The part numbers for the U regulators are all AMC117 f0722f except for U9. its a
K117515 730

**marlboroa** · 11-12-2012, 09:03 AM

Re: VIZIO VX37L No picture or sound.

how can i get the U33 up to 3.3 volts?

**tom66** · 11-12-2012, 09:05 AM

Re: VIZIO VX37L No picture or sound.

You should re-test U33. If it still shows low 3.22V, it could be faulty and should be replaced. However, U7 looks worse, as budm pointed out.

**marlboroa** · 11-12-2012, 09:40 AM

Re: VIZIO VX37L No picture or sound.

I retested it and its 3.22 still. I know theses are all adjustable regulators but i dont think i have any laying around. I do have a few A1-AS1117L but cant find a data sheet to see if they will work.

**tom66** · 11-12-2012, 10:34 AM

Re: VIZIO VX37L No picture or sound.

If they do not have -33 after them or similar they may be adjustable but why take the risk? You could burn the main board due to over voltage. Digikey has voltage regulators for cheap:

http://www.digikey.com/product-detai...4-1-ND/1217057

**MisterD** · 11-12-2012, 11:01 AM

Re: VIZIO VX37L No picture or sound.

I replaced U7 and U33 both on a 42" Vizio, had low output voltage on U7 and U33 has a high failure rate.. both were same part#, I bought them from Digikey and even got extras since they were so cheap. After replacing them the TV now powers on and works fine.

**budm** · 11-12-2012, 11:05 AM

**tom66** · 11-12-2012, 11:21 AM

Re: VIZIO VX37L No picture or sound.

And shipping is under $3 in continental US, I believe.

**Trackstar23** · 11-13-2012, 10:38 AM

Re: VIZIO VX37L No picture or sound.

Originally posted by MisterD

I replaced U7 and U33 both on a 42" Vizio, had low output voltage on U7 and U33 has a high failure rate.. both were same part#, I bought them from Digikey and even got extras since they were so cheap. After replacing them the TV now powers on and works fine.

Had the same happen with another 42 inch vizio (vw42l) and ended up doing the same thing after it still had issues after replacing u33. Been working 3 months now.

**marlboroa** · 11-22-2012, 02:04 PM

Re: VIZIO VX37L No picture or sound.

Fixed. Replaced U33 and U7

VIZIO VX37L No picture or sound.

VIZIO VX37L No picture or sound.

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