4K Vizio P702ui-P3 No Picture, No power to T-Con

[johnboy1313]

Just picked this set up hoping that it would be the side tab fix that I;ve seen on other 70" TVs. Not the case this time. Part of me is excited about this, part of me is a little disappointed. The set powers on but there is no backlight and no picture. I see 384 volts across the big cap. 12V to the main board is present, as is 24V. There is a pin on the PSU at CN201 labeled, "T-CON_ON". It measures 0V as do the two pins at CN201 labeled 12V T CON and the pins labeled 12V at CN202 which connects to the T-Con. I haven't tried to see if there is a picture with a flashlight but the lack of power to the t-con leads me to believe there isn't.

At this point, I've unplugged the t-con from the main and also tried the t-con connected with the four ribbons to the screen disconnected.

No dice.

[budm]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

The T-CON ON command comes from the main board, >2VDC = ON = 12V feeding the T-CON board.
Vizio 09-70CAR040-00 Power Supply P702UI-B3
http://www.shopjimmy.com/vizio-09-70...upply-unit.htm
SMD switched power P-CH MOSFET Q204 is fed by 12V to the Source pin through inductor L201, the 12V T-CON comes out from the Drain pin, the TCON-ON is fed to turn ON Q202 which then turns on the MOSFET.
Pictures provided by shopjimmy.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

More pics

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

The T-CON ON command comes from the main board, >2VDC = ON = 12V feeding the T-CON board.

Should I try to jump the pin with a resistor? I'm worried that I have one or more failed LEDs on top of whatever is causing the no 12V to the tcon.

[budm]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Should I try to jump the pin with a resistor? I'm worried that I have one or more failed LEDs on top of whatever is causing the no 12V to the tcon.

You should find out if you do have 12V feeding the MOSFET first, since you do not have the T-CON ON command from the main board, do you have AC-DET signal? How about other signal like the BL-ON, is it present?
If you are going to jump the TC-ON on pin with the resistor, you must disconnect that wire going back to the main board first otherwise the main board will keep that line and not allow it to go HIGH.
Can we see the whole back side of the TV? I cannot see how the LED driver board is connected to the other boards.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

I'll get pictures of the entire assembly this evening.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Sorry for the delay. Here is the picture of the entire assembly.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

PS-ON goes high to 5V. AC-DET is high at 3.8V whether on or off. 12V and 24V drop out at power off. Tcon 12V stays solid at zero. With the Tcon on wire pulled from the main, there is still 0V at the main and the PSU pin Tcon ON. With a resistor from PS-ON to Tcon on "12V Tcon" goes high to 12.5V. Still no backlights. I'm wondering if a pin or pins on this connector from the main board below to the LED board above is supposed to go high to turn the leds on. They all stay low. Half at 0V and the other half at several mV.

[budm]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

So at least one signal is dead. Are you getting any DCV on the connector CN301 that goes to the LED driver board?
Vizio Y8386494A LED Driver P702UI-B3
http://www.shopjimmy.com/vizio-y8386494a-led-driver.htm
Pictures provided by shopjimmy.
We need to find out if the LED driver board is getting the BL-ON signal on connector CN101 which is not labeled with any pin names.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Both connectors C101 and C301 have about a 50/50 split between pins that show 0V, which I assume are GND pins, and pins that show less than 1V. The heat sink on the main board gets warm as if it's functioning at some level, and the red optical port lights for a while, but flashes off once every so often as if the set is rebooting. At this point, I'm thinking main board.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

The main LED does in fact light again when the red optical port blinks off. I found a full kit with every board for a price I can live with and a 180 day warranty. Hopefully it is just a board and not an LED inside the panel. I really don't want to have to get into the panel.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Bad news, I got the main board in. The set fired right up and has a bad panel. I opened it up and found a side ribbon folded under the screen from the factory. I carefully pulled it out and found a slice in it. It kinda sucks.

On a side note, can we still attach photos to our posts?

[freakaftr8]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Are there side tabs on both sides of the panel? I know this model doesn't use driver boards on the sides but however the side tabs can be disabled possibly on one side . The test is to disconnect the flat cable off the tcon board to the bad side of the panel. Then power of the TV and see if the side that is still connected has a good picture on that side.

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

And if it does?

[freakaftr8]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

We shall see. If this side driver is in fact rendered useless there is no Repair on the panel. I wonder what would happen these were removed in the same manner that the sharp panels have their problems considering that there's one on each side if there is. One logical way to tell if the panel is going to function properly is to just have the t-con ribbon connected on the good side first see if you have half of a picture. However this picture may be marred by the driver on the other side being smashed I

[freakaftr8]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

As for the attaching photo problem that BadCaps is having at the moment you could probably upload a photo to Photobucket and share a link momentarily

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

We shall see. If this side driver is in fact rendered useless there is no Repair on the panel. I wonder what would happen these were removed in the same manner that the sharp panels have their problems considering that there's one on each side if there is. One logical way to tell if the panel is going to function properly is to just have the t-con ribbon connected on the good side first see if you have half of a picture. However this picture may be marred by the driver on the other side being smashed I

The driver wasn't smashed. The ribbon was cut through about ten traces. Using chip quick, I was able to tin all of the traces after exposing them with the edge of a knife blade. I may try to carefully repair them and paint over the repair with some fingernail polish.

[freakaftr8]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Sweet! Let us know the outcome

[brianc974]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Hi, I have the same set with the exact same problem. No t conn on signal from main board. Under normal circumstances would a main board have fixed the problem? Is it a coincidence that the ribbon cable was damaged also in your case, or did it cause the loss of the t conn on signal somehow? Thanks!

[johnboy1313]

Re: 4K Vizio P702ui-P3 No Picture, No power to T-Con

Under normal circumstances would a main board have fixed the problem?

Yes. I still have the main board somewhere around here.