Apple Macbook Air A1932 Notebook no booting

Machine model: apple Macbook Air A1932

Malfunction: Notebook no booting

Maintenance process:

I received an Apple MacBook Air A1932 notebook computer, which is Previously repaired computer. It will not be boosted and will not be online after recovery.

The current of bare board is somewhat high without boosting, and the periphery of CD215 chip and Short circuit chip of U7800 PMU are not measured.

Apple Macbook Air A1932 Notebook no booting Figure 1.

When the current is set at 279mA,infrared Camera is used to detect and observe that T2 is obviously high temperature, and it is confirmed that there may be a fault in T2.

Apple Macbook Air A1932 Notebook no booting Figure 2.

After plug-in, the CD3215 should send out three LDO VCC 3.3v 1.8 v1.1v, and then send it to the charging IC9240HI chip through the isolation tube to complete the first step-up 12V generation. At this time, the presence of VCC at the common point does not mean that the step-up of the CD3215 is completed.

After there is VCC in common, continue to generate PP3V3_G3H_RTC_R to cd3215 V CC. At this time, PMU U7800 starts to work and successively outputs VCC such as 1.8SLPS 2RP1.1pp3V3Awake 0.82V0.9V to T2 VCC, T2 starts to work with internal configuration rom and external ROM, and T2 chip is turned on through I2C SCL SDA bus. Continue to trace the auxiliary circuit of T2, and inquire step by step according to the time sequence.

Check that T2 does not have Short circuit, and trace that the waveform of T2 plug-in BIOS is normal.

Apple Macbook Air A1932 Notebook no booting Figure 3.

Rom has started to work, and T2 has also turned on the CD3215 I2C bus with 1.8v waveform and VCC. In this case, replace the CD3215 chip directly, and replace the two chips together, which can boost the voltage and start up normally,Normally booting up.