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820-4924 Backlight Problem

M

mushr00m

Member
Hello guys

I have this Macbook Pro 820-4924 which doens't have image/backlight. Below are some measurments


SMC_LID = 3.38v
PPBUS = 12.53V


Q7700
1 = 0V
2 = 0V
3 = 12.43
4 = 12.53
5 = 0V
6 = 0V


DIODE MODE READINGS PIN 3/4 LCD CONNECTOR 0.484v

REPLACE THE IC WITH A KNOW GOOD ONE STILL NO BACKLIGHT

BKLT_EN_R = 0V
I2C_BKLT_SCL = 5.15V
I2C_BKLT_SCA = 5.15V


R7731 = 12K
R7732 = 150K

R7753 = 1.6K
R7752 = 1.6K


Know Working Display (From A1425 ) tested and same results
 
2informaticos

2informaticos

Administrator
Staff member
"doens't have image/backlight"
No reason to expect backlight, if no image confirmed.

Do you get external video, USB activity, or chime at least???
 
2informaticos

2informaticos

Administrator
Staff member
So the board boots.
But, as I said, backlight appears AFTER internal image.

Check for voltage at pins 5, 9, 28 of J8300; in the first few seconds, when hear the chime.
 
2informaticos

2informaticos

Administrator
Staff member
"pin 9 = 1.01V"
It should be 2.5V aprox and DP_INT_HPD reaches 3V.
Test with compatible LCD assembly.
 
M

mushr00m

Member
Got it.
According to those measurements do you think is it BAD display? Or still could be a logic board problem?
 
2informaticos

2informaticos

Administrator
Staff member
You should test with good LCD.
Just in case, check DP_INT_HPD level.
5V remains always at pins 28-30 of J8300?
 
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