Sony 55X8500E no power

[wumeow]

Hi folks,

I have a Sony 55X8500E that has no power at all, not even standby light.

Tried to jump pin5 and pin9 on the power board with a 1K resistor and got the following measurements.

CN6801
Pin 1 : 0V
Pin 2 : 77.39V
Pin 3 : 77.39V
Pin 4 : 77.39V

CN6802
Pin 1 : 0V
Pin 2 : 0V
Pin 3 : 1.52V
Pin 4 : 1.49V
Pin 5 : 1.49V
Pin 6 : 1.45V
Pin 7 : 1.49V

CN6401
Pin 1 : 0V
Pin 2 : 0V
Pin 3 : 0V
Pin 4 : 0V
Pin 5 : 3.5V
Pin 6 : 0V
Pin 7 : 0V
Pin 8 : 2.8V
Pin 9 : 3.4V
Pin 10 : 0V
Pin 11 : 0V
Pin 12 : 0V
Pin 13 : 12.7V
Pin 14 : 12.7V
Pin 15 : 12.7V
Pin 16 : 12.7V
Pin 17 : 12.7V
Pin 18 : 12.7V
Pin 19 : 0V
Pin 20 : 0V
Pin 21 : 0V
Pin 22 : 0V
Pin 23 : 0V
Pin 24 : 0V
Pin 25 : 0.08V
Pin 26 : 0V
Pin 27 : 0.08V
Pin 28 : 0.08V

C800A
391V

Any help would be appreciated.

Thank you.

[nomoresonys]

Re: Sony 55X8500E no power

maybe check Q123, see if one leg is shorted to either of the other 2.

[nomoresonys]

Re: Sony 55X8500E no power

you have voltage on pin 8, I think that means a backlight issue.

[nomoresonys]

Re: Sony 55X8500E no power

can you post some good straight on pictures of each board and one of the whole back, as to see how everything is connected.

[wumeow]

Re: Sony 55X8500E no power

maybe check Q123, see if one leg is shorted to either of the other 2.

Thanks for your reply.
I checked no short on Q123.

[wumeow]

Re: Sony 55X8500E no power

you have voltage on pin 8, I think that means a backlight issue.

Just tried to ground the pin 8 but nothing happened.

[wumeow]

Re: Sony 55X8500E no power

can you post some good straight on pictures of each board and one of the whole back, as to see how everything is connected.

Here you go.

[wumeow]

Re: Sony 55X8500E no power

Here is the service manual I found online

[nomoresonys]

Re: Sony 55X8500E no power

some of those solder joints look a little suspect, examples of bad joints there: https://www.google.com/search?q=bad+...ih=607&dpr=1.5

[wumeow]

Re: Sony 55X8500E no power

Had a detailed look, can't find any bad solder joints.
Would you mind to point out the component number which looks suspicious?

On the other hand, tested all 6 black light strips light up without any problem? Is it possible the 2.8V I get from BL_ERR is indicating something else?

Much appreciated.

[nomoresonys]

Re: Sony 55X8500E no power

after confirming solder joints are ok, do this test:
Check STBY 3.3V
C518
near CN400
on B* board which is also known as the mainboard.

[nomoresonys]

Re: Sony 55X8500E no power

look closely at the joints, see how some look cracked, a good joint does not look cracked or sparse or a big round glob.

[wumeow]

Re: Sony 55X8500E no power

after confirming solder joints are ok, do this test:
Check STBY 3.3V
C518
near CN400
on B* board which is also known as the mainboard.

Will double check all the solder joints. Thanks

C518 is showing 3.5v.

[nomoresonys]

Re: Sony 55X8500E no power

ok, looks like that points to a problem with the B board/mainboard.

[nomoresonys]

Re: Sony 55X8500E no power

the solder might be ok, hard to tell from the picture, it looked like maybe some of the diode D75x might be a little cracked but not sure.

[wumeow]

Re: Sony 55X8500E no power

ok, looks like that points to a problem with the B board/mainboard.

With 1K resistor jumping the 3.3V standby and power on pin. Power board is still not producing 24V on CN6401 pin25, 27 and 28.

Does it mean both main and power board are faulty?

[wumeow]

Re: Sony 55X8500E no power

the solder might be ok, hard to tell from the picture, it looked like maybe some of the diode D75x might be a little cracked but not sure.

Resolder those Schottky diodes but nothing changed

[wumeow]

Re: Sony 55X8500E no power

Just found a short on ZD905 near IC901. Not sure is this related to the VCC 12V missing.

[lotas]

Re: Sony 55X8500E no power

The zener diode is in parallel with low-resistance resistors, so it seems to you that it is short.

[nomoresonys]

Re: Sony 55X8500E no power

With 1K resistor jumping the 3.3V standby and power on pin. Power board is still not producing 24V on CN6401 pin25, 27 and 28.

Does it mean both main and power board are faulty?

in some cases you need to jump power-on, bl-on, and maybe all the pwm pins to stndby to get the backlights on.