Vizio E321VL LCD - has backlight, but no video

[SurrealMustard]

I'm working on a Vizio E321VL LCD television that powers on and off okay and lights the backlight, but doesn't put anything on the screen. Could this be a T Con issue? If so, I'm having trouble locating the T Con board on this unit and was wondering if anyone could help point me in the right direction.

[budm]

Re: Vizio E321VL LCD - has backlight, but no video

It has integarted T-CON into the LCD panel assembly.
You can try and see if you do have 12Vdc at least at one of the pin of the connector that goes to the LCD panel when TV is tured on.

[SurrealMustard]

Pins

It has integarted T-CON into the LCD panel assembly.
You can try and see if you do have 12Vdc at least at one of the pin of the connector that goes to the LCD panel when TV is tured on.

How do I know which pin to test?

[budm]

Re: Vizio E321VL LCD - has backlight, but no video

You may have EEPROM problem.
http://www.shopjimmy.com/vizio-3632-...repair-kit.htm

Verify your board P/N.
From SHOPJIMMY:
Part 1

Symptoms:
- TV turns on when you press the power button but has no backlight.
Description Quantity Board Location
Integrated Circuits 1 U21

Part 2

Symptoms:
- TV turns on when you press the power button AND has backlight, but there is no image/picture
- Display is stuck/frozen on the welcome screen
- TV won't power on with remote/buttons
- TV turns on when you press the power button when first plugged-in, but it won't turn back on after 30 minutes of being off
- TV shuts off and goes back to standby mode
Description Quantity Board Location
Integrated Circuits 1 U18

[ecking767]

Re: Vizio E321VL LCD - has backlight, but no video

I'm working on a Vizio E321VL LCD television that powers on and off okay and lights the backlight, but doesn't put anything on the screen. Could this be a T Con issue? If so, I'm having trouble locating the T Con board on this unit and was wondering if anyone could help point me in the right direction.

Check U21 its a MOSFET pin 5 to 8 is all connected, I believe is feed the T-CON circuit.

do you get any sound?

if your TV is turning off and on it may not be eeprom related.

[SurrealMustard]

differential diagnosis

if your TV is turning off and on it may not be eeprom related.

I'm sorry, I should have been more specific. I meant to say that the set responds normally to the power button.

Check U21 is a MOSFET pin 5 to 8 is all connected, I believe is feed the T-CON circuit.

How would I go about checking those pins?

do you get any sound?

I'm not entirely sure what input it's on, so I don't know for sure. If it would help, I could try to contact the set's owner to see if he remembers if the sound works or not.

You may have EEPROM problem.
http://www.shopjimmy.com/vizio-3632-...repair-kit.htm

Verify your board P/N.
From SHOPJIMMY:
Part 1

Symptoms:
- TV turns on when you press the power button but has no backlight.
Description Quantity Board Location
Integrated Circuits 1 U21

Part 2

Symptoms:
- TV turns on when you press the power button AND has backlight, but there is no image/picture
- Display is stuck/frozen on the welcome screen
- TV won't power on with remote/buttons
- TV turns on when you press the power button when first plugged-in, but it won't turn back on after 30 minutes of being off
- TV shuts off and goes back to standby mode
Description Quantity Board Location
Integrated Circuits 1 U18

Interesting. I will keep that in mind; thank you for sharing.

[ecking767]

Re: Vizio E321VL LCD - has backlight, but no video

So it doesn't power off by pressing the power button?

you need a multimeter to check voltages on that MOSFET

To check for sound ,connect something to one of the HDMI PORT and power on TV, wait about 20 second to allow the TV to pick up any signal, turn up the volume. then do the following:

using your remote you can scroll through the inputs:

press "input" then the down arrow, then enter. wait about 5 to 10 seconds.

do this about 5 time (5 INPUTS)

[SurrealMustard]

troubleshooting

So it doesn't power off by pressing the power button?

No. It powers on when I press power and turns off when when I press power.

you need a multimeter to check voltages on that MOSFET

Just checking the pins to ground or against each other?

To check for sound ,connect something to one of the HDMI PORT and power on TV, wait about 20 second to allow the TV to pick up any signal, turn up the volume. then do the following:

using your remote you can scroll through the inputs:

press "input" then the down arrow, then enter. wait about 5 to 10 seconds.

do this about 5 time (5 INPUTS)

If the remote is not available, can the button on the side be used the same way instead? Would channel up/down be used in place of the arrow keys?

[ecking767]

Re: Vizio E321VL LCD - has backlight, but no video

if the TV is powering ON and OFF then trying to get sound will help a lot in troubleshooting

No remote then press the input button twice and then wait 10 sec.

red probe on any pin 5 to 8 of the MOSFET and black probe to ground

[SurrealMustard]

Results

if the TV is powering ON and OFF then trying to get sound will help a lot in troubleshooting

No remote then press the input button twice and then wait 10 sec.

red probe on any pin 5 to 8 of the MOSFET and black probe to ground

All right, now we're getting somewhere. Using that technique, I was able to confirm that sound is indeed working. After testing, the MOSFET at U21 is showing no voltage on pins 5 through 8. Does this mean the component is bad and that I should get the replacement unit from ShopJimmy?

[budm]

Re: Vizio E321VL LCD - has backlight, but no video

It may mean that the MOSFET is not getting the signal from the processor to turn it on, or there is no Voltage on the input side of the MOSFET.

[SurrealMustard]

diagnosis confirmation

It may mean that the MOSFET is not getting the signal from the processor to turn it on, or there is no Voltage on the input side of the MOSFET.

Does that mean I'm looking at a bad mainboard then?

[budm]

Re: Vizio E321VL LCD - has backlight, but no video

You can try to verify the MOSFET further but you need to get the spec sheet to get the pin out and see which pin is the Gate, which pin is the Drain, and which pin is the Source.
At this point you do have problem with the main board.

[SurrealMustard]

Win!

You can try to verify the MOSFET further but you need to get the spec sheet to get the pin out and see which pin is the Gate, which pin is the Drain, and which pin is the Source.
At this point you do have problem with the main board.

Good call, mainboard was the culprit.