Vizio VO42L, Backlite & PS OK, no pic, now what?

[mikew67]

Folks,
Thanks for this useful forum. Previous threads have allowed me to get this far, but now I'm stuck.

Summary:
------------
Vizio model: VO42L FHDTV10A
"Vizio" logo is orange with power off, goes white with power on.
Flourescent backlight comes on, too.
But no video appears, screen is blank/dark, even when pushing Menu and Input buttons on TV.
TV failed suddenly, as if power failed.
Power supply board voltages appear(?) to be OK.
LDO chip output voltages on main PCB appear(?) to be OK.
No apparent bulged caps.

What now? What can I check next?

Details:
---------
Power Board: Peopleworks VE3, PPW-EE42VF-0 Rev. 1.6
LC420WU 6632L-0481A
Main Board: 0171-2272-2605 VO42LF 1018
(connector and IC numbers don't seem to match up with PDF manual for this model found online)

Power Board Voltages:
==============
Connector CN3:
-----------------
Label v-off v-on
24V ~0 23.74v
A ~0 3.356v
B ~0 5.09v
C no connection

Connector CN5:
-----------------
Label v-off v-on
5VSB 5.16v 5.17v
12V ~0 12.23v
POSN 36.0mv 0.2mv
A ~0 3.314V
B ~0 5.05V
C no connection

Main Board LDO Regulator Chip Voltages: (with power on)
====================================
ID Vin Vout Chip label
U15 5.04v 3.207v 1084 0810FL
U16 12.02v 5.01v AZ78057-E1 820D64
U17 5.09v 3.303v K403 G1117
U20 3.26v 1.803v 1084 0810FL ???
U22 5.09v 3.298v K403 G1117
U44 12.08v 9.59v K401 G9117 ???

U15, U17, U20, U22, and U44 appear to be adjustable output regulators and the adjustment leg is approx. 1.25v lower than the output in each case.

So what's next? Are any of these voltages (e.g., U44) fishy? Did I miss an LDO?

TIA,

Mike

[budm]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

So the backlights are on but you just have glowing screen with no pictures or user setup menu that you can see, I would check the fuse on the T-CON board and the voltage on the fuse next.
The LDO voltage between the adjustment leg and the output leg should always be 1.25V (+/-2% or better, depend on the spec of the LDO), Adj Voltage +1.25 = output.

[mikew67]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

T-CON board?
I checked a couple fuses on the main board already (all that I could find -- fairly easy to recognize, white with metal ends. All OK.
Yes, the delta between the adjustment leg and the output is 1.25v on all the LDO's I could find.
Mike

[budm]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

T-CON board is the board sitting under the metal shield in the top middle of the LCD panel assembly. Post the pictures of your TV will help.

[mikew67]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

Aha, one more metal shield to remove. Here's a pic of the T-Con PCB.

Good suggestion. I think we're on the trail of the problem here. The fuse was OK, and the voltage on it (both sides of course) is 12.0v with power on.

But the voltages around U31, the only LDO I could see on the board (just under the rubber stamped numbers) aren't right. The output, pin 2 & tab, is connected to a PCB trace labeled "VCC1.8", but the voltage on it is only 0.569v. (I'm presuming this regulator is supposed to produce +1.8v for the LCD panel bias.) Input (on pin 3) is only 0.837v and pin 1 is 17.2 mv (probably gnd)

Does the 12v through the fuse source U31? Or does it come from another connector pin. So what's upstream from the U31 input that I should check.

Thanks!

Mike

[budm]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

I see two regulated switching power supplies (two round inductors), driven by the IC close to them. Yoy can Ohm out the input pin of the regulator to the fuse to see if it is supply by the 12V input, more likely to be fed by one those two swtiching regulators.
I see pad with VCC label next to L2, I also notice that around L2 has brown area due to heat?
Check the Voltage on the Cathode side of D7 and D8. You may want to get the spec of U5.
U31 does look like 1.8V reg for the processor.
You may also want to check those MLCC (Multi Layer Ceramic Cap) for shorts (they are those brown rectangular shape component).
See shopjimmy.com to see how much this T-CON baord is also.

[selldoor]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

You could also check components labelled FLxx These have been discussed in the past and we seem undecided as to whether they are ferrite beads or fusible links.
Check them as if a fuse.

[kelley]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

Mike,

My Vizio E320VL would go from amber (off) to white (on) vizio logo would appear on screen then it would power off in a few seconds. After reading a bunch of forums I found information on a firmware update issue. I called Vizio and they sent me the items to do a firmware update. TV is now working perfectly. It may not be your issue but contacting Vizio and asking about a firmware update may be worth a try. Good Luck!

[Eadkins]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

I have the same MB with a different problem. The VISIO logo never changes from amber. The PSON signal is not getting to the PS. I cant jump 3V to the PSON on PS and the PS will come alive. any thoughts on where to begin? Ive checked for the obvious bad caps on PS, MB, and inverter. Sorry if this doesnt belong here, as i am new to this forum.

[budm]

Re: Vizio VO42L, Backlite & PS OK, no pic, now what?

Which version of the main board do you have, check the P/N per SJ web site?
http://www.shopjimmy.com/catalogsear...?q=Vizio+VO42L

Then you will start checking the voltage regulators and report the readings per instruction here:
https://www.badcaps.net/forum/showth...999#post300999