iPhone 12 Pro Max Repair Cases (Part II)

Let’s continue to introduce the iPhone 12 Pro Max repair cases

Case 4. Flash function failure

Receive the phone from the customer, then test the functions. After testing, the LED flash function failed. The flash button can be activated but the flash torch does not work.

Since all functions work well except the LED function with the problem.

So first, we can replace a LED flex cable to test, the issue remains the same with another new flash LED connected.

Then the issue should come from the motherboard LED circuits-related part. Referring to the schematic and motherboard components distribution, first, we lock the target at the LED flash driver IC (location number U6500).

Remove the chip as the red circle marked and replace it with a new one.

Then test again, the LED function is back to normal.

Case 5. iPhone 12 Pro Max Cannot Startup

Connect the motherboard with DC power supply machine to check, the current leakage was found on the PP_VDD_MAIN power relative rails.

The working principle of the iPhone 12 Pro Max should be more or less the same as iPhone 11 Pro. So we can refer to iPhone 11 pro theory course, find out the PP_VDD_MAIN related chips like the charging IC and small components around it to test first.

Separate the two lays of the motherboard, then remove the shielding cover on the charging IC and apply rosin. After that, connect with DC power to supply a 4 volts voltage. No short was found.

Then apply rosin on the surface of the second layer of the motherboard (signal board), then assemble the two layers of the motherboard with a test fixture.

Apply the 4 volts DC power again, the magic thing happened! The rosin on the surface of the C1900_E gets melted.

So the current short must come from the small capacitor.

Since it’s a filter-type capacitor on the PP_VDD_MAIN rail, so we can just remove it directly.

After that, assemble the phone and test again, phone can be booted normally, the issue gets fixed perfectly by capacitor replacement.