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

[budm]

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

Sorry, It is pin on, it was late last night tracing the board from the pictures.

[djju]

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

I looked at the pin 13 'LAMP' connection on the power supply board, it is connected to the Anode of D714, the Cathode is connected to resistor, another end of the resistor is connected to the IC??? PIN 3??? (or pin 7???).
So that means the pull-up resistor is on the main board and the Voltage is then sinked through D714 through the resistor and the IC pin when that pin of the IC is switched to GND.
At this point I will wait to see the result of the suggestion I made.
BTW, you are seeing 0.1V on the LAMP pinon the power supply board, but if the Cathode is HIGH then the Diode will be reverse bias so you may not see anything on the Anode side.

Okay, you mean, LAMP is pulled up inside of main board and something wrong in LAMP on power board, then it will be reverse bias to cut to connect to GND and it can be input 3V indicator to main board and main board will cut the power...right?

BTW, what does mean the "pinon"?? "LAMP pinon"???

[budm]

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

I looked at the pin 13 'LAMP' connection on the power supply board, it is connected to the Anode of D714, the Cathode is connected to resistor, another end of the resistor is connected to the IC??? PIN 3??? (or pin 7???).
So that means the pull-up resistor is on the main board and the Voltage is then sinked through D714 through the resistor and the IC pin when that pin of the IC is switched to GND.
At this point I will wait to see the result of the suggestion I made.
BTW, you are seeing 0.1V on the LAMP pinon the power supply board, but if the Cathode is HIGH then the Diode will be reverse bias so you may not see anything on the Anode side.

[budm]

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

So you can force on the power supply and the Inverter board on and the backlights stay on as long as the force on resistors are connected, so that means there is no problem with the inverter circuit.
Then we can try this, leave those two resistors in place, and also remove those two wires (PS-ON and BL-ON) that go back to the main board so we do not back feed these force on signals back to the main board and see if the TV will stay on, at the same time monitor the 'LAMP' signal.

[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. This is test video link. https://youtu.be/mFN6-j_NkK4

PSON - 3Kohm - 5V STBY
ON/OFF - 3Kohm - 5V STBY

the backlights stays on and LAMP is 1.1mV

What does it mean? Power supply is OK? LAMP active low is No problem?

At this point, I have another question.
Without cable connection and PSON and ON/OFF are turned on forcibly, LAMP is active low forcibly even though power supply board has problem.
You said LAMP is indicator to let main board know there is something wrong.

But PSON & ON/OFF are on by power supply itself, without mainboard.
And backlight stays on and LAMP is low.
Then, CN201 result, LAMP 3V -> 0V is caused by mainboard? LAMP signal voltage changing is caused by mainboard? Is LAMP input signal to main board, isn't it?

I'm sorry Bud, but I'm really confuesd.

[budm]

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

BTW, the cold side of the power supply-inverter only has 5V and 12V, so there is no pull-up toward 3.3V supply, only 5V power source since there is no 3.3V on the power supply board. So the LAMP signal error may be due to lamps or Inverter problem but we need to find out first if it is active HIGH (HIGH = ERROR) or active lo, more likely it is active LOW (LOW = ERROR).

[budm]

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.

[djju]

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

In put to the main board,
Just only connection from 5V----1K----LAMP is the 5V pull-up. (even though its current is very small). That is correct, you must remove the lamp wire that goes to the power supply board first then use the resistor between that end of the wire and 5V. We are feeding the main board.
Or you can use 3V battery if you want.
Or you can try without having the wire connected to anything, it may have pull-up resistor on the main board already, you can verify that by keeping the meter on that wire you remove.

Thank you, Bud. You mean,

1. Cut wire between (main)LAMP------:scissor:-------(power)LAMP
2. Test 1.
(Because (main)LAMP may be 3V pulled up), 3V-----??ohm----(main)LAMP inside main board
3. Test2.
Wire (main)LAMP-----(+(1.5V+1.5V battery)-)------(main)GND
4. Test3.
Wire (main)LAMP-----------1117 3.3V STBY out

Is it correct?

However, I can't still understand your feedback that you must remove the lamp wire that goes to the power supply board first then use the resistor between that end of the wire and 5V. We are feeding the main board.. It is still 5V pull up. It could cause voltage compatibility problem.

[djju]

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

BTW, we still need to see the whole back side of the board so we can see how all the boards are connected together.

Hi Bud

This picture is back side of tv. Nothing wrong of connection.

[budm]

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

In put to the main board,
Just only connection from 5V----1K----LAMP is the 5V pull-up. (even though its current is very small). That is correct, you must remove the lamp wire that goes to the power supply board first then use the resistor between that end of the wire and 5V. We are feeding the main board.
Or you can use 3V battery if you want.
Or you can try without having the wire connected to anything, it may have pull-up resistor on the main board already, you can verify that by keeping the meter on that wire you remove.

[djju]

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

That is why you have to use 1K resistor, never hook up directly without the resistor. 1K will limit the current to only 5mA.

Hi Bud, Thank for your kind feedback.

My question is not current, but voltage.
You mean, LAMP might be an input signal to the main board. Is it right?
Then, the logic input level of main board should be 3V because when the backlight is on for a while, its level is 3.19V. After that, it goes to GND after backlight off and power led blinking 1 time.
As I understand, you said, LAMP signal changing should tell to the main board there is something wrong.
Then, LAMP should be input to the mainboard and we have to keep signal compatibility (3.3V, not 5V)
Just only connection from 5V----1K----LAMP is the 5V pull-up. (even though its current is very small)

Is it input to the main board or the power supply?

[budm]

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

That is why you have to use 1K resistor, never hook up directly without the resistor. 1K will limit the current to only 5mA.

[djju]

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

Thanks Bud,
You mean, lamp signal is the indicator that let the main baord know something wrong on the power supply board?
probably, power supply might have the problem and it makes main board cut the power? Power supply board may have to be changed?

Is it okay that 5v to LAMP instead of 3.3v? Is Logic voltage level okay?

[budm]

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

BTW, we still need to see the whole back side of the board so we can see how all the boards are connected together.

[budm]

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

So sorry, i forget that you have power supply inverter combo board, so you need to do the experiment on that 'LAMP pin.

[djju]

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

The over load protection circuits are on the power supply board, the power supply board may send the error signal to the main board telling there is problem then the main board goes into shutdown.
One pin I do not really know what it is really for is pin 13 'LAMP' I do not know if it should stay HIGH >2V for normal, or HIGH = abnormal, or LOW (<1V) = Normal or not normal.
You can pull just pull that wire that goes to the power supply board and connect that wire to GND so the main board will see LOW signal feeding it, see what happen when you turn on the TV. If it does not change then you can pull that wire HIGH using 1K resistor between that wire and the STBY 5V and see what happen.

Thanks Bud,
You mean, lamp signal is the indicator that let the main baord know something wrong on the power supply board?
probably, power supply might have the problem and it makes main board cut the power? Power supply board may have to be changed?

[budm]

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

The over load protection circuits are on the power supply board, the power supply board may send the error signal to the main board telling there is problem then the main board goes into shutdown.
One pin I do not really know what it is really for is pin 13 'LAMP' I do not know if it should stay HIGH >2V for normal, or HIGH = abnormal, or LOW (<1V) = Normal or not normal.
You can pull just pull that wire that goes to the power supply board and connect that wire to GND so the main board will see LOW signal feeding it, see what happen when you turn on the TV. If it does not change then you can pull that wire HIGH using 1K resistor between that wire and the STBY 5V and see what happen.

[djju]

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

Hi Bud,

Do you kmow which part is PMIC on the main board?

Or, do you how overload protection logic works on this TV?

[djju]

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

Hi, Bud

I understand what you said. Mainboard won't turn on the BL-ON or something make the mainboard send a command to cut the power for protection.
But I can't understand the which part makes this symptom.
At first, I think an impedance of some part might be almost short to GND, so PMIC sends to command to cut the power source. But no fault part on the main board by visual inspection.

I already did it. Test with disconnection (1) IRDA board, (2) Speaker wire, (3) WIFI daughter board. The symptom was same.

Yes, the TV never stays on long enough for me to see the video or sound after it has gotten a problem.
Almost 1 month ago.

And I check the fuse.

Mainboard F1, F2 is good. It gives 5V and 12V
Power Supply F1 is good. It shows 0 ohm.

[djju]

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

OK, I can see that the PS-ON is gone when the backlighs and the Power LED go out.
'P11 PSON 67.1mV 2.84V -> 67.1mV'
So some how the main board just stops sending out the command signal (the BL-ON (ON/OFF) and DIM are also gone). So it is main board problem or something sends the signal to tell the main board for the TV to turn off.
You may want to try disconnecting all other boards that are connected to the main board one at a time to see if the PS-ON will stay present. I wonder the control panel switch is doing this or the IR board. It acts like some one turn off the TV
BTW, so the TV never stays on long enough for you to see the Video or sound?
History of this TV?

Hi, Bud

I understand what you said. Mainboard won't turn on the BL-ON or something make the mainboard send a command to cut the power for protection.
But I can't understand the which part makes this symptom.
At first, I think an impedance of some part might be almost short to GND, so PMIC sends to command to cut the power source. But no fault part on the main board by visual inspection.

I already did it. Test with disconnection (1) IRDA board, (2) Speaker wire, (3) WIFI daughter board. The symptom was same.

Yes, the TV never stays on long enough for me to see the video or sound after it has gotten a problem.
Almost 1 month ago.