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This lesson is about maintenance for the prompt of abnormal temperature

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Let's first look at the fault phenomenon abnormal temperature prompt

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When the charger is plugged in, it prompts that the temperature of the mobile phone is too low and the charging stops

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In another case, after plugging in the charger, a triangle and an exclamation mark appear

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These are all abnormal temperature failure phenomena.

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Let's take a look at the circuit related to abnormal temperature

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In the mobile phone circuit, the circuit with abnormal temperature is connected from the battery to the battery holder

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It has a signal dedicated to temperature detection, TEMP or TS

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This temperature detection signal is connected from the battery to the battery holder,

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and then from the battery holder to the charging chip or power chip

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Next, let's take a look at Huawei's temperature detection circuit

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The temperature detection circuit of Huawei mobile phones is also connected

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from the battery to the battery holder,

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and then connected to the main power supply

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There is a pull-up circuit in this line, and there is a signal channel

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This signal line is from the battery to the large power supply after passing through a 1k ohm resistor

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This is its concatenated channel

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The pull-up circuit mainly gives this signal line a voltage of 1.8 volts

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The resistance is normal, the voltage of the power supply terminal is normal,

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and the voltage of 1.8 volts on the signal line will be normal

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The order in which it works is, first there is this 1.8 volt voltage

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This resistor is normal, and its detection line can maintain a voltage of 1.8 volts here

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After there is a voltage of 1.8 volts, the right end of the resistor R1501 has a level of 1.8 volts

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In this way,

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the large power supply can detect the temperature information of the battery through this signal line

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If the voltage of 1.8 volts cannot be measured here,

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then it is necessary to test whether the circuit on the left side of resistor R1501 has a voltage of 1.8 volts

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If there is 1.8 volts on the left end of the resistor but not on the right end,

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the R1501 resistor is usually damaged, just replace it

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If there is no 1.8 volt voltage at the left end of resistor R1501,

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we need to consider whether the pull-up resistor is abnormal,

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and whether the power supply at this end is normal

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If there is 1.8 volts at the power supply end but not 1.8 volts at the lower end of the resistor,

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it is usually caused by a problem with the resistor, and you only need to replace the resistor

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If the lower end of the resistor does not have 1.8 volts,

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repair the upper end of the power supply

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There is no 1.8 volt voltage here, and the power supply needs to be repaired at this time

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To see which chip the power comes from, you need to repair the chip that provides the power

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In maintenance, if the value of the battery temperature detection line to ground is infinite,

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it is only necessary to consider whether the resistor R1501 is falsely soldered or not

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If re-soldering the resistor still doesn't work, then consider replacing the resistor

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This is Huawei's temperature detection circuit

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That's all for this lesson