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In the step 3 of short sircuit repairing for iPhone standby circuit

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If we find that only the charging tube, charging chip,

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or boost chip is hot,

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and no hot components are found in other positions,

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we will use step 4 to repair

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The maintenance process of step 4: Distinguish the fault point

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We first measure the diode values of the battery connector's positive pole,

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the main power supply and the boost power supply

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The normal value is around 300

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If the diode value is 0, the power supply is short-circuited

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For example, when we measure the main power supply,

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the diode value is 0,

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which means that the main power supply line is short-circuited

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How do we do after measuring the short circuit?

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According to the bitmap,

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smoke the components connected by the short circuit with rosin,

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And then opearte the burning detection

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Tips for smoking rosin,

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if the short circuit components are inside the shield,

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we can smoke the outside first.

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When no fault is found, we will smoke the inside of the shield and then deal with it

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Next, let me demonstrate how to measure the battery positive pole,

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the main power supply and the boost power supply

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Let's take the iphone 7 Qualcomm mainboard as an example

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We first find the battery connector on the component map,

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and then find the position of the battery connector on bitmap

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After distinguishing the positive pole,

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we can measure the diode value of it

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What about the main power supply? Let's take a look

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We search for the signal PP_VDD_MAIN in the bitmap,

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and any yellow point in the map can be measured

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We will measure the position of C2611 or C2612

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If you want to find the BOOST power supply,

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you only need to search for the name PP_VDD_BOOST in the bitmap

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The yellow positions indicate the BOOST power supply components

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We find the corresponding components in the real object,

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and then measure its diode value

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Now, let's start to measure

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The multimeter is turned to the diode gear,

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the red test pen is grounded,

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that is, connected to the screw column or the SIM card slot,

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the black test pen measures the positive pole of the battery,

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and the value shows about 300, indicating that it is normal

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Let's go to measure the main power supply

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The red test pen is grounded,

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and the black test pen is connected to the main power supply measurement point

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The value is 0, indicates that the main power supply is short-circuited

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If the main power supply is normal, let's test the boost power supply

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The red test pen is grounded,

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and the black test pen is connected to the boost power supply measurement point

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The value is around 300, indicates that the boost power supply is normal

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If the value is 0, it means the boost power supply is short-circuited

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Through measurement, we found that the main power supply of this mainboard is short-circuited

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We smoke all the short-circuit power supply connection components with rosin

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Set the temperature of the soldering iron to 350 degrees when smoking rosin

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Dip the rosin with the tip of a soldering iron and smoke it on the components

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Move tip back and forth about 5mm away from the mainboard

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t is best to smoke rosin in a windless environment

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The positions where the main power supply is not connected does not need to smoke rosin

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Remember to clean the tip of the soldering iron after smoking the rosin

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We smoke the components connected to the short circuit with rosin,

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and the components inside the shield do not need to be dealt with

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If the measurement has no results,

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we will disassemble the shield and deal with it

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Next, let's go to the fifth step, burning detection