820-3462 no backlight

bartech

Member
I got problem whit ppbus_sw_lcdbklt_pwr
i got 12,3v on f9700
Q9706
1-0.02
2-0.02
3-12,2
4-12.6
5-0.02
6-0.02
Zrzut ekranu 2021-09-1 o 12.01.47.png
 

2informaticos

Administrator
Staff member
Do you get image for sure?
Else, no reason to search for backlight.

Check at least if voltage appears at pins 28-30 iof J9000.
Did you try known good (compatible) LCD assembly?

BTW, no need to post boardview screenshot, once you post component voltages.
 

bartech

Member
there is apple logo like in no backlight problem ,macbook chime , 0V on J9000 28-30 .
Got 12,6 on f9700
 

2informaticos

Administrator
Staff member
"0V on J9000 28-30"
I didn't read that; impossible to get image in such condition.
Please re-check...
 

bartech

Member
there is 5v but only in few seconds at the start then 0V on 28-30 , there is apple logo but no backlight
 

2informaticos

Administrator
Staff member
"5v but only in few seconds at the start"
LCD_HPD must go high at same time.
If not, PCH cannot detect the screen.

"there is apple logo"
You can't get image without the mentioned voltage!
 

bartech

Member
lcd_hpd is 2,77V on r9000 -leg 1 leg 2 - 0v
on l 9000 there is 4,99 V
LCD_BKLT_EN 3,34v
LVDS_BKL_PWM_R - 3,21v
BKLT_EN - 3,12v
 
Last edited:

2informaticos

Administrator
Staff member
With Apple logo, do you mean the light on top cover?
In such case, backlight is present.

Post C9719 voltage, with LCD connected.
 

bartech

Member
apple logo on lcd but whit no backlight if i use flashlight from the back and light the apple logo i can see no ssd flashing folder so it is working but no backlight like on this photo from internet
 

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2informaticos

Administrator
Staff member
Check the traces between U/Q/D9701 and L9710.
Also check R9708/09, R9717-22 and their traces.
Be sure D9701 is not shorted.
 
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