Vizio VU42L FHDTV10A orange light, but won't turn on

[Daveleone]

Hi there! I'm a hobbyist newb who is really excited and interested in learning how to actually REPAIR these boards (rather than just replacing the defective board as I have done in the past). This forum looks like an incredible resource and I'm looking forward to your help!

I have a non-working Vizio VU42L FHDTV10A that an acquaintance gave me. When plugged in the Vizio logo illuminates orange, but the TV does not turn on when you press the power button (logo does not turn white). Attached are pictures of the back of the TV, the power supply, and the main board. I took 2 sets of close-up pics of the main board because the first one had flash glare (though the rest of the PCB was easy to read), so I took another set without the flash. Hopefully you can get what you need. If not, let me know and I will take more photos. After reading a lot of posts in this forum regarding similar TVs, I believe the problem is in the main board, so I've tested the voltages coming off of the power supply and all of the voltage regulators on the main board. Here are the results:

POWER SUPPLY
--------------
CN2 (to Slave Inverter)
24V pins = 0v
SGND pins = 0v
A = not connected
B = not connected
C = not connected

CN3 (to Master Inverter)
24v pins = 0v
SGND pins = 0v
A = 0.20v (and drains as I measure it)
B = 0.01v
C = not connected

CN5 (to Main Board)
PS_ON = 0.02v
12v pins = 0v
SGND pins = 0v
5VSB pins = 5.22v
A = 0.23v (and drains as I measure it)
B = 0.01v
C = not connected

MAIN BOARD
------------
FUSES
------
F2 (horizontally oriented fuse in the picture)
left side = 5.21v
right side = 5.19v

F1 (vertically oriented fuse in the picture)
bottom = 0v
top = 0v

REGULATORS
------------
U3
AZ7085T
E1 652500
pin 1 = 0v
pin 2 = 0v
pin 3 = 0v

Q27 (this doesn't have a U number, at least not on the front of the board - this is the one on the right side of the board just below the left side of the P/N barcode label)
C5886
pin 1 = 0v
pin 2 = 0v
pin 3 = 0v

U2
AMC1117
F0713J
pin 1 = 2.05v
pin 2 = 3.30v (tab matches)
pin 3 = 5.17v

U8
AMC1117
F0713J
pin 1 = 2.07v
pin 2 = 3.33v (tab matches)
pin 3 = 5.19v

U33
AMC1117
F0713J
pin 1 = 2.06v
pin 2 = 3.31v (tab matches)
pin 3 = 5.17v

U9
K1117
515715
pin 1 = 0v
pin 2 = 1.52v (tab matches)
pin 3 = 3.31v

U7
AMC1117
F0713J
pin 1 = 0.08v
pin 2 = 1.28v (tab matches)
pin 3 = 3.31v

U10
AC 1084 0712FL
pin 1 = 1.39v
pin 2 = 2.66v (tab matches)
pin 3 = 5.15v

Let me know if there's anything else you need!
Thanks so much!
--Dave

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Bump

[dick_barton]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

The 12V is missing from the power supply board. Can you disconnect the power supply connections from the main board and connect the 5vSTB to PS_ON using a 1K resistor and then check you have the 12V supply.

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

The regulators outputs are OK. U3 is ZERO because there is no switched 12V feeding it. Right now the PS_ON = 0.02v so there will be no switched 12V/24V.
Can you check the DCV on the control panel switches (Vizio 3642-0042-0156 (0174-1770-1844) Keyboard Controller) to see if there are any actions?http://www.shopjimmy.com/catalogsear...VU42L+FHDTV10A

Also try disconnecting the IR board (Vizio 3642-0022-0189 (0171-1671-0501) IR Sensor.

http://www.shopjimmy.com/catalogsear...VU42L+FHDTV10A

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

The 12V is missing from the power supply board. Can you disconnect the power supply connections from the main board and connect the 5vSTB to PS_ON using a 1K resistor and then check you have the 12V supply.

Thanks for the reply!

I didn't have a 1k resistor handy, but I also have a working GV42L TV (same power supply, different rest of the parts) and I was able to do 2 tests.

1) I took the power supply from the VU42L in question and put it in the GV42L. The GV42L powered right up.
2) I took the power supply from the GV42L and put it in the VU42L. The VU42L would not power on (same results for both power supplies).

So that leads me to believe the power supply is ok.

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Can you check the DCV on the control panel switches (Vizio 3642-0042-0156 (0174-1770-1844) Keyboard Controller) to see if there are any actions?

Thanks for the reply! Here's what I found.

I disconnected the IR sensor from the control panel switch board and did the testing. With the the TV in standby (orange light) I tested the voltages of the signals on the connector at the top of the control panel switch board, without pressing the power button.

(from left to right in the attached picture)
KEY33 = 3.33v
ADIN-0 = 0v
ADIN-1 = 0v
GND = 0v
GND = 0v
IR = 3.26v
5VSB = 5.20v
5VSB = 5.20v
WHITE = 2.88v
AMBER = 3.36v

I also tested the terminals at the power button itself, without the button pressed.
(orientation from the front of the board as in the picture)
Top Left = 2.37v
Bottom Left = 2.37v
Top Right = 0v
Bottom Right = 0v

When I pressed the power button I noted the following changes:
ADIN-0 = 0.02v
ADIN-1 = 2.37v
Top Right = 2.37v
Bottom Right = 2.37v
...the rest of the readings were the same as the unpressed button readings.

The TV still did not power on. What next?

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Nothing out of ordinary. Yep, you do have main board problem since we already know that it is not sending the PS-ON to turn on the power supply.
Try disconnecting the cable between the main board and the T-con to see if the TV will start up.

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Try disconnecting the cable between the main board and the T-con to see if the TV will start up.

When I unplugged the cable from the main board that goes to the T-con (the multi-colored one directly above U7), and turned on the power strip, waited 5 minutes, pressed the power button, and no joy. The TV still did not power on. HOWEVER, interestingly, I then turned the power strip back off, plugged the T-con cable back into the main board and turned the power strip back on and immediately heard a relay click. Then I pressed the power button and the TV turned on. The TV worked for about 20 minutes, while I had it on Antenna input watching off-air digital TV, then the picture froze and sound stopped and I could not power OFF the TV with the power button or the remote. I unplugged the power, and plugged it back in, and I'm back to the original "orange light, no power on" problem.

?? ideas ??

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Bad solder joints? Also try tightened all the boards mounting screws, and reseat the cables.
Also try heating the main board for 2~3 minutes then plug the TV into the outlet to see what happen.

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Will do. Heat with what, a hair dryer? Or heat gun? And heat the whole board?

Also, I noticed that the one time the tv worked I heard the relay click immediately after I plugged it in (before I pressed any button). When it's not working I hear no relay click when I plug it in. Does that information help at all?

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Hair dryer.

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

No luck. I tried heating the main board and no change. So I tried heating each of the other boards (ps, t-con, master inverter, slave inverter) one by one just in case. No change.

Then I unplugged all of the cables, unscrewed the main board, picked it up, re-seated it and screwed it back down. Still no change.

I cannot reproduce the "power on" event. Maybe it was a fluke that whatever the faulty component is happened to work temporarily that one time I turned the tv on l, and wasn't really related to unplugging and replugging the t-con cable. ?

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

I do not believe this TV uses Error signal from the T-CON board to shutdown the main board from coming on (not 100% sure), so the TV should be able to be turned on without the T-CON board connected.
I have no other suggestion on what else you can do. I am leaning toward bad main board.

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Ok, I was hoping to try to fix this main board. But do you think it's not worth delving deeper into the problem and I should just replace the board in this case?

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Unless we can find the correct diagram for the board and have a scope handy.

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

ok, I bought a replacement main board off of eBay. Will let you know the results when it arrives. Thanks for all the help!

[Daveleone]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

I got the replacement board already. Plugged it in and the tv is working perfectly.
Someone had Private Messaged me that I should try replacing the eeprom on the main board (just below the cpu). But, I figured for $35 I might as well just get the new board. Maybe next time.

Thanks for all the diagnostic help!

[budm]

Re: Vizio VU42L FHDTV10A orange light, but won't turn on

Thanks for the follow-up.