Sony Bravia XBR-75X850D

[m4a2t0t]

This TV does not power on. No standby or power light

The left side power board seems to be the issue. The large primary caps have .9v on them. The rectifier has 2.5V across the AC terminals.

On the first board (left most board), If I measure from Neutral to the rectifier bottom AC pin I get 2.3V, top pin 150mV, Live to bottom pin 120V, live to upper 122V.
If I compare it to the second board I get Neutral to bottom 1.1V, upper 121V, Live to bottom 121V, upper 1.1V.

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

The rectifier wont work until RL801 is turned on, correct? Im actually reading 12.7Vdc on both sides on the relay. Shoudlnt I see 12.7 across it, or 12.7v on one side and 0 on the other, when its on? I did remove it from the board and it turns on when 12V is applied and the switch side has about .5 ohms.

[petehall347]

Re: Sony Bravia XBR-75X850D

what you describe is looking like whatever drives the relay isnt doing its job for some reason .

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

I thought the left one was the main power board but it isnt.

I will go through the flow chart checks tomorrow and see if that narrows it down

[nomoresonys]

Re: Sony Bravia XBR-75X850D

How bout a picture of the whole back as to see how everything is connected.

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

Added backside picks of power supplies

I went through the flow chart test and im stuck on the last part of the U-COM failure test

If BL_MUTE (R9090) is 0V, Check BL_ON IC9017 pin 18. Is voltage greater then 3V

R9090 is 3.4V and pin 18 is 0v. Not sure what im supposed to do. Should i continue to the DDCON tests?

I added the pic of the IC. R9090 is connected to the 3 pin IC to the right of the 20 pin IC9017

[nomoresonys]

Re: Sony Bravia XBR-75X850D

.

[lotas]

Re: Sony Bravia XBR-75X850D

IC9017 is a programmed microcontroller from MICROCHIP and it contains its own firmware.

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

DDCON CHECK

3.3v_main, 1.1v_sagi, 1.5v_sagi,5v_main, 1.0v_hdmi, 1.8v_tu, 1.0V_muf, 5.0V_vbus, 1.5v_ddr, all present

The DDCON check was in 2 parts for some reason. IC9001 Vcc on C9033, greater than 12V - Yes, 12.7. Check Vcc on C9061, greater than 4V - Yes, 4.8V. Check enable pin on IC9010 pin 1, greater than 2.5V, yes, 4.8V. If yes, change DDCON IC9009. That IC is for 1.5V_DDR and it is present on the large coil on the output. Why would it have me change that IC if its outputting a voltage?

None of these tests actually had me check the output of any of these ICs. Check input, greater than 12V? check enable pin, greater than 2.5V? Not one check of the actual output voltage. According to this flow chart I need to swap every DDCON and LDO even though they are working fine.

LDO CHECK

1.8V_agi, 2.5v_agi, 1.05v_muf_a, all present

There is nothing left to test for no power. Am I looking at a set with bad firmware or SoC on one of the boards? Or is it an issue with that BL_MUTE signal being 3.5v?

[nomoresonys]

Re: Sony Bravia XBR-75X850D

Added backside picks of power supplies

I went through the flow chart test and im stuck on the last part of the U-COM failure test

If BL_MUTE (R9090) is 0V, Check BL_ON IC9017 pin 18. Is voltage greater then 3V

R9090 is 3.4V and pin 18 is 0v. Not sure what im supposed to do. Should i continue to the DDCON tests?

I added the pic of the IC. R9090 is connected to the 3 pin IC to the right of the 20 pin IC9017

Can you post the manual or flowchart, whatever you're working with, so we can see what you are referring to.

[xedap1998]

Re: Sony Bravia XBR-75X850D

This TV does not power on. No standby or power light

The left side power board seems to be the issue. The large primary caps have .9v on them. The rectifier has 2.5V across the AC terminals.

On the first board (left most board), If I measure from Neutral to the rectifier bottom AC pin I get 2.3V, top pin 150mV, Live to bottom pin 120V, live to upper 122V.
If I compare it to the second board I get Neutral to bottom 1.1V, upper 121V, Live to bottom 121V, upper 1.1V.

Most likely the board D is bad....the EMMC chip on board D need to be replaced

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

Sorry about the delay in responding. I tried uploading the service manual but it kept failing.
Try this https://file.io/aLjSiwodasQ7

If TCON VCC is not present will that cause any of this? I do not have BL_ON, PWR_ON TCON_ON when pressing the power button. If I jump power from standby 3.3 to BL_ON, PWR_ON I can hear the relay in the secondary PSU turn on and I have voltages present on the backlight pins.

I swapped the BM1 board and DSP board from units with cracked panels and still no change

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

Added flow chart I was following

Is there anything else that could cause a dead set? The flow chart for the G boards is 2 steps.

Standby on DPS - check
Standby on BM1 - check

Means B board issue

Is the BM1 board I bought bad?

The BM1 board power_on line is at 3.38V and stays there when the power button is pressed. Should it go to 0?

BL_ON, PWR_ON, TCON_ON all missing. Power button has 3.3V and drops to 0 when power button pressed.

[EazyBone]

Re: Sony Bravia XBR-75X850D

Have you jumped tcon on/blon/power on/stby with main board disconnected? To then test voltages? Maybe verify this procedure before doing it as I'm newer, but does that turn bl on? Give tcon power etc

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

When I do that I can hear the relay in the BL power board turn on and I get voltage at the BL pins but I dont see the backlight turn on.

EDIT: Actually I think I only did bl_on and pwr_on. I will go try it again with tcon_on as well.

EDIT2: When I jump those lines I get 72V on the backlight pins but the backlights do not appear to be on.

Does anyone know more about the power on signal in sony tv's? My pwr_on signal is 3.3v, its 3.3v immediately after plugging in power and stays the same when I press the power button. Am I missing something about that signal? Shouldnt it change when I press the button?

[EazyBone]

Re: Sony Bravia XBR-75X850D

Make sure you have main board disc from LED driver also

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

I tried with it disconnected and the BL board still turns on

[EazyBone]

Re: Sony Bravia XBR-75X850D

I tried with it disconnected and the BL board still turns on

Like the LED on the bl board turns on?

Have you taken both power boards out and inspected the backs for anything burnt. And when you jump tcon on, does the PSU send the 12v to tcon. 12v both sides of tcon fuse?
Need to rule out the PSU boards then can probably confirm is probably main board and can maybe run some tests on that

[m4a2t0t]

Re: Sony Bravia XBR-75X850D

The main board only connects to the G1 power board. I thought you meant to remove the BL connectors from the GL2 power board (backlight board). I just removed the connector from the main board and jumpered the wires while both power boards were connected to each other.

I see nothing visibly wrong with anything on either power board. The TCON does get 12V and its present on both sides of the fuse.

[EazyBone]

Re: Sony Bravia XBR-75X850D

Give us a picture of the whole back to show all boards

The pic 4 in original posts clearly shows 2 ribbons and 1 wire harness connected to LED driver.

Disconnect any combination of ribbons/harness and do the same jump and try and get those bl to turn on. Disc from LED driver side and make sure PSU and main are never connected so a ribbon doesn't accidentally short while disconnected.