Vizio P502UI-B1E No Picture Flashing Standby Light

[R_J]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

If you get a change on PS_ON when you push the power button would suggest the main is at least partly working, and the micro understands the power command and changes the PS_ON pin.
Also note that the plugs CN9101/3 has two rows of pins (14 pins), and CN9101 has 16 pins .
Do you get +24 volts when the power button is pressed?

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

If you get a change on PS_ON when you push the power button would suggest the main is at least partly working, and the micro understands the power command and changes the PS_ON pin.
Also note that the plugs CN9101/3 has two rows of pins (14 pins), and CN9101 has 16 pins .
Do you get +24 volts when the power button is pressed?

I do not have a cn9101/3 connector on the power board. I do have cn9201/cn9203 that has 14 pins. (1st pic below)

Cn9101/cn9102 has 16 pins and has PS_ON and when the set is powered on it has 2.87V. Standing by it gets 80.8mV until power button is pressed when it gets 2.87V.

[R_J]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

I ment cn9101/cn9102. I will just refer to the function and not the plug
So the PS_ON is the white wire? and it changes from .80 (stby) to 2.87 (ON) correct?
When the power supply is tured ON do you get 24 volts?
If you don't get 24 volts, check the voltage on optocoupler ic9103, pin 1 (pin2 should be ground) and see if it changes when the power button is pressed?

[Kickinwing]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

@R_J , Do you have schematics available for these boards?

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

I ment cn9101/cn9102. I will just refer to the function and not the plug
So the PS_ON is the white wire? and it changes from .80 (stby) to 2.87 (ON) correct?
When the power supply is tured ON do you get 24 volts?
If you don't get 24 volts, check the voltage on optocoupler ic9103, pin 1 (pin2 should be ground) and see if it changes when the power button is pressed?

Thank you again for the help, greatly appreciated.

Yes PS_ON is a white wire and yes those readings are correct.

On c9201/c9203 on the 24V pins they all do get 24V when power is on to the power supply.

Ok so on pin 1 of ic9103 when set is turned off I get 250mV and when turned on I get 1.13V. That is all.

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

So does this sound like a faulty main or power board?

[R_J]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

If the power button controls the PS_ON pin, I would say the microprocessor/eeprom seems to be ok, When the PS_ON goes high it turns on the +24 volts on the power supply, so I would say the power supply is ok.
Are you sure you don't have audio from any sources? Try connecting an hdmi source as it can usually tell the tv to switch to the correct source.
When you power on the tv are you sure you don't get a flash of the backlights?

[budm]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

https://www.badcaps.net/forum/attach...3&d=1556588282
So what Voltage do you have on the ON/OFF (BL-ON) pin, and DIM pin when TV is turned on?
Do you also have 12V on the SMD fuse of the T-CON board when TV is turned on?

[R_J]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

I don't think the BL_ON and DIM are used on the power supply, I suspect the main controls the led driver board directly, I don't think his model has wires going to those pins on the power supply
I think the BL_ON control is on the main, CN701 pin 14, BL_PWM is pin 13, but they are likely not used either, I believe the main talks to the led driver via CN805.

[budm]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

https://www.badcaps.net/forum/attach...8&d=1556390413
OK, with better picture now I can see that there are now wires for the ON/OFF and DIM pin.
OP: "have confirmed the set is not running and there is no picture on the screen when using a flashlight so definitely not the backlights."
So right now he does not have backlights, correct? I wonder why OP indicated that "definitely not the backlights".
The MCU should also send the signal to turn on the MOSFET on the main board to supply the switched 12V to the T-CON board.

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

https://www.badcaps.net/forum/attach...8&d=1556390413
OK, with better picture now I can see that there are now wires for the ON/OFF and DIM pin.
OP: "have confirmed the set is not running and there is no picture on the screen when using a flashlight so definitely not the backlights."
So right now he does not have backlights, correct? I wonder why OP indicated that "definitely not the backlights".
The MCU should also send the signal to turn on the MOSFET on the main board to supply the switched 12V to the T-CON board.

IndicAted this because I've seen many posts leaning towards backlight/eeprom issues and I just wanted to let everyone helping know that i did check for an image with a flashlight and there is not one.

I am at work now and will check the inputs tonight when I get home.

[nomoresonys]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

We have learned that it CAN be a backlight issue, EVEN if there is no display on screen wih flashlight, was reminded of this just the other day in a thread here with a successful fix.

[nomoresonys]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

Not saying it is a backlight problem, just saying at least on some tvs it can't be ruled out just cuz theres no image. https://www.badcaps.net/forum/showthread.php?t=67154

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

Ok so I currently have a amazon fire stick connected and turning the tv on with remote or power button doesn’t change a thing. I have tried all hdmi inputs and nothing on the screen at all. I’m using a flashlight again during power on cycle and I do not get any images on the screen. The status light comes on and fades away. EDIT: and no flashes from backlight at all, red light comes on in the optical port.

On cn701 pin 13/14 are both empty cavities on the main board connector.

[R_J]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

You could check CN805 pin 8 on the led driver board and see if you get 5 volts when the tv is turned on
Check the voltage on R8220 (0Ω) next to cn805
CN806 1,2,3,4 should be +V(from power supply) 5,6,7,8 are ground

You can also check the main board cn206 pin 44-51 for panel power (12v)

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

You could check CN805 pin 8 on the led driver board and see if you get 5 volts when the tv is turned on
Check the voltage on R8220 (0Ω) next to cn805
CN806 1,2,3,4 should be +V(from power supply) 5,6,7,8 are ground

You can also check the main board cn206 pin 44-51 for panel power (12v)

Ok I get 5 volts on cn805, r8220.

Cn806 1-4 I get 24 V

I'll check cn206 later I quickly ran my lead over the contacts on the board and never saw 12 volts. May have been going to quickly to leave for work tonoutrun a storm.

Thank you again

[JDMRpr78]

Re: Vizio P502UI-B1E No Picture Flashing Standby Light

Cn206 has such small pins I could only run my positive lead across them and I never saw over 1.5V as the highest reading. I would assume if it is supposed to have 12v something is definitely wrong with my main board?