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This lesson is about repairing the speaker without sound

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The first step, we first check whether the components related to the small audio are corroded or missing

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Of course, you can't just check the circuit of the small audio, but also check the cable that drives the speaker,

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and the socket on the mainboard that transmits the electrical signal to the speaker

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Pay attention to whether the cables on the mainboard have been corroded by water,

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and whether the small board of the tail plug has been corroded by water

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If there is serious water corrosion, it can be cleaned

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If there is a component missing, see what circuit it belongs to

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If the filter capacitor on the power supply is dropped, you can ignore it

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If there is serious corrosion,

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it is necessary to measure whether there is a short circuit in the line where it is located

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The second step, use the resistance file of the multimeter to measure the speaker

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Of course, this is a relatively comprehensive method,

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we do not measure the speaker in many cases

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It is normal for the resistance value of the resistor to be around 6-10 ohms

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For example, this speaker has a resistance of 6.4 ohms

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If the measured value is 0 or OL, it means that it is damaged,

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which means that there is a problem with the speaker

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Be careful, use the resistance file, not the diode file, they are not the same

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Step 3, if you check the appearance, you find no corrosion,

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no missing parts, the mainboard is clean, and it鈥檚 okay to use a multimeter to test the speaker

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At this time, it is necessary to measure the positive and negative ground value of the speaker signal

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Let's take Huawei P40 as an example

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First find the seat at the end of the speaker and measure this end

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The diagonally opposite corners are the positive and negative contact points of the speaker,

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so the test must be correct

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What is this measurement?

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It is to test whether there is any problem with the circuit of the small audio chip on the mainboard

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If there is a problem with the ground value, short circuit or open circuit,

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analyze according to what we have learned before

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If it is an open circuit, measure the components in series in the line

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If it is a short circuit, it is also to measure the components in the circuit

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The fourth step is to turn on the power and measure the large capacitance around the ringtone amplifier chip

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This large capacitor is usually on the main power supply line,

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and it generally has a voltage of about 4 volts

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The voltage of the mains supply is almost equal to the battery voltage

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The ringtone amplifier chip is a small audio

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The capacitor on the small audio side is relatively large, usually it is on the power supply line

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If there is a problem with the main power supply, it is more serious

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The phone turns on, but there is no sound from the speaker

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If the voltage cannot be measured on the main power supply,

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it is a broken line, and the flying line can be solved

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This is the most basic method

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Here we take a Huawei model as an example

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This is its little audio chip, this is a 1 microhenry inductor

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Its main power supply is on this capacitor

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Actually do not need to power on, because we measure the main power supply

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Step 5, turn on the phone and measure the medium-sized capacitance on the side of the ringtone amplifier chip

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Here because this is also a 1.8 volt power supply

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If this power supply has no voltage, we can deduce that the line is broken

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Why?

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The power supply of this 1.8 is often shared with the power supply of the CPU.

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If it is designed so that the power supply is independently output to supply power to the small audio,

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it is necessary to check why the voltage cannot be measured for this power supply,

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which chip it comes from, and focus on the chip that provides power to the small audio

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This lesson ends here