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In this lesson we talk about how to repair no trigger faults

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According to the working process of the circuit,

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firstly, the positive power of the battery must be normal,

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and then when there is no problem with the charging chip,

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the main power supply can go to the power supply chip,

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and then the power supply can supply a 1.8V voltage to the power-on signal line,

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that is to say,

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the line from the power button circuit to the power supply should be normal

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In detail, there are 5 parts

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The positive circuit of the battery,

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the charging chip,

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the circuit of converting the main power supply,

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the power chip, and the power button circuit

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Ok, let's see how to repair

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We first observe whether the mainboard is corroded by water

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What about this water ingress corrosion

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We mainly look at the position of the power chip,

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and their circuits to see if it is corroded by water

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There is also the charging chip and its wiring,

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to see if it is corroded by water

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We focus on these

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If there is water ingress corrosion,

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we will deal with the corrosion first

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Dispose the corrosion and then power it up to see if it can be triggered

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If there is no water ingress corrosion,

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then what should we consider?

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We have to measure the voltage of the power button

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We should note that the voltage of Oppo's power button

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is equal to the battery voltage, about 4 volts

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Then Xiaomi and Huawei's power button voltage is 1.8 volts

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Use the voltage range of the multimeter to measure

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whether the voltage on the power button is normal

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The normal voltage of the power button is more than 1.7 volts

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This is basically no problem

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This is 1.8 volts, the error about 0.1 volts is no problem

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Ok, this is the boot voltage of 1.8 volts

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We are going to test to see if there is any problem

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Let's take a look

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The power button signal has different brands,

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and their pin definitions are different

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This is a Xiaomi phone,

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the power button signal of Xiaomi phone is called PW_ON,

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PW is the power

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It's called PHONE_ON_N here

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The voltage on the power-on button signal is actually

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added to the power-on line by the power supply

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Its English is this, which is always used by Xiaomi mobile phones,

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and the voltage on it is 1.8 volts

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So what about Huawei's power button? Let's take a look

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It is a voltage of 1.8 volts output by the power chip,

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which is a power supply, VOUT_PMUD

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Output this voltage to a 100K resistor,

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then the other end of the resistor is the signal end,

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we call it PWR_ON_N

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Then this end will go through the pull-up resistor, and there is a 1.8 volts

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Then the 1.8 volts voltage passes through this two-ohm resistor

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The power button holder also has a 1.8 volts

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This is the power-on signal

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This resistor cannot be short-circuited

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But for this resistor,

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we can generally choose 100K, 200K, both can be used

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When this resistor is falsely welded,

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there will be voltage on the left and no voltage on the right

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If there is no voltage on the right, then there is no voltage here

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There is no voltage here,

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we press the power button and there will be no response

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So this voltage is very important

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Let's take a look at the principle of Oppo 's power button signal

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The first is the battery

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The positive pole of the battery outputs a voltage of about 4 volts,

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The output voltage is given to this pull-up resistor, R2802

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This is one of the models we used as an example,

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and the location numbers of different models are different

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The resistor gets the voltage,

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then there is a voltage of about 4 volts on the power button signal

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This power button signal is called KYPD_PWR_N

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There is about 4 volts here, and it is about 4 volts here

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This is the same line

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There are about 4 volts here

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The power button also has 4 volts

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Here, ANT means antenna shrapnel

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Its power button is in the form of a shrapnel,

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not a boot room seat, not that kind of connector

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Here's how it works

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Its working principle is that when the battery voltage is normal,

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after the pull-up resistor, there is only a voltage here

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The voltage here is equal to the voltage of the positive electrode of the battery

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After there is a voltage of 4 volts,

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here and here are the same line,

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then there is a 4 volts at one end,

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after a 1K resistor, there will be a 4 volts at this end

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This is the power button signal of Oppo

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Okay, that's it for this lesson