Malfunction Phenomenon
Received an iPhone 6s with boot issue from customer.
Try to press the power key button to power on, the phone cannot be booted and check the DC power supply with 50mA current leakage.
Troubleshooting Process
First, we should have some basic idea about the boot process main related chips and components.
Just similar as iPhone series, like iPhone 7 and iPhone X. The boot process related with below main chips and components.
· Battery Connector: J2400
· Charging IC: U2300
· Power switch connector: J4700
· PMU: U2000
· 32.768KHz Crystal: Y2200
· 24MHz Crystal: Y0600
· CPU: U0600
And the block diagram as below, for detailed and HD block diagram you can download the Refox bitmap to have a check.
Then the second step, let’s take apart the phone and run the cosmetic inspection of motherboard.
Since the issue is can not start up with 50mA current leakage, based on repair experience.
There is a high chance the issue is caused by the lines between PMU and CPU, like the power supply rails and I2C control rails etc.
After checking, we found the R0900 is missing, which is just located in the I2C bus lines.
Then resolder a resistor with the same specification and test, the phone can be booted normally.
Assmeble the phone and test again. All function works well, issue get resolved perfectly.
Summary
The serious issue may caused by little components, do not afraid of the tough nut!
You can also learn more from REWA academy, let’s make repair easier.
