Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

Hi Bud,

Please see the picture and compare the value of yours.
The resistor value between G6584 STEPDOWN DC/DC out for core voltage and GND is to low. It's only 18.1 ohm.
Is it yours as well? Sometimes, DC/DC buck output port has very low impedance to GND but it looks to low. Please check with yours. Please.

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

Hi! Bud!

Test results after cutting DIM.

1. PSON, ON/OFF, DIM cutting & LAMP connected.
PSON & ON/OFF 3K pull-up to 5V
http://youtu.be/6IVKPcAbIaA
=> Power & Backlight are on, and stay on.

2. Only DIM cutting & PSON,ON/OFF, & LAMP connected.
PSON by button (signal from main board)
http://youtu.be/OVmsUszjhis
=> symptom is same as first.

What's the role of DIM signal? Now, what's problem on main or power???

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

Lets make it easier, disconnect the cable between the power supply board and the main board, then use 1K resistor between the PS-ON pin and the 5VSTBY pin of the power supply board, then use another 1K between BL-0N and 5VSTBY.
Power up the board to see if the backlights will stay on, if not use another 1K between DIM and 5VSTBY, if the backlights do not stay on then you have problem with power supply/inverter board.

Hi! Bud!

Test results after cutting DIM.

1. PSON, ON/OFF, DIM cutting & LAMP connected.
PSON & ON/OFF 3K pull-up to 5V
http://youtu.be/6IVKPcAbIaA
=> Power & Backlight are on, and stay on.

2. Only DIM cutting & PSON,ON/OFF, & LAMP connected.
PSON by button (signal from main board)
http://youtu.be/OVmsUszjhis
=> symptom is same as first.

What's the role of DIM signal? Now, what's problem on main or power???Hi! Bud!

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

Hi! Bud!

Test results after cutting DIM.

1. PSON, ON/OFF, DIM cutting & LAMP connected.
PSON & ON/OFF 3K pull-up to 5V
http://youtu.be/6IVKPcAbIaA
=> Power & Backlight are on, and stay on.

2. Only DIM cutting & PSON,ON/OFF, & LAMP connected.
PSON by button (signal from main board)
http://youtu.be/OVmsUszjhis
=> symptom is same as first.

What's the role of DIM signal? Now, what's problem on main or power???Hi! Bud!

Some inverter board requires DIM command signal (PWM dimming or Analog Dimming). Your inverter board probably has built-in signal and then main board pulls it LO so the backlights go off.

So on test 1, look at the PS-ON signal on the main board to see if it goes LO.
How about the DCV on the LAMP pin since you it still connected to the main board, does it goes from LO (TV) to HI (TV ON) and stays HI?
BTW, do you get pictures on the screen?

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

Hi Bud,

Please see the picture and compare the value of yours.
The resistor value between G6584 STEPDOWN DC/DC out for core voltage and GND is to low. It's only 18.1 ohm.
Is it yours as well? Sometimes, DC/DC buck output port has very low impedance to GND but it looks to low. Please check with yours. Please.

I do not have the board. What DCV do you get on the out put? You may have to put meter in peak mode to capture the Voltage before the TV goes into shut down.

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

BTW, your dcv report on the 'LAMP' was 3.19V so + about 0.6 for the Diode + Vdrops of the Collector resistor, so the Voltage source for the LAMP cannot be 3.3V, it has to be 5V or so Voltage source feeding that transistor.

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

Some inverter board requires DIM command signal (PWM dimming or Analog Dimming). Your inverter board probably has built-in signal and then main board pulls it LO so the backlights go off.

So on test 1, look at the PS-ON signal on the main board to see if it goes LO.
How about the DCV on the LAMP pin since you it still connected to the main board, does it goes from LO (TV) to HI (TV ON) and stays HI?
BTW, do you get pictures on the screen?

1. You mean, check PSON on main board side even though it is cutted and PSON on power supply side is pulled up?

2. LAMP is Low even it still connected.

3. No. I couldn't get the picture.

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

I do not have the board. What DCV do you get on the out put? You may have to put meter in peak mode to capture the Voltage before the TV goes into shut down.

Peak is same as my first experiment. 1.105V when power on

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

BTW, your dcv report on the 'LAMP' was 3.19V so + about 0.6 for the Diode + Vdrops of the Collector resistor, so the Voltage source for the LAMP cannot be 3.3V, it has to be 5V or so Voltage source feeding that transistor.

I'm sorry but I can't understand your comment.
As I understand, your comment is that LAMP cannot be 3.3V because is driven by source of transistor 5V. Is it right?

But I didn't lie. I show the result in video and just say as what DCV is shown in multimeter. It is 3.19V.

And in previous experiment, after cutting DIM, the symptom is same even though LAMP is low.

Aren't my postings enough information for you to say it is caused by main or power???

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

'But I didn't lie. I show the result in video and just say as what DCV is shown in multimeter. It is 3.19V.' I am not saying anything about lying, I am just tying to explain that to get 3.19V at LAMP, the VCC for the transistor cannot be 3.3V source.
Any way we are already know that the power supply/inverter/backligts are OK. We are just rtying to find what is causing the PS-ON to go low, if you do not want to go any further,, then buy a new main board and see what happen next.

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

'But I didn't lie. I show the result in video and just say as what DCV is shown in multimeter. It is 3.19V.' I am not saying anything about lying, I am just tying to explain that to get 3.19V at LAMP, the VCC for the transistor cannot be 3.3V source.
Any way we are already know that the power supply/inverter/backligts are OK. We are just rtying to find what is causing the PS-ON to go low, if you do not want to go any further,, then buy a new main board and see what happen next.

"But I didn't lie" means that I want to say it comes just from multimeter. Don't get me wrong, please.
I don't want to stop solving problem. I want to know what makes LAMP high or low. I'm an engineer too. I am satisfied everything should be clear.

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

1. You mean, check PSON on main board side even though it is cutted and PSON on power supply side is pulled up?

2. LAMP is Low even it still connected.

3. No. I couldn't get the picture.

The pull up and the switching of the PS-ON, BL-ON HI/LO are on the main board side.
Most of the newer design has pull up on the power supply side so you can do the self test of the power supply board by disconnecting the cable between the main board and the power supply board to see if the backlights will come on and stay on which makes it easier for the tech to narrow down the problem.
Older design you have to use the resistors for forcing on.

https://www.badcaps.net/forum/showpo...&postcount=215

See diagram of the power supply board PS-ON (ON/OFF) receiving pin, the signal is used to Bias on the transistor (QB851) which then turns on the OPTO (PC802S) to supply the Voltage (QB802 linear regulator)to run the rest of the SMPS IC and the PFC IC.

BN44-00259A has built-in pull up resistor.

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

The pull up and the switching of the PS-ON, BL-ON HI/LO are on the main board side.
Most of the newer design has pull up on the power supply side so you can do the self test of the power supply board by disconnecting the cable between the main board and the power supply board to see if the backlights will come on and stay on which makes it easier for the tech to narrow down the problem.
Older design you have to use the resistors for forcing on.

https://www.badcaps.net/forum/showpo...&postcount=215

See diagram of the power supply board PS-ON (ON/OFF) receiving pin, the signal is used to Bias on the transistor (QB851) which then turns on the OPTO (PC802S) to supply the Voltage (QB802 linear regulator)to run the rest of the SMPS IC and the PFC IC.

BN44-00259A has built-in pull up resistor.

Then, this problem can be separated to 100% main board problem?

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

At this point you have backlights but no pictures on the screen, no sound, so yes the main board is suspected.
You can try locate the diagram of the main board to really dig down to be 100% sure it is the main board.
there are more than one version of this TV, the main board is from $80 to $150 RANGE:
http://www.shopjimmy.com/catalogsear...io+E3D420VX%2C

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=>turn off

At this point you have backlights but no pictures on the screen, no sound, so yes the main board is suspected.
You can try locate the diagram of the main board to really dig down to be 100% sure it is the main board.
there are more than one version of this TV, the main board is from $80 to $150 RANGE:
http://www.shopjimmy.com/catalogsear...io+E3D420VX%2C

<Test Result> DCV of PSON on main board when PSON & ON/OFF cutting with 5V pull-up.

before power on: 0V
Power on: 3.3V -> 0V

Power and backlight stay on.

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=&gt;turn off

Something on the main board causes the PS-ON to drop off, what the cause I do not know.
Harware? Firmware?

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=&gt;turn off

Something on the main board causes the PS-ON to drop off, what the cause I do not know.
Harware? Firmware?

That is my question too. You know, I already checked all LDO, STEPDOWN, and PowerMOSFET output and it was good. I think going PSON down to 0V mean there would be short to GND, but after checking, I couldn't find the short point.

I'm worried that if I purchase the new main board, that board would be caused same problem because of external impact......

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=&gt;turn off

<Test Result> DCV of PSON on main board when PSON & ON/OFF cutting with 5V pull-up.

before power on: 0V
Power on: 3.3V -> 0V

Power and backlight stay on.

In post#55 case, (LAMP connected. DIM disconnected)
DIM on main board side = low (but fluctuating)
DIM on power supply side = 3.3V


Post#55 + DIM wire connection (i.e. LAMP connected, DIM connected)
DIM 0V -> 3.3V -> 0V
Power and backlight on and goes off.


In my thought, DIM might be pulled up on 3.3V on power supply.
Without connection, DIM stays on 3.3V and power & backlight stay on as well.

But, after DIM wire connection, DIM goes to low because of main board (I don't know what in main board makes DIM be pulled down to GND).
And power and backlight goes off.

I know something wrong on main board and it makes some signals, such as PSON and DIM, be pulled down to GND to off the power and backlight. However, it's really hard to find the exact reason.

Bud, what do you think about it?

By the way, MERRY CHRISTMAS!!!!!!

[budm]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=&gt;turn off

Looking at you spread sheet I can see all 3 signals (PS-ON, ON/OFF (BL-ON), and DIM all go down to 0, so something must have told the processor to shutdown all the control lines some how. I have seen bad main board that PS-ON drops out but the bl-on and dim still present, or PS-ON stays on but the BL-ON or DIM just drop out.
So I really do not know what your TV is doing at this point. May be you have to look at processor reset line.

[djju]

Re: Vizio TV E3D420VX, No picture, power led on+blink 1time+V logo shown=&gt;turn off

Looking at you spread sheet I can see all 3 signals (PS-ON, ON/OFF (BL-ON), and DIM all go down to 0, so something must have told the processor to shutdown all the control lines some how. I have seen bad main board that PS-ON drops out but the bl-on and dim still present, or PS-ON stays on but the BL-ON or DIM just drop out.
So I really do not know what your TV is doing at this point. May be you have to look at processor reset line.

Yeah, exactly...I wanted to figure out how the reset signal on main board works when power is on, but I couldn't find which part gives the reset on main board. Do you know that? Could you let me know that part gives it?

I really want to check the reset and clock first but I have no oscilloscope in my house, so it is really hard to figure out this.