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

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).

[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

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.

[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.

[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

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

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

Not at all, Don't mention it.Thanks for your help.

I examined LAMP trace today morning. Please refer the attached picture.
RED is LAMP Line
Black is GND
YELLOW is after Diode 718. not 714

LAMP trace isn't connected OpAMP LM2904. It's GND pattern.

[budm]

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

So if you Ohm out between pin 13 and the Cathode of D718, shows 0 Ohm, right?
If that is the case, then the power supply board is the source sending the HIGH to pin 13.

[djju]

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

So if you Ohm out between pin 13 and the Cathode of D718, shows 0 Ohm, right?
If that is the case, then the power supply board is the source sending the HIGH to pin 13.

Yes, from pin#13 to Cathode of D718 is connected by PCB pattern only, i.e 0ohm. In that case,,, power supply sends 3V to main board and the anode of D718 is connected to the base of Q724. Therefore, in that case, power supply may detect the problem by itself and send the alarm to mainboard?

[budm]

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

That is Collector not Base. PIN OUT: E-C-B. So what DCV do you have on that Anode (Collector of the transistor)?
How about post 23?
The backlights stays on so unless the detection circuit is at fault and thinks that the there is backlights problem even though the backlights stay on.
Or the fault is on the main board and cause the main board to shutdown the PS-ON signal, that is why I suggested what to do in post 23 to narrow down the cause, we already know now that the power supply and the inverter circuits are OK.

[budm]

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

SOT-23:
http://dangerousprototypes.com/docs/File:NPN2.png
http://www.talkingelectronics.com/pr...eMount-P1.html

[djju]

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

That is Collector not Base. PIN OUT: E-C-B. So what DCV do you have on that Anode (Collector of the transistor)?
How about post 23?
The backlights stays on so unless the detection circuit is at fault and thinks that the there is backlights problem even though the backlights stay on.
Or the fault is on the main board and cause the main board to shutdown the PS-ON signal, that is why I suggested what to do in post 23 to narrow down the cause, we already know now that the power supply and the inverter circuits are OK.

Yes, you are right. I confused a pin out. It's my mistake.

[djju]

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

That is Collector not Base. PIN OUT: E-C-B. So what DCV do you have on that Anode (Collector of the transistor)?
How about post 23?
The backlights stays on so unless the detection circuit is at fault and thinks that the there is backlights problem even though the backlights stay on.
Or the fault is on the main board and cause the main board to shutdown the PS-ON signal, that is why I suggested what to do in post 23 to narrow down the cause, we already know now that the power supply and the inverter circuits are OK.

Hi, Bud.
Before the experiment of post 23, I have a question about it.

In a summarization:
1. LAMP is out of power b/d => (True: 'cause it is connected to cathode of diode)
2. 5V, 12V generation has no problem => (True)
3. Inverter has no problem => (True: 'cause it stays on when PSON & ON/OFF are 5V pulled up forcibly)
4. LAMP is low when PSON & ON/OFF are 5V pulled up forcibly. => (??? Which part makes LAMP be low in power supply board?)

Let's make an assumption:
1. Power board has no problem.
2. LAMP:LOW is normal sign (no problem).

If PSON & ON/OFF are on by 5V pull-up with cable cut, power will stay to supply 5V and 12V even though main board detects an error and will try to cut the power to protect the circuit. If it do so, it could affect a demage to main board or power board?

Is it correct?

[djju]

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.

Result of post#23: https://youtu.be/6V7tXe7iCeY

1.cut wires of PSON & ON/OFF
2.measure LAMP (power supply and main board side both)

R1. power on and backlight on
R2. DCV of LAMP goes over 2V and immediately power & backlight off.
R3. At that time, no power_white_led is no blinking.
R4. No more stays than no cut off PSON & ON/OFF wire. Immediately power & backlight off after on.

[budm]

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

4. LAMP is low when PSON & ON/OFF are 5V pulled up forcibly. => (??? Which part makes LAMP be low in power supply board?): There should be a pull-up resistor (since the circuit is the source Voltage) connected to the Collector, and another end of the resistor is connected to VCC (should be 5V), you can also check the Voltage at the Collector when that transistor is OFF to see how high it is.

If PSON & ON/OFF are on by 5V pull-up with cable cut, power will stay to supply 5V and 12V even though main board detects an error and will try to cut the power to protect the circuit. If it do so, it could affect a demage to main board or power board? You already forced on the power supply and the Inverter circuits and it stays on and working without going into shut down. The power supply has its own over current protection circuit so it will go into shutdown by itself if the loads try to draw too much current. The inverter circuits also have over current protection to detect if the lamps are drawing too much current due to age, it also has protection if the high Voltage is applied and the lamp/lamps do not stay on then it will go into shutdown, this is the typical signal that most TV will use to tell the main board that there is problem with the lamp and tell the main board that the inverter circuit is in shutdown mode, most TVs do not have this function since the inverter will be in safety shutdown already and no need to tell the main board that the inverter is shut down since you can see that the screen does not light up.

If PSON & ON/OFF are on by 5V pull-up with cable cut, power will stay to supply 5V and 12V even though main board detects an error and will try to cut the power to protect the circuit. If it do so, it could affect a demage to main board or power board? Well that is why you have to find out if the PS-ON goes low due to the problem on the main board, or due to the lamp signal (but you can fool the main board to make it thinks the LAMP signal is OK), so if the lamp signal is the one that cause the main board to shutdown, nothing on the main board will be damaged, it is the power supply board will be the one that will be damaged, but we already know that the inverter and the power supply are working. If the main board draws too much current due to problem on the main board then the stby power will protect itself by shutting down and restart (it will stay in that loop until the fault is removed).
So if you worry about the main board being damaged (it is already bad in that case) then you can buy a new board and power supply board instead.

[budm]

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

Result of post#23:

1.cut wires of PSON & ON/OFF
2.measure LAMP (power supply and main board side both)

R1. power on and backlight on
R2. DCV of LAMP goes over 2V and immediately power off.
R3. At that time, no power white led is no blinking.
R4. No more stays than no cut off PSON & ON/OFF wire. Immediately power & backlight off after on.

R2. DCV of LAMP goes over 2V and immediately power off. But the backlights stay on, right? it should.

[djju]

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

R2. DCV of LAMP goes over 2V and immediately power off. But the backlights stay on, right? it should.

No, backlight goes off as well. Sorry for no enough information. I have edited and uploaded youtube.

[budm]

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

No, backlight goes off as well. Sorry for no enough information. I have edited and uploaded youtube.

That does not make sense because you have the PS-ON and the BL-ON no longer connected to the main board (wires are disconnected) and those ywo pins on the power supply board are being held high by the two 1K resistors to keep the power supply and the backlights inverter on.
Unless the Dim control line which is still connected goes down to 0V, that will cause the backlights to be off too.
When you were testing the power supply board using the resistor, no wires between the power supply and the main board, right? So the dim wire was also not connected.

[djju]

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

That does not make sense because you have the PS-ON and the BL-ON no longer connected to the main board (wires are disconnected) and those ywo pins on the power supply board are being held high by the two 1K resistors to keep the power supply and the backlights inverter on.
Unless the Dim control line which is still connected goes down to 0V, that will cause the backlights to be off too.
When you were testing the power supply board using the resistor, no wires between the power supply and the main board, right? So the dim wire was also not connected.

I'm sorry, but it's true. Please see this youtube link. http://youtu.be/6V7tXe7iCeY
You can see power & backlight off immediately after power on & backlight on.
And check the picture. I cut PSON & ON/OFF wires.
In my case, I use 3K instead of 1K which I have. (I think it's no problem)

When I was testing the power supply using the resistor, no connection to main board and putting resistor between 5V--PSON & 5V--ON/OFF. No connection for other signals.

[djju]

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

That does not make sense because you have the PS-ON and the BL-ON no longer connected to the main board (wires are disconnected) and those ywo pins on the power supply board are being held high by the two 1K resistors to keep the power supply and the backlights inverter on.
Unless the Dim control line which is still connected goes down to 0V, that will cause the backlights to be off too.
When you were testing the power supply board using the resistor, no wires between the power supply and the main board, right? So the dim wire was also not connected.

Hi Bud,

Please see this video. http://youtu.be/kkaOQi8KWz8

1. Power & baclight are on as long as power is supplied without connection to main board and with 3k pullup on PSON & ON/OFF

2. With connection to main board and 3k pullup on PSON & ON/OFF with cutting wire, then power supplied. Power & backlight was on almost less than a second and off both immediately.