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In this lesson, we talk about the channel of the handset signal in the circuit diagram

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We talked about HiSilicon and MTK models earlier, and their circuits are driven by scmall audio

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They are modern mobile phones that support dual speakers

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Their drive circuit structures are almost exactly the same,

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maybe only the type of chip that drives the earpiece is different

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Here we are talking about an early model of Qualcomm

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Because Qualcomm's modern models are no different from those of HiSilicon and MediaTek

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Let's talk about a low-end model

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It is different from these two circuits

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Let's take Changxiang 9 as an example, it is Qualcomm's early mobile phone

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We can start from ANT1701 to find

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Open Xinzhizao, find the Huawei Enjoy series, and open its circuit diagram

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In the circuit, if you want to find its earpiece circuit, how should you find it?

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We still use the safest way, first enter the RCV to see if we can find it

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Nothing was found

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Then type EAR, we found EAR

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CDC_EAR_P and CDC_EAR_M are earpiece signals

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The earpiece signal comes from the chip U201F

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The chip U201 is divided into six parts: ABCDEF

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This is the sixth part, which is about big audio

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We have seen the microphone, we have seen the SPK, we have seen the EAR,

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and we can basically confirm that this part describes the big audio

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Here is also the signal of the headphones

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Its earphones are called HPH or HS

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Next we need to find the earpiece

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The earpiece signal is the output sound signal from pins 93 and 94 of U201,

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CDC_EAR_P, CDC_EAR_M

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Let's double click on one of them to see where it goes

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It's here, keep going here, the name becomes CDC_EAR_P_CON, CON refers to the connector

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It has shrapnel ANT 1701 and ANT 1702

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The shrapnel goes into contact with the earpiece, making the earpiece emit sound

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This is the earpiece circuit of an early mobile phone that does not support dual speakers

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The resistors in series in the circuit, such as R1701 and R1702

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If they are corroded by water, you can measure infinity from this end to the ground

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We must first consider whether the two inductors are falsely welded or damaged,

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and they can be directly shorted to solve the problem

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The component D1701 is anti-static

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Anti-static components will also cause the signal of this line to be pulled down,

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resulting in abnormal sound from the earpiece, or no sound from the earpiece

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How to solve this time?

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You can remove this D1701 without installing it

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It is only anti-static protection, the circuit can work normally without it

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It should be noted here that components like this one end connected to the line

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and the other end grounded are more important in this sound circuit

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For example, capacitors C1701 and C1702, if there is no water corrosion,

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usually do not care about them, generally they will not be damaged

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The earphones are on the Android phone, and the common codes of the earphones are: HPH, HS

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For example, HSDET is the insertion detection signal of the earphone

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If there is a problem with this signal, it will enter the headphone mode

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In the headphone mode, only the music can be heard in the settings,

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and there is no sound in other cases, and the recording is not normal

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That depends on where the headphone insertion detection signal goes?

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Is it leading to the tail plug board or the tail plug cable?

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It also depends on whether there is a problem with this chip,

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which leads to a misjudgment of the headphone detection and automatically enters the headphone mode

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Then the above HPH_L, HPH_R

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They are the output signals of the speaker above the earphone

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One left channel, one right channel

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This is the speaker signal for the right channel, and this is the speaker signal for the left channel

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In this drawing, two code names are used to refer to the earphones at the same time

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This is an early earpiece, its circuit is driven by big audio

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This part mainly describes its big audio

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Let's sum it up

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CODEC or CDC means big audio, also called main audio

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The small audio is called SMARTPA,

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and the earpiece is called RCV, EAR or SPKR

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Speaker is SPK; Microphone is MIC

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That's all for this lesson