Huawei P8 Youth Edition Mobile 4G Single Board Q1602 Corruption Causes No Charging, No USB Recognition

I. Description of the phenomenon, problem

The fault on the maintenance work order for the phone does not charge, plug USB does not respond.

Second, the key process, root cause analysis

1. As the motherboard for the market repair, dismantling the motherboard before doing any maintenance actions, first consider whether the motherboard is burned out or customer plug and play Damaged USB interface phenomenon, that is, the first visual inspection of J1602 (USB interface) and the surrounding components appearance, found no abnormalities.

Considering that the phone does not have any response when plugged into the USB, the motherboard fault for not charging, do not identify the USB, it is likely that USB The interface has open pins or path open phenomenon. But the measurement of the USB interface of the various pins to ground impedance, and normal board comparison are normal.

3. Since the ground impedance is normal, the motherboard is no problem with the channel, but does not mean that the motherboard voltage and power supply are normal, so view the circuit diagram , through the circuit diagram USB interface pin by pin towards the measurement of each pin path voltage.

Huawei P8 Youth Edition Mobile 4G does not charge, does not identify USB repair Figure 1

4. The measurement process and corresponding measurement points are shown in the following table.

Huawei P8 Youth Edition Mobile 4G does not charge, does not recognize USB repair Figure 2

Visible measured voltage values are also normal, but considering the VBUS_USB to charge management chip (U201) between the Also through a field effect tube Q1602, this field effect tube is to control the VBUS_USB voltage to protect U201 So we measured the voltage of VCHG (C1622) and found that the voltage is 4.23V, which can be seen after Q1602. The voltage is reduced by 0.7V. Consider the voltage reduction of the control due to Q1602 body damage.

Conclusion, solution and effect

After replacing Q1602, the phone charges normally and identifies USB normally.

IV. Summary of experience, preventive measures and standard recommendations

The two faults of not charging and not recognizing the USB are often both present at the same time, and when fixing such faults be sure to link them together for a comprehensive repair. Location. The key point of such failure is about the USB pin measurement, step by step in accordance with the pin measurement anomaly, against the wiring diagram for Find out why.

Weak WiFi signal on iPhone 6P

Machine model: iPhone 6P

Fault phenomenon: weak WiFi signal, sometimes no WiFi

Failure analysis: rule out antenna problems, remove the chip to see if it is a virtual solder.

Repair process.

The signal is weak, remove the chip to find the 45 pin drop point, this point is just the 2G signal input of WIFI.

Repair point fly line.

Solder on the chip, installed test function all normal, fault repair!

iPhone 6p phone external no sound, headphones normal

Faulty model] iPhone 6p 64g

[Fault phenomenon]

Customer description said the phone external sound, insert headset normal, vibration and answer the phone are normal.

[Failure Analysis]

The boot test is indeed the same fault as described by the customer, because plugging in the headset normally represents the working condition of the phone big audio is already met. It could be a problem with the big audio chip and the audio amplifier or the I2S2 (the audio cable for the external amplifier). It could also be caused by the external pairing.

[Repair Process]

First troubleshoot the external match problem, the phone motherboard removed into our test machine rear shell assembly inside, boot test again found that the original fault. Now you can basically rule out the reasons for external distribution, the target directly aimed at the large audio IC disassembly chip, observe the pad with or without tin and drop point. All normal directly to the material board to remove a large audio IC tin mounted. And then this boot test found that the fault is still the same, now basically rule out the cause of the big audio IC. Disassemble the audio amplifier, measure the corresponding points, found 45_AP_TO_CODEC_XSP_I2S2_, and then remove the audio amplifier. BCLK (I2S2’s clock signal) is disconnected.

This point is only connected to the big audio, audio amplifier and CPU, dismantle the big audio to measure the corresponding point found resistance value is normal, directly from the big audio below to pull a first fly line to the audio amplifier to the corresponding point.

Directly mount the audio amplifier, power on the test.

Repair results]

Power on test, normal external playback, fault repair completed.