XBR-55X850 turns on but no pic no 12v on t-con

[hmendez86]

Got this tv 4k sony xbr55x850c evrything works you can heard sound but no pic....i check the t-con for 12v and theres none....there no backlight.....if i try look the screen with flashligth theres no image ether......anyone had trouble with these tvs

[budm]

Re: XBR-55X850 turns on but no pic no 12v on t-con

https://www.badcaps.net/forum/attach...0&d=1525751962
Picture is not clear, I cannot read the pin out of that large white connector, I also cannt read the power supply board P/N as printed on the white sticker.
Please upload good clear pictures of the boards, you will get lots more help that way.
We will need the Voltage readings of all those pins of those 3 connectors.
You need to put down pin name and follow by the Voltage reading when TV is not on and when power switch is activated.

[nomoresonys]

Re: XBR-55X850 turns on but no pic no 12v on t-con

Did you check the two fuses F1 and F2 on the tcon?

[Davi.p]

Re: XBR-55X850 turns on but no pic no 12v on t-con

Check the mainboard, usually near the lvds connector there are one or two power mosfets that enables Tcon supply rail, check them. Maybe with the no communication between mainb. - screen the mainboard deactivates also the back light, not so probable but worth a try no?

[budm]

Re: XBR-55X850 turns on but no pic no 12v on t-con

https://www.badcaps.net/forum/attach...1&d=1525751962
The power for T-CON on this TV is not from the main board, it is supplied from the power supply board via small 5-pin connector on the T-CON board.

[freakaftr8]

Re: XBR-55X850 turns on but no pic no 12v on t-con

Is the LED in front of the tv under the Sony emblem white or flashing m green/amber?

[Davi.p]

Re: XBR-55X850 turns on but no pic no 12v on t-con

Anyway if it's only from the psu, it can still be delayed so a couple of transistor may activate it at the right moment.

[R_J]

Re: XBR-55X850 turns on but no pic no 12v on t-con

On the power board CN6401, pins 25-28 are tcon_vcc12v. Pin 24 is TCON_ON control. Q6403 should be the fet that controls the tcon 12 volts. which comes from the reg12v. I cant tell for sure but it looks like Q6404 is the transistor that controls the fet
Also note there are a lot of small fuses on the main board, IE: F9403, F9406, F9401, F9002, F9000, F7700, F9009, F8400 etc. they may be worth checking

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

I check for the small sdm fuses on main board an all are ok

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

The amber ligth is white were the tv is on i can heard the sound...

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

The t-con power comes from the power supply..but but the swicth to turn on the t-con and back ligth comes from the main board....what i think is the problem a transistor on main is damage.

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

[budm]

Re: XBR-55X850 turns on but no pic no 12v on t-con

So is the power supply board getting the control signal on 'Pin 24 is TCON_ON control'?

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

It has a signal but not all 12v .....on the pin 15 has 12v..what i did to power i jump starter the power on to 5stb...but i wont get 12 on t con

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

I had a similar problem on a another tv xbr55x810c i was thinking the problem was t con because the re were no 12 on tcon from power.....so i change the power to a new one but no luck. so i was thinking were i go now? To i dicide to change main board and it worked leds ligthup and 12 v on power....

[freakaftr8]

Re: XBR-55X850 turns on but no pic no 12v on t-con

I'd try formatting a USB and go to Sony website and unzip the eeprom ro the USB. With tv unplugged insert USB and plug tv in. Wait till flashing white indicator stops and tv resets. About 30 to 45 min process.

Could be corrupt eeprom. Had this happen when I was trying to figure out my XBR-75x850c.

[budm]

Re: XBR-55X850 turns on but no pic no 12v on t-con

For T-CON to get the power from the power supply board, the main board has to send TCON_ON signal, the PS-ON signal for turning on the main switched supply, that is why we are asking if you do have the TCON_ON signal or not.

[hmendez86]

Re: XBR-55X850 turns on but no pic no 12v on t-con

Tcon-on pin i get 0.005

[budm]

Re: XBR-55X850 turns on but no pic no 12v on t-con

That means the main board is not sending the signal to turn on the power supply circuit to provide 12V to the T-CON board.
Sounds like you are having the same problem as in your post #16.