How to fix iPhone X charging problems

Fault Description: iPhone X happens something wrong on charging because of the tortuous repair process.

Possibility Reason: we doubt there happens something on 20-pin HYDRA-CON-DETECT-CONN-L.

Actually, usually the schematic problems, we will use the Wuxinji Dongle to check it, compared with normal value,  Insert the iPhone tail plug flex cable  and connect to J6400's 47, 48 pin, get 5V input voltage PP-VBUS1-E75. Then we will get the answers we want.

Picture 1

U3300 output PP--VBUS1-E75-RVP and sent to U6300 via R3360 again.

HYDRA-CON-DETECT-CONN-L changed the name to HYDRA-CON-DETECT-L via R6410.

Picture 2

HYDRA-CON-DETECT-L send the G3 pin to multi-function electronic switch U6300. When the U6300 receives a low level signal is also used to identify the link of iphone charging cable.

U6300 receives 5V power supply, and being tested that when tail plug being accessed, it will feeds the information back to the CPU (U1000) through the UART data interface. After receiving the 5V, the USB control chip U3300 IC  will also feed back the information of external 5V to the CPU through an R3332. Now, iphone's battery turns to green and the lightning bolt appears.

When need charging, the U6300 sends an turn on signal HRDRO-TO-TIGRIS-VBUS1-VALID-L to U3300, then the U3300 works and starts charging.

Picture 3

Now, we know the Schematic, next use Hantek Digital Oscilloscope  to measure U6300 signal HYDRA-CON-DETECT-CONN-L, we found it was normal. And use Fluke multimeter (VC712) to test 5V voltage PP-VBUS1-E75 is only 4.5V, we all felt surprise that the problem comes from this.  Detected abnormal 5V from U3300, U6300, so it can not be charged.

We thought it was a small problem before, guess the lowered resistance cause to the low voltage . However, after test, we found the 5V appears short circuit, but the secondary body value is normal about 1600.

Repair Thought : Since the voltage is reduced, the chip connected to this line must be pulled down. But there is just a U3300 on the line, so replace the U3300 and test the voltage again. Then change the Circuit component connected to the PP-VBUS1-E75-RVP that from the U3300, (U6200, DZ5900, U6300) is the same.

The original 5V voltage is still only 4.5V, we already have no patience，
put it aside. After one week, we take the motherboard and decided to repair again, check from the peripheral circuits of each connected chip, when test the TIGRIS-LDO on U3300, it is actually short-circuited. Its voltage is only connected to two capacitors.

Picture 4

This voltage is the linear voltage used by the power supply chip. Replace the Capacitance , charge and turn on, everything is normal.


Remark: The chip is linearly used for its own usage after get 5V main power supply. This circuit is also often found in notebook. Because the chip is usually a linear regulator module inside, the output short circuit usually pulls down the input voltage.