MacBook Pro 15-Inch "Core i7" A1707 EMC 3072 - brak podświetlenia matrycy

Model: Apple MacBook Pro 15" A1707 EMC 3072
PCB P/N: 820-00281-10

Laptop staruje obraz jest widoczny ale brak jest podświetlenia matrycy. Proszę o pomoc w diagnozie.
Pozdrawiam

Hello!

Check the fuse F8400 (F3A, pacakage 0603).
If it is okay, measure the voltage to ground on pin 2 of diode D8410.

bezpiecznik F8400 jest ok, 0V na pinie numer 2 diody D8410

Measure the voltages to ground on pins 5, 9, 11, 15, 16, 17, 18 of chip U8400, when the machine is turned on.

Measures of U8400
5-5,1V
9- 12,65V
11-9.65V
15-4.5V
16-4,46V
17-3,3V
18-5.1V

Measure the voltages to ground on pins 1, 3, 4 of transistor Q8400.

Measure of transistor Q8400.
Pin1-0,03V
Pin3-11.89V
Pin4-12,16V

Measure the resistances to ground on both pins of diode D8410.

Measure the voltage to ground on pin 1 of resistor R5171.

Resistance do ground of diode D8410
Pin1-1,2M Ohm
Pin2-2,4 Ohm
Voltage to ground on pin 1 of resistor R5171 - this place is empty
Pin1-3,4V
Pin2-3,4V

SPIOH1979 hat geschrieben:Resistance do ground of diode D8410
Pin2-2,4 Ohm

It is a short circuit to ground on "PPVOUT_S0_LCDBKLT" power rail.
Did you measure this resistance with the screen disconnected? If so, perform a short circuit test described here on power rail "PPVOUT_S0_LCDBKLT".

It is most likely damaged one of the filer capacitors C8460-C8473.

Yes I measured resistance with the screen disconected.
Can You explain step by step what to do please I am warry will burn something.

Set your laboratory power supply to 12V and set the current limit to 1A. Turn off the laboratory power supply.
Use a copper wires with a cross section at least 1mm^2 and connect + of the laboratory power supply to the power rail "PPVOUT_S0_LCDBKLT" (for example pin 1 of capacitor C8469) and - of the laboratory power supply to the ground (for example pin 2 of capacitor C8469). Turn on the laboratory power supply and slowly increase the current limit until you feel the heat on some component.
You will most likely feel the heat on one of the capacitors C8460-C8473.

Can you tell me how high to go with the voltage. I reached 16V but nothing gone to be heated

SPIOH1979 hat geschrieben:I reached 16V but nothing gone to be heated

What electrical current flows from the laboratory power supply at 16V?

0A

Remeasure the resistances to ground on both pins of diode D8410.

Resistance do ground of diode D8410
Pin1-1.3M Ohm
Pin2- 178.5k Ohm
Why is so different like before ? Now I have the board on the table but both measures I did with the screen disconected.

Connect the screen to the motherboard and remeasure the resistance to ground on pin 2 of diode D8410.
If the resistance will be still high (in kΩ range), turn on the machine and check, if the backlight works.

I am so sorry Matic I waste your time. I did measure with the screen connectd before. When I connected the screen resistance on pin 2 of the diode D8410 droped to 2,4 Ohm. So , Is it mean the screen is faulty ?

The short circuit is most likely on highlighted "Screen board".


Unscrew this board from the housing that it will hang freely in the air and disconnect the highlighted two backlight cables. Be careful not to tear the adjacent wide cables because they are permanently connected to that board.


Then check, if the short circuit to ground is still present on pin 2 of diode D8410, when the "Screen board" is connected to the motherboard.