820-00165 - no backlight

[nelo1012]

hey guys, '

i have a 820-00165 that has no backlight i have already replaced backlight filter (F7700), have also replaced LP8550, LCD Connector, Q7707, and nearly everything else around there, and back of the board,

and i know i should try to understand it, but i have spent hours on it and nothing, i still believe is something simple but you guys please help!


q7706

1- 8.6
2- 8.6
3- 2.82
4- 8.6
5- 8.6
6- 8.6

q7707

1- 0
2- 3.3
3- 0
4- 0
5- 3.3
6- 0

F7700

8.6 on both sides

thank you in advance

 

[2informaticos]

Post voltage on both pins of D7701.
Check XW7720 bridge integrity.
Use search function on the forum; pictures available too...

 

[arash]

Maybe its the Panel.. Have you tested it with a known good one ?

 

[nelo1012]

D7701 - 8.58V on both sides

Known good Panel/display

 

[2informaticos]

Post some voltages dor U7701; VIN; VDDIO, EN, PWM.
Use surrounding components as test points.

Did you check XW7720?

 

[nelo1012]

PWM - 0.57
EN- 2.83
VDDIO- couldnt find it
VIN- 8.58

and pardon my stupidity, but dont know how to check XW7720, i see it on the board view,

 

[2informaticos]

"Use search function on the forum; pictures available too..."
https://boards.rossmanngroup.com/search?q=xw7720&searchJSON={"keywords":"xw7720"}

Remove R7704 and run a wire from BKL_EN to BKL_PWM.
If you get backlight, do PRAM reset few times.
Remove the wire, resolder R7704 and test again.

 

[nelo1012]

i removed R7704 and ran wire from BKL_EN to PWM, and no backlight, did reset pram a few times, and nothing,

also checked XW7720 , D7701 pin 1 to U7701 Pin 5, and there is continuity, so i think bridge integrity is ok,

 

[2informaticos]

Post resistance to ground on all U7701 connections.
That will denote a bad solder, if is the case.
Do you get image?

 

[vsa100]

edit...wrong trhead...sorry.

 

[2informaticos]

Use diode mode, instead of ohm scale; red probe at ground.
And post values for LED_RETURN_x lines.