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This lesson is about the maintenance of plugged in charger with charging icon but no charging current

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You can know the charging current by observing the charger with charging current display,

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or the USB current detector

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This device is convenient for us to observe the magnitude of the charging current

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This is a charger with a charging current display

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This is a USB current detector

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It plugs into the charger on one end and the phone on the other

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Through this display, you can see the charging current and charging voltage of the mobile phone

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Next, look at the maintenance steps

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If there is a charging icon but no charging current when plugged in, how should we repair it?

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The first step is to rule out the problem of the charger and charging cable

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Directly replace the charger and charging cable to quickly eliminate

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If the charging current is normal after replacement,

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it means that the charging abnormality is caused by damage to the charger or charging cable

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If the charging current is still abnormal after replacement,

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you need to go to the second step

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The second step is to measure whether the battery is under-voltage protected,

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that is, whether the battery voltage is too low, or whether the battery has no voltage output

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Use the DC voltage range of the multimeter to measure

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If the measured voltage is relatively low,

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you can use the DC power supply to adjust the voltage of about 3.7 volts to 4 volts, and charge the battery directly

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Charge until the battery voltage reaches above 3.6 volts, stop charging

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Then install the battery on the motherboard battery holder for charging

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If the charging is normal at this time, it means that the fault is caused by the battery undervoltage

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If the measured battery voltage is normal, you need to go to the third step

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The third step is to eliminate the problem of the tail plug board and the tail plug cable

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The fastest way is to directly replace the tail plug cable or the tail plug board

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You can also use the tail plug cable and tail plug board of the same model to replace the test

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Plug in the charger after replacement

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The charging current is normal,

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indicating that the fault is caused by the damage of the tail plug board and the tail plug cable

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When charging, observe its charging current

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The charging current can reach more than 1 ampere, indicating that the charging current is normal

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If there is still no charging current after replacing the tail plug board and tail plug cable,

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you need to go to the fourth step

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The fourth step is to measure whether the voltage of about 4 volts of the main power supply is normal

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First, install the tail plug and connect the cable on the main board of the mobile phone

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One end of the charging cable is connected to the charger,

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and the other end is connected to the mobile phone

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Find the measurement position of the main power supply on the motherboard according to the circuit diagram

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Multimeter adjusted to DC voltage

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If no voltage is detected, it is generally a problem with the charging chip,

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just replace the charging chip

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If you can measure a voltage of about 4 volts, you need to go to the fifth step

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The fifth step is to measure whether there is voltage at the positive pole of the battery

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First, install the tail plug on the main board of the mobile phone and connect the cable

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One end of the charging cable is connected to the charger,

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and the other end is connected to the mobile phone

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Disconnect the battery connection cable, that is, do not let the battery connect to the motherboard

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Find the positive pole of the battery on the battery holder according to the drawing,

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and measure whether the battery holder has a voltage above 3 volts

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If there is no voltage, just replace the charging chip

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If there is voltage, you need to go to the sixth step

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The sixth step is to change the charging chip

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If the pad pins are not dropped, you can directly replace the charging chip,

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and generally the fault can be repaired

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That's all for this lesson