Vizio E3D320VX sound but no picture

[Techbill]

I can temporarily short backlight on line to ground and backlight will come on and work normally, until shut off and back on again, than back to same problem. All psu voltages are normal. Seems the backlight is not receiving the on signal from the processor. Components between processor and back light IC test ok. Any help would be appreciated.

[budm]

Re: Vizio E3D320VX sound but no picture

Pictures of the boards and the backside of the TV? The BL_ON signal line should change state when TV is toggle on and off, if not, the main board will be the next step to test, start at the voltage regulators.

[Techbill]

Re: Vizio E3D320VX sound but no picture

BL_on signal has no voltage with TV off, goes to 3.2 volts, when backlight comes on at startup, quickly goes low, down to 2 volts but immediately back up to 3.2 volts. I forgot to mention, the back light comes on at initial power up, shows logo, than goes off. Stays off unless I ground BL_on to ground, than will stay on most of the time, some times I have to ground it out a couple of times for it to stay on. Will work on pics.

[budm]

Re: Vizio E3D320VX sound but no picture

"BL_on signal has no voltage with TV off, goes to 3.2 volts,when backlight comes on at startup" So it is active high logic, 3.2V = ON, <.6V = OFF which is typical for most TV.

But then this does not make sense:
"Stays off unless I ground BL_on to ground, than will stay on most of the time"

[Techbill]

Re: Vizio E3D320VX sound but no picture

Pics of the boards

[Techbill]

Re: Vizio E3D320VX sound but no picture

"Stays off unless I ground BL_on to ground, than will stay on most of the time"
I meant the back light stays on, once I ground BL_on line.

[Techbill]

Re: Vizio E3D320VX sound but no picture

Circled a regulator that may be bad, got no voltage on top leg as viewed, 3.7 volts on center leg, 0.6 volts on bottom leg.

[Techbill]

Re: Vizio E3D320VX sound but no picture

Budm, can u possibly id that regulator for me?

[Techbill]

Re: Vizio E3D320VX sound but no picture

One more piece of info. I ordered a new main board, board I got I think is defective cause with it installed, tv comes on, same as before, but after showing logo, whole tv shuts down. Power light goes off, this doesn't happen with original board, just loses back light.

[dhack61]

Re: Vizio E3D320VX sound but no picture

Has anybody come up with a solution. Same problem on same set.

[dhack61]

Re: Vizio E3D320VX sound but no picture

For Whats its worth. Found a bad solder spot on one of the VR's got backlight to come on but no picture. Cleaned and reseated ribbon cables and set has been working /on for 24hrs.

[JTDawg1202]

Re: Vizio E3D320VX sound but no picture

Hey. I have the same problem as above only the tv comes on with logo for about 3 seconds, back light goes off, comes on again with a blank screen after a few seconds, then shuts off again after 3 seconds with power still remaining on with audio working and picture visible with a bright flash light against the screen. I'm trying to isolate the problem down to which component (or board if needed) needs to be replaced. When the back light comes on for 3 seconds, a blue led on the power board is visible up till the point the bulbs shut off. What does it mean? Also, when i first took the tv apart, i layed the tv with bulbs exposed up, turned on the tv, and the bulbs came on and remained that way until i shut the set off. There doesn't seem to bee any blown capacitors or flickering/ discolored bulbs so i don't know what to try next. I read this thread with the VR info but i don't know how to identify or tell what voltage i should be getting out of each regulator. I'm kinda lost so any additional help on this issue would be greatly appreciated!

[JTDawg1202]

Re: Vizio E3D320VX sound but no picture

The BL_ON also will change when backlight turns on and off.

[budm]

Re: Vizio E3D320VX sound but no picture

The BL_ON is generated by the main board, so if the main board stops sending the BL_ON signal to turn on the backlights then the backlights will shutdown, you need to find out why the BL_ON goes LO. When TV is on, the BL_ON should remain HI until you turn off the TV or when the TV goes into standby mode.

[JTDawg1202]

Re: Vizio E3D320VX sound but no picture

The BL_ON now stays hi at 3.26v and goes down to 3.2 when bulbs come on. It seems to be staying HI until TV is shut off unless the slight change makes a bit of difference.

[JTDawg1202]

Re: Vizio E3D320VX sound but no picture

When I took the power board out, i noticed after plugging it back in the back lights will now only come on for half a second each time the tv is powered up.

[budm]

Re: Vizio E3D320VX sound but no picture

The BL_ON now stays hi at 3.26v and goes down to 3.2 when bulbs come on. It seems to be staying HI until TV is shut off unless the slight change makes a bit of difference.

That is fine as long as the BL_ON (typical >2V = ON, <1V = OFF, you can look at the spec of the LCD panel to see the exact numbers) is staying high and applied to the inverter board, along with 24VDC to power the inverter then the backlights should stay on, if not, then you have inverter or lamps problem.
How about the pictures of your boards?

[JTDawg1202]

Re: Vizio E3D320VX sound but no picture

Here are pics of boards:

[JTDawg1202]

Re: Vizio E3D320VX sound but no picture

Where would I check for the 24v dc?

[budm]

Re: Vizio E3D320VX sound but no picture

OK, now I se your power supply/inverter board combo, this one the inverter dose not use 24VDC for powering the inverter circuits, it uses about 360~400VDC for driving the two inverter transformer.
So let me get this correctly, the backlights flashes on for second then black out, but the BL_ON is still present when the backlights go out?
Can I also get the straight shot picture of the whole board?