Xiaoxin PRo13 is not powered on for maintenance

Xiaoxin PRo13 is not powered on for maintenance.

Model: Xiaoxin PRO13

Fault: No power supply.

Overhaul process: the colleague next door sent Xiaoxin PRO13 2020 for repair, saying that it could not be turned on and needed urgent treatment. Visually, the appearance of the machine is undamaged and very clean. Plug in the adjustable power supply, the current is 0.00, and there is no response when starting.

When disassembled the whole board, there was no scorching of the feed liquid, and there was no obvious abnormality in measuring the resistance values of the major inductors. Power-on measurement of four pins of TYPEC interface (non-)blueprintFour pins, the fourth pin of the exposed pin of the interface) only have a voltage of 5V, which is normally 20V. It seems that there is no boost. The previous contact PJ39 actually has 9.2V What is the situation?

Re-test U38 input ADIN_1 has a stable voltage of 5V. The control USB_C1_VBUS_EN voltage with an output of 0.U38 is converted from +3V3_IN_PD and USB_C1_VBUS_PD_EN of the pull-up resistor R650. The measured voltage of the two pins of R650 is 0, and the two pins of Q28 are sent by U32 TPS65988 USB Type-C and the power transmission (PD) controller 48.

Check that pin +3V3_IN_PD of chip power supply pin 5 is 0v, and+3v3 _ in _ PD is renamed from +3VALW through R652, and there is no voltage at one pin of R652. +3Valve is generated by PU21(TPS5139P), and it hasn’t been boosted yet. It’s strange that it came to the standby side. The VIN of PU21 has a voltage of 9.2V, and the 12-pin EN has no voltage. The EN voltage comes from +3.3VLDO through PR142 and PR145, and there is no voltage at each end of the two resistors. +3.3VLDO is issued by pin 15 of the chip itself, and the resistance of the measuring pin is normal. Replace TPS51393 directly. After cooling, the next power-on has automatically triggered code running. After measuring PJ39, it is still 9.2V, and the voltage at the four pins of TYPEC interface is 20V. Pick up the screen and light up the machine.

Concluded that this machine was caused by the damage of 3V power supply chip 51393. TYPE-C control chip TPS65988 external program is unknown on the board, and it communicates with EC through I2C bus. There are microcode programs downloaded in official website and upgraded under the system. Due to time, it was not possible to measure where VBUS_OUT_P1 and VBUS_OUT_P2 went.