Apple MacBook Pro a1706 notebook is not powered on for repair

Machine model: apple MacBook Pro A1706

Main board version number: 820-00932

Fault: Notebook no booting is not charged.

I received a MacBook Pro A1706 notebook computer, which is Previously repaired computer, without boosting or charging. I changed a set of CD3215 chips before.

Apple MacBook Pro a1706 notebook is not powered on for repair Figure 1.

Get the motherboard, first test the LDO VCC of the interface chip CD3215 withou Short circuit, and VCC is normal.

Apple MacBook Pro a1706 notebook is not powered on for repair Figure 2.

CB304 has no VCC output at this time. Check SMC according to the time sequence to get SMC_RESET_L signal, then U1900 CLK will shake, and SMC’s own reading program will start pin configuration. All these are normal. Only the communication between SMC and CD3215 is found to be I2C bus, and one of them is abnormal. I2C_UPC_X_SDA2 can transmit normally.

Apple MacBook Pro a1706 notebook is not powered on for repair Figure 3.

I2C_UPC_X_SCL2 is abnormal,VCC rises to 3.3V instantly and then falls off.

Apple MacBook Pro a1706 notebook is not powered on for repair Figure 4.
I2C_UPC_X_SCL2 and EC communication have a resistor R3042 disconnected, and then measured by oscilloscope to find that the sending end of EC signal is normal, and then look at the disconnected waveform.

Apple MacBook Pro a1706 notebook is not powered on for repair Figure 5.

Test chart of main board.

Apple MacBook Pro a1706 notebook is not powered on for repair Figure6.

The problem is obvious, first remove a 3215 and then test the waveform.

If U3200 is removed, the fault is still the same. After U3100 is removed, the waveform will return to normal, and two of them will be replaced directly.