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This lesson is about maintenance for the prompt of abnormal temperature

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Step one, find the battery holder

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First measure the ground value of the temperature foot of the battery holder

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The names of the temperature feet of different brands of mobile phones are different

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Generally, there are TEMP pins and TS pins,

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and some use I2C bus lines instead of temperature detection

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If it is measured that its ground value is abnormal,

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it is basically caused by the damage of the components connected in series

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from the battery holder to the charging chip,

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and generally needs to be re-soldered or replaced

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These components have resistors and composite MOS tubes

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If there is no abnormality in the ground value,

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go to the second step to check whether there are corroded parts around the charging chip and the power supply

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The second step is actually to check whether there is any abnormality in the appearance

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If the charging chip has obvious water corrosion, re-solder the chip directly

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After the replacement, start the test

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If there is no temperature abnormality and it can be charged normally, the fault will be repaired

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If it still doesn't work after re-soldering, generally the chip needs to be replaced

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If you see serious corrosion around the charging chip or power chip, and small components are lost,

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it is best to replace these small components first.

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The above is the second step

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If there is no water corrosion around the charging chip and the power supply,

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you can take a new battery and replace it for testing

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If the abnormality is eliminated, it means that the charging is abnormal caused by the battery failure,

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and the battery can be replaced directly

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After replacing the battery, if the fault still cannot be solved,

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the chip connected to the temperature detection pin should be replaced,

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usually the power chip or charging chip

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Sometimes, the abnormal temperature prompt is caused by an abnormality in the temperature detection circuit

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This circuit generally uses NTC thermistors to complete temperature detection

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Find the code THERM in the circuit, you can find the temperature detection pin

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Usually the chip responsible for temperature detection has a small power supply,

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and some are the main power supply

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What is the principle of temperature detection?

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This is the thermistor with a negative temperature coefficient

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When the temperature on the mainboard rises, the resistance value of the resistor will become smaller,

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and the signal on the signal line will change

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The power chip processes the amount of change and transmits it to the CPU

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When the CPU detects that the temperature of the area responsible for the thermistor is abnormal,

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it will prompt the mobile phone to display an abnormal temperature

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At this time, if the resistance is caused by water corrosion and damage,

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the resistance can be removed directly without installation

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If it is caused by the abnormal circuit around the thermistor,

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the abnormal circuit must be repaired to solve the fault

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This is the maintenance procedure for the prompt of abnormal temperature

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That's all for this lesson