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This lesson talks about the maintenance for no baseband fault of Android phones

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Mainly from the following five aspects

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First, the failure phenomenon of no baseband

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Second, the general overview of the baseband circuit

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Third, the working principle of the independent baseband circuit

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Fourth, independent baseband fault maintenance

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Fifth, CPU integrated baseband fault repair

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First look at the failure phenomenon of the Android mobile baseband failure

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The following figure shows common baseband faults of Android phones

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In the settings, the display of IMEI or MEID on this machine is unknown,

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which means there is no baseband fault

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That is, the baseband circuit of the mobile phone does not work, usually called no baseband

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The other mobile phone is the same, and the serial number i m e i is displayed behind unknown

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This is a malfunction without baseband

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Next, let's take a look at the baseband circuit of the Android phone

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The baseband is integrated in the CPU,

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that is, the baseband CPU and the large CPU are not separated, and most Android phones are like this

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Its baseband circuit is also the circuit of the CPU

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Generally, the mobile phone can boot into the system normally,

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and it has nothing to do with no baseband and a large CPU.

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With the beginning of the 5G era, individual models of Android phones have separate baseband CPUs

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The baseband CPU has its own independent circuit, which we call the baseband circuit

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It has an independent power-on circuit, and the power supply is generally more than 10 channels

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It also has a clock signal, which is divided into a sleep clock and a main clock, which are generally output by a separate clock chip

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It also has a reset signal, usually issued by the baseband power supply

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The maintenance signal sent by the baseband CPU to the baseband power supply, PS_HOLD

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The baseband CPU transmits the demodulated pictures and videos to the CPU through the PCIE bus

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Another bus is Qlink bus, USRDL or UL

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DL is downlink, UL is uplink, they together constitute the Qlink bus

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It communicates with the radio frequency transceiver

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If this bus fails, it will result in no baseband

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This is Android mobile phone baseband failure phenomenon and baseband circuit overview

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That's all for this lesson