Analysis: If there is no WiFi, first measure the voltage at C5202_RF; it should be 3.8V. If not, connect a wire from another point to C5202_RF, then measure C5204_RF for 1.8V. If that is also absent, short R5208_RF, check and replace L5201_RF, and replace the WiFi module at C5202_RF!
If the WiFi signal is weak, check if the antenna is properly connected! Replace FL5201_RF and the WiFi module!
Mobile Repair Tips (Part Four)
1. Re-soldering Method: During use, frequent pressing of keys, flipping the cover, or dropping the phone can lead to cold solder joints or poor connections causing various faults. Use a magnifying glass to observe or apply pressure to identify the faulty area and re-solder to resolve the issue.
2. Wire Connection Method: When a phone is dropped or when disassembling a chip with adhesive, it is common for pads to come off. For useful pads that have come off, use a wire to connect them. Typically, connect fine enameled wire to the leads or components at the point of connection, then bend the exposed wire end into a circle the size of a solder point at the pad, secure it with green oil, and bake it under a UV light (commonly used UV light for currency verification) for about 30 minutes. Broken lines outside the chip can also be repaired using the wire connection method.
3. Antenna Method: Simple and practical, when troubleshooting RF circuit faults, use a wire or solder wire about 10 cm long, tweezers, or an oscilloscope probe as a dummy antenna, connecting it to the input and output of the signal path. If the phone works normally when the dummy antenna is connected to the input of a certain component, it indicates that the circuit after this component is normal. Then move the dummy antenna to the output of this component; if it does not work normally, the problem lies with this component.
4. Adjustment Method: If the transmission signal is too strong causing shutdown, or too weak causing reset or redialing, and repairing or replacing the power amplifier or power control circuit does not help, adjust the component values in the related circuit to achieve repair. For example, in Motorola V998 and Nokia phones, if the transmission power is too high causing shutdown, increasing the resistance in the power control circuit can solve the issue; if the transmission power is low causing redialing, reducing the base supply resistance of the preamplifier and increasing the gain of the preamplifier can make the phone work normally.
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Further Reading:
No Service | Phone SIM Card Jumping | iPhone 6 Case Study Three | iPhone 6 Case Study Four |iPhone 6 Case Study Five | iPhone 7 Case Study Six | iPhone 7 Case Study Seven | iPhone 7 Case Study Eight|iPhone 7 Case Study Nine| iPhone6 Case Study Ten | iPhone 6 Case Study Ten One|iPhone 6 Case Study Twelve|iPhone 6 Case Study Thirteen|iPhone 6 Case Study Fourteen|iPhone 6 Case Study Fifteen|iPhone 6 Case Study Sixteen|iPhone 6 Case Study Seventeen|iPhone 7 Case Study Eighteen|iPhone 6 Case Study Nineteen|iPhone 6 Case Study Twenty|iPhone 6 Case Study Twenty-One|iPhone 7 Case Study Twenty-Two|iPhone 6 Case Study Twenty-Three|iPhone 6P Case Study Twenty-Four|iPhone 6s Case Study Twenty-Five|Repair Lion Matters
