Vizio E470VL Orange Light Only After F1 Replacement

[tms120]

Thanks ahead of time for your help and consideration.

I am trying to troubleshoot and fix a Vizio E470VL and I am unsure what to do next. I have read numerous threads related to my TV and issue (found one with the exact same issue that the user decided to give up and swap out the data board) with no solution.

I believe my problem began with a power surge that killed the TV (but I also recently noticed that onc of the HDMI ports started to not work before the tv failed) and I was left with a TV with no power light. I checked the fuses and I replaced F1 on the main board. The power light is now working, but I get no response from the power button or remote. I examined both boards and did not see anything out the the ordinary in terms of damage or bulging caps.

I currently have the following voltages:

The harness going from the power board to the main board:

DIM.............0.694v
LAMP............0v
I-ON/OFF......0v
PS_ON.........1.14v Steady, get a quick 3.096 at first measurement
12V..............12.19v
12V..............12.18v
12V..............12.19v
SGND...........0v
SGND...........0v
SGND...........0v
SGND...........0v
5V................5.06v
5V................5.06v
5V................5.07v


U8 (7805LT)........12.14v, 0v, 4.96v

U2 (1117)...........2.02v, 3.264v, 4.92v

U7 (1117)...........2.007v, 3.236v, 4.82v

U4 (1117)...........0v, .323v, .527v (Others stated this s/b 0, 1.25, 3.3)

U3 (G1084).........0.315v, .518v, 4.83v (Feeds U4, low adjusting V)

U46 (1117).........1.986v, 3.22v, 4.84v

U33 (4953GM)
0 -------11.93 (Gates are not switching)
0--------12.16
0--------11.93
0--------12.16

What additional information can I provide?

[jetadm123]

Re: Vizio E470VL Orange Light Only After F1 Replacement

Appears something is wrong with U3. There's no voltage output, which is why you see nothing at U4. I believe U3 is an adjustable voltage reg, where the output is controlled by two external resistors. Check the value of these resistors. Also, there could be a short at the output of U3. You can test for this by setting your meter to a low ohms setting and measuring between the output pin of U3 and ground. If it measures a short, you'll have to perform the same test with U3 removed and measure between the output pad and ground. If the short is gone, then replace the regulator.