Troubleshoot: iPhone X Failed to charge ( fix PCB board)

Here is an iPhone X failed to charge, after replacing the iPhone battery, the iPhone X is still not charging, so we suspect it's the problem of the iPhone X PCB board, we need to troubleshoot it.

Before we are going to fix it, some phone fix tools are recommended:

- WUXINJI Dongle

- Phone opening tools

- Digital multimeter

- iPhone X PCB holder fixture

- Microscope

- Quick 861DW hot air rework station

- Tweezers

- other tools

Now, let's start to repair.

Open the WUXINJI Dongle to check iPhone X schematic diagram.

The charge principle of the iPhone XS is as follows:

According to the iPhone schematic diagram, after plug the iPhone data cable, the 47 48 pin of the iPhone tail plug connector J6400 will get 5V input voltage PP_VBUS1_E75, meanwhile, 20th pin HYDRA_C0N_DETECT_CONN_L will be pull down. U3300 passes through R3360 and then output PP_VBUS1_E75_RVP send to U6300. HYDRA_CON_DETECT_L send to G3 pin of the multifunctional electronic switch tube U6300, when U6300 received a low power signal, then it can be used to identify the connection of the iPhone charging cable.

When U6300 get the 5V power supply, and it has detected the connection of the iPhone tail plug, it will pass through UART data interface and feedback the information to CPU(U1000), after the iPhone charge IC U3300 received 5V, it also will pass through R3332,and feedback the information of external 5V to CPU. At this time, the iPhone battery icon turns green on the iPhone display screen, and then the iPhone lightning mark appears.

When the iPhone needs to be charged, U6300 will send start signal to HYDRA_TO_TIGTIS_VBUS1_VALID_L to U3300, and then the U330 starts to work, the iPhone X starts charging.

Use phone opening tools to disassemble the iPhone X, carefully take out the iPhone X motherboard. Attach iPhone X motherboard to the PCB holder fixture, and then measuring the detection signal HYDRA_COM_DETECT_L from the interface to the U6300, we found it's normal. Measure 5V PP_VBUS1_E75 voltage by digital multimeter, it only has 4.5V, which is abnormal. The 5V all can't be detected on U3300 and U6300, so the iPhone X is not charging. Measuring the diode data of 5V, it's more than 1600, which is abnormal too.

First we thought it was the chip connected to this circuit that pulled down the voltage, there was only one U330 on this circuit, so we replaced the U3300 directly, but the voltage was still abnormal.

Put iPhone under the Stereo Zoom Microscope, and then replace the circuit components connected to PP_VBUS1_E75RVP that was converted by U3300, they were U6200, DZ5900 and U300, but the problem still there, it still only 4.5V.

Now, we need to measure the peripheral circuit of the connected chip, when measuring the U3300 TIGRIS_LDO, it is short-circuited, and this voltage is only connected to 2 capacitors.

This voltage is the linear voltage used by the power supply chip, use QUICK 861DW hot air air rework station and Titanium Alloy Tweezers to replace the capacitor, and then measure it again, now the data tested is normal.

Assemble the iPhone X, and charge it, now the iPhone X is charging properly. Get into IOS to test other functions, all functions tested are normal.