Macbook Pro A1398(820-3787-A) Backlight problem

hani

Member
i changed the J8300 because there is short in all 5 capacitors C8300 and C7717/18/19/16
I Put Connector from A1466
but the short in the capacitors gone but the backlight problem not gone.
i made my measurements for Voltage on F7700 12 volt -- Q7706 (pin 3 LCDBKLT_EN_L11.7 volt -pin 4 12 v --pin 5,6 changed from 9.6 -7v-5-v-to 2-volt and also on D7701 the same . PPVOUT_S0_LCDBKLT 0volt---PP5VR3V3_SW_LCD_UF 5volt
on Q7706 pin 1234 0volt but pin 5 go down fom 9 to 2 volt also
on U7750
Pin 2 BKLT_SCL_R 4.7 volt ---- Pin 4 5volt---Pin 5 BKL_1_SDA 3.2 Volt---Pin 6 BKL1_SCL 3.2 volt---Pin 7 2.4 volt--Pin 8 0.4 volt Pin 11 5volt Pin 10 0 volt

on U7701
Pin 2 -0volt , pin 5 -5volt , pin 9 -12.6 volt , pin 11-11volt , pin15 -4.7 volt , pin 16 4,7 volt ,pin 18 - 5 volt , pin 17 - 0 volt.
all the measurements without screen
if the problem from q7706-- can i use one from A1466
 
Last edited:

2informaticos

Administrator
Staff member
"on Q7706 pin 1234 0volt but pin 5 go down fom 9 to 2 volt also"
As per schematics, pins 1, 2, 5, 6 are tied together.
However, irrelevant measurments, as pin 3 doesn't go low.
BKLT_SD opens Q7706, when goes to 0V.

Do you get LCD_BKLT_EN?
 

2informaticos

Administrator
Staff member
11.7V at LCD_BKLT_EN (R7742)???
Are you really sure?
Please, check schematic and post usefull information.
 

hani

Member
update
LCD_BKLT_EN -- 0volt without screen
3.3 volt with screen

PPVOUT_S0_LCDBKLT -- 52 volt
PP5VR3V3_SW_LCD_UF--5 volt
until now there is no backlight on the screen just the image without light.
Pram reset done --but not solve the problem.
there is usb activity in the board
 

2informaticos

Administrator
Staff member
"PPVOUT_S0_LCDBKLT -- 52 volt"
Open LED strip.
Check LCD connector, video cable and LCD display.

Test full COMPATIBLE LCD assembly first.
 

hani

Member
update
test with new lcd from the same model and nothing changed
i change also j8300 and the same problem ( J8300 compatible with A1466)--(is it ok??)
i have these voltage
LCD_BKLT_EN -- 0volt without screen
3.3 volt with screen

PPVOUT_S0_LCDBKLT -- 52 volt
PP5VR3V3_SW_LCD_UF--5 volt

until now there is no backlight on the screen just the image without light.
Pram reset done --but not solve the problem.
there is usb activity in the board

any help ?
 
Last edited:

2informaticos

Administrator
Staff member
"PPVOUT_S0_LCDBKLT -- 52 volt"
LED strip is open circuit!!!
Normal voltage is 40V aprox...

Did you check voltage direct on J8300?
Clean internal contacts.
Get another new connector.
 

hani

Member
direct also 52 volt
my question about the j8300 connector
i use one from a1466 -is it the same connector?
what about important signal to the screen need to measure also?
 

2informaticos

Administrator
Staff member
Both connectors have 30 pins, be sure to get good contacts inside.
If you get 52V at backlight rail, then the screen is correctly recognized; no need to check other pin voltage.
There should be image already.
 
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