The customer brought an iPhone 6 to the Bgacenter service center, with a malfunction – the iPhone does not charge. Since the service center does not only carry out “complex” repairs of phones and tablets, but also conduct training on diagnostics and bga soldering; it was decided to perform this repair by the technician completing the soldering courses.
How was the board diagnosed:
Then we connected the phone to the laboratory power supply by disconnecting the battery.
The next step was to determine the current consumption by briefly pressing the power button. On a working telephone, the current consumption should be 0.08 A. In fact, the value of the LBP ammeter was 0.23 A. We conclude that the charge circuit is faulty.
The diagnosis indicates a malfunction of the chip U1700 (TRISTAR). In the diagram below, the U1700 is highlighted in red.
Then we disassembled the phone, and prepared the board for the replacement of TRISTAR.
Then we soldered the protective cover on the motherboard. Previously, we installed the radiator on the NAND Flash in order not to damage the chip “flooded” with the compound.
Then we measured the voltage on the capacitor C1704. The voltmeter showed the presence of a voltage of 4.3 V. in the serviceable charge circuit of the iPhone 6, on this capacitor, there should be 5 V. Reduced voltage confirms the malfunction of the u1700 chip.
Then we soldered the faulty chip, removed the remnants of the compound and prepared the contact area for the installation of a new chip, аfter making sure that the voltage in the charge circuit increased to 5 V. For this purpose, voltage measurements were carried out, with the Tristar chip removed.
Then we soldered a new (serviceable) U1700 chip, installing it by key.
Then, voltage measurements were performed on the capacitor C1704. The voltmeter showed 5 V. This indicates that a working microcircuit is installed and it works.
We collected the phone and connected it to a USB tester. The ammeter on the tester showed 1.65 A, which means the consumption is on.
Indications of the degree of charging the battery began to rise, the phone is charging.
Repair completed successfully.