Apple MacBook Pro A1502 notebook does not recognize Nand repair

Apple MacBook Pro A1502 notebook does not recognize Nand repair

Machine model: apple MacBook Pro A1502

Malfunction: the notebook does not recognize Nand.

Maintenance process:

Apple MacBook Pro A1502(13 models) notebook computer, the notebook can be turned on, and there is a question mark on the screen. After turning on, press option as shown in the figure, but it can enter PE but can’t find Nand.

Apple MacBook Pro A1502 notebook does not recognize Nand repair figure 1.
Remove Nand to another machine for testing.Nand is good, but the problem lies in the motherboard.

Disassemble the machine, take out the motherboard, and make visual inspection without repair or water damage. Open the drawing to measure VCC, which is normal.

Apple MacBook Pro A1502 notebook does not recognize Nand repair figure 2.
The reset signal from U3740 is also normal, and the measurement on is also normal.

Apple MacBook Pro A1502 notebook does not recognize Nand repair Figure 3

Apple MacBook Pro A1502 notebook does not recognize Nand repair figure 4.
This data interface needs to measure the ground values of lighting cable, with 4 groups, all of which are in 314 or so, which is normal.

Apple MacBook Pro A1502 notebook does not recognize Nand repair Figure 5.
Open the SATA module schematic of the bridge, and check the VCC of the bridge, which is only 0.34V.

Apple MacBook Pro A1502 notebook does not recognize Nand repair Figure 6.
This VCC comes from U8005 chip. This chip has VCC and output when it is turned on. Check that its VCC and turn-on are normal, with only 0.89V output, which is not normal.

Apple MacBook Pro A1502 notebook does not recognize Nand repair figure 7.
This VCC was sent to the bridge module VCC through Inductor L1290, and it was measured that VCC had changed here. After dismantling auto power off, it was found that diode value was the back stage VCC, that is, there was VCC on the other side of the bridge.

Apple MacBook Pro A1502 notebook does not recognize Nand repair figure 8.
According to the drawings, there are two Capacitor and a resistor attached to the back of this VCC. First, remove the two Capacitor.

Apple MacBook Pro A1502 notebook does not recognize Nand repair figure 9.
Measuring diode value found that there were more than 200. Put Inductor back and replace it with an Capacitor.

Apple MacBook Pro A1502 notebook does not recognize Nand repair Figure 10.
Connect the power supply installed Nand, connected to the screen and started,Nand recognized it, started normally, troubleshooting, and maintenance ended here.

Apple MacBook Pro A1502 notebook does not recognize Nand repair Figure 11.
Summary:Capacitor C1292 short-circuit current pulls down VCC by 1.5V, resulting in the bridge SATA module not working, thus denying Nand.