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Usage of multimeter

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In this video, we mainly explain how to use a multimeter to judge whether the line is on or off

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mainboard chips are connected together through board layers

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If the mobile phone is dropped, the circuit on the board layer will be disconnected,

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which will cause the machine to fail to boot

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We can use a multimeter to measure the connection of the circuit to troubleshoot the problem

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Method of measuring circuit connection with multimeter

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Step 1, insert the black marker of the multimeter into the common port,

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and insert the red marker into the red jack marked by the voltage resistance

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Step 2, the multimeter is adjusted to the buzzer range

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Step 3, the mainboard needs to be powered off during the measurement,

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and the circuit cannot be tested with power on

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Step 4, find the line connection point according to the bitmap

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For example, in the bitmap of the iPhone 12,

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we click on any red point, if other positions also turn into the same yellow color,

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it means that the yellow points are connected

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At this time, we can use the buzzer of the multimeter to measure the connection of the line

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Step 5, measure the two ends of the line with markers,

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or measure the components connected at both ends of the line

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Step 6, if the measured value is 0 and a buzzer sounds,

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it means that the line is connected and it is normal

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If the screen displays OL or 1 during measurement,

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it means that the line is disconnected,

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and we have to add a wire to connect the line

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Precautions when measuring connection

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The markers do not need to be distinguished when measuring

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A fine-needle test marker is required for measurement

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Because the components on the mainboard of the mobile phone are relatively small

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If a thick test marker is used to measure,

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it will lead to misjudgment or damage to the measurement components

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When measuring the connection of the circuit,

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the mainboard needs to be powered off before it can be measured

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When the power is turned on for measurement, the mainboard will be burned

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Let me demonstrate how to measure line connection

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Insert the black marker into the COM port,

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insert the red marker into the V red mark,

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and switch the multimeter to the buzzer range

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Take the iPhone 12 model as an example to find the measurement point

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In the bitmap, we click on any red solder point

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The yellow solder points in the bitmap are directly connected by wires

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One marker touches the upper yellow dot,

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and the other marker touches the lower yellow dot

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According to the position of the yellow dot in the bitmap,

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the red marker is connected to the yellow point above the power supply,

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and the black marker is connected to the capacitor position below the power supply

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At this time, we can see that the value shows 000,

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and the multimeter beeps, which means that the line is connected

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If the multimeter displays OL during measurement,

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it means that the line is broken

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we need to use a wire to connect the upper capacitor and the lower capacitor

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Ok, that's all for this video