In the previous issues, ORIWHIZ summarized some common mobile phone repair methods for the reference of some new mobile phone repairers and engineers. Today we continue to bring you more and more detailed repair methods. If you need to purchase the maintenance tools required by the corresponding method, please visit our website ORIWHIZ.COM for purchase.

Mobile phone repair method

Comparison method: When repairing mobile phones, when the model, position, voltage value, current value, and waveform of some components are considered abnormal, the corresponding parts of the normal board of the same model can be used for comparison. For example, the position of the double triode, whether a certain resistance, a capacitor is installed wrongly, whether the resistance value is normal, whether a certain two points are connected, etc., the fault can be found quickly through comparison.

Substitution method: When it is suspected that there is a problem with a certain component, the same component can be removed from the normal mobile phone for installation experiment, and the effect is immediate. If the fault is eliminated after the replacement, it means that the original component has been damaged. If the fault still exists after the replacement, it means that the problem is not in this component and should continue to search. The substitution method applies to all components in the mobile phone. Under certain circumstances, single-frequency components can be used to replace dual-frequency components. For example, 14 series single-frequency power amplifiers are commonly used to replace Hitachi’s dual-frequency power amplifiers, but they can only be used in areas where only the GSM frequency band is available.

Temperature sensing method: often used for small current leakage or large current caused by component breakdown. If the mobile phone is powered on, there will be tens of milliamps of leakage. Although it does not affect the use, the battery standby time is greatly shortened. During maintenance, the power supply voltage can be increased to increase the leakage current. Find the heating element, which element heats up is damaged; you can also smoke the circuit board with loose cigarettes to coat a layer of white mist on the element, and observe after powering up, which element the fog layer disappears first, that is, it is a heating element; such as powering on a mobile phone That is, there is a large current of 500 mA or more, and the power supply voltage can be adjusted to lower the power supply voltage so that the current does not exceed 200 mA (without expanding the fault). After power on, use the above method to find the heating element and replace it.

Short circuit method: It is often used for emergency repairs when some components are missing, such as antenna switches, filters before and after high amplifiers, combiners, power amplifiers and other components are damaged. After the antenna switch is short-circuited, the mobile phone can only work in one frequency band). If the mobile phone returns to normal after the short-circuit, it means that the component is damaged.

Pressing method: used for various faults caused by poor contact or virtual soldering of components. If the phone does not turn on when the phone is turned on, and you suspect that the font or CPU is soldered, you can use your thumb and index finger to press the two sides of the chip appropriately. If you press a chip, it can be turned on.

Suspended method: It is mainly used to check whether the power supply circuit of the mobile phone is disconnected. It is simple, practical, convenient, and fast. The method is: the positive terminal of the repair power supply is connected to the ground terminal (negative terminal) of the mobile phone, the negative terminal of the repair power supply and the positive terminal of the mobile phone aisnot used, and the positive terminal of the power supply is added to all circuits that can pass DC. At this time, use an oscilloscope (or a multimeter, the ground is connected to the ground of the maintenance power supply) to measure the part you suspect of an open circuit, if there is a voltage, it means there is no open circuit; if no voltage is measured, it is an open circuit (or empty point).

Open circuit method: It is to disconnect the suspected circuit or component. If the fault disappears after the disconnection, it means that the problem lies in the disconnected circuit. For example, when a large current is applied, the power amplifier is directly powered by the power supply, and the inductance or resistance of the power supply branch can be removed, and the large current no longer appears, indicating that the power amplifier has been broken down and damaged; if the SIM card is not installed, the mobile phone has a signal, and there is no signal after the card is installed. Signal, if there is a problem with the power amplifier, you can also disconnect the power supply of the power amplifier or the input path of the power amplifier. If there is a signal, it proves that the power amplifier is damaged.

Waveform method: When the mobile phone is working normally, the signal waveforms of the circuit in different working states are also different. When troubleshooting, use an oscilloscope to measure whether the signal waveform is normal, and you can quickly determine where the fault occurred. For example, when there is no signal in the maintenance, first test whether there is a normal receiving baseband signal to determine whether it is the radio frequency circuit or the logic circuit. It can also measure whether there is a normal transmitting baseband signal to determine whether the fault is caused by a logic circuit or a radio frequency circuit.

Oriwhiz (Shenzhen DongYe Tengfei Electronics Co., Ltd) is a professional iPhone, iPad, iMac, Mac Book, Xiaomi, Huawei, Samsung, Sony, LG, ASUS repair parts and repair tools supplier. Oriwhiz team aims to provide the best quality cellphone replacement parts and repair tools to all customers. We provide comprehensive solutions for cellphone, digital devices, computer repair shops with powerful and handy cellphone repair packages, repair tools, and repair machines. Browse our product category to select an item you like or contact us for wholesale and distribution issues.