Vizio Logo white, no picture/sound and freezes

[Gorrillasnot]

I'm working on a Vizio VW32L HDTV20A.
When plugged in the Vizio logo is amber. I can press the power button and the logo turns white but there is no picture or sound and the TV stays on the white logo and wont turn off with the power button.

After a bit of research it seems that bad voltage regulators are a common issue with this TV.

I think I have narrowed it down to one possibly 2 bad regulators.
The regulator U21 (red arrow in picture) has the following values
U21
Pin1 0.0
Pin2 0.6
Pin3 2.5

and the regulator U16 (circled in the picture)
U16
Pin1 10.6
Pin2 0.0
Pin3 5.0

Shouldn't pin 1 of U16 be around 12v?
I'm a noob when it comes to TV repair. Am I on the right track? Do you think U21 is indeed bad and could it make pin 1 of U16 read low?
Or should I replace both U16 and U21?

U21 has the numbers AMC1117 FO734J


and U16 7805CT RV1707 G


Where would be a good place to order these?

thanks

[Gorrillasnot]

Re: Vizio Logo white, no picture/sound and freezes

bump

[Ltank]

Re: Vizio Logo white, no picture/sound and freezes

U21 does not seem correct. Pin should not be zero. With set off and unplugged use the ohm meter to check for shorts to chassis gnd. There will be a ground pin but two leads should not be shorted to gnd

[Gorrillasnot]

Re: Vizio Logo white, no picture/sound and freezes

sorry for being such a noob but I'm not sure how to test for shorts to ground.

On the ohm setting when I put the probes on pin 1 and 3 I get .16.
I tried that on another similar regulator (U17) and the numbers continually go up.

thanks

[Ltank]

Re: Vizio Logo white, no picture/sound and freezes

I don't have a schematic. Put your meter to read ohms. Place one lead to chassis gnd. Then go to the P.S. connector and check what one has a low resistance to gnd. This would
let you know what voltage is affected.

[Gorrillasnot]

Update: Fixed!

I replaced voltage regulator U21 and the TV so far is working good.

As a desoldering/soldering newbie I have never replaced a surface mount chip before and I didn't have any chip quick but I manged to replace the chip fairly easily. Here's how I did it.

I added a little solder to all the tabs like in this video http://www.youtube.com/watch?v=cNFzBJELFoU , but the chip didn't seem to want to budge.
So I pulled out my spare soldering iron and heated the larger tab with it while at the same time heated the three other tabs with a second soldering iron and the chip came right off.
Next I cleaned up the pads with some deoldering braid, carefully lined up the new chip, added a little solder to the tip of the iron and tacked one of the legs inplace to hold the chip then finished soldering the rest of the legs.

thanks

[Ltank]

Re: Vizio Logo white, no picture/sound and freezes

Good Job! Glad it worked out for you.