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

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As we mentioned earlier, when the power button cannot be measured 1.8 volts,

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we can measure whether the 4 volts of the main power supply is normal,

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and we don't need to check the circuit diagram

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If the 4 volts can be measured around the power supply,

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it means the main power supply is normal

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If we can't measure the 4 volts,

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it means the main power supply is abnormal

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Let's take a look at where the main power supply is generally measured, and its voltage

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The voltage of the main power supply is equal to the voltage of the battery,

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if the battery voltage is 4.3 volts, it is 4.3 volts

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If the battery is low, only 3.8, 3.9, or 4 volts,

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we can measure 4 volts

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So where do we measure?

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When we get a mainboard,

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we can compare the bitmap or position map to measure

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Generally, we measure these capacitors around the main power supply,

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which is called blind measurement

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When we don't check the picture,

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we can measure the capacitors around it

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Generally, when measuring relatively large capacitors,

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we use the voltage gear

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If there is a voltage of 4 volts,

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but the power button has no voltage, what should we do at this time?

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We basically have to replace the power chip

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Ok, let's take a look at the conversion principle of the main power supply

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This is the common conversion principle of the main power supply,

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that is to say, how does the main power supply come from

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First, the positive pole of the battery supplies power to the charging chip

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The charging chip gets this power supply of about 4 volts,

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and its internal MOS tube will be turned on

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After it is turned on, it is directly converted into the main power supply, VPH_PWR

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This power supply outputs a voltage,

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which is equal to the battery voltage,

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and is given to the power chip

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This is the general conversion principle of the main power supply

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Let's take a look at Oppo phone's main power supply conversion principle

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Oppo mobile phones are special

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First of all, here is the positive electrode of the battery,

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which is turned on through a MOS tube, and then goes here directly

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First convert it into a battery reset power supply

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It's called VBT_RST, which is actually the positive pole of the battery,

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but the name has changed

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After the MOS tube, it arrives here and gives it to the charging chip

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The MOS tube inside the charging chip is turned on,

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the positive electrode of the battery is converted into the main power supply,

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and then supplied to the power supply chip

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The main power supply voltage equals to the battery voltage

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After we learn the conversion principle of the main power supply,   

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When the main power supply is abnormal,

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we know how to consider the problem

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when we measure that the main power supply is 4 volts,

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but there is no 1.8 volts on the power button,

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what should we do at this time?

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We generally re-solder the power chip, or replace the power chip

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Okay, that's it for this lesson