Failure phenomenon There was no sound when the customer watched the movie normally, and the customer sent it to other repair shops for repair and replacement of the small audio, and the same was true for brushing the machine. The other components were not moved. Repair process The sound of watching a movie is sounded by the hands-free speaker, while watching a movie without sound is actually a hands-free fault. No hands-free is a kind of fault that is easier to repair, and related components generally include large audio chips and small audio chips. The customer sent a single board. After receiving the board, first install it in the test machine assembly and start the system for testing. It is found that except for the ringtone and hands-free, the receiver, sending and recording functions of other calls are normal. Press the volume button There was no lagging situation. If there is a pause when the volume is adjusted, it is basically a problem with the big audio chip. According to the working principle of the hands-free speaker, the hands-free speaker is connected to the power amplifier chip by the tail plug connector. First, measure the 31-pin, 32-pin, 33-pin, and 34-pin diodes of the tail plug connector J1817 and the hands-free speaker. Value to determine whether the line between the tail plug connector and the small audio chip is normal. The J1817 measuring foot is shown in the figure. Then, when measuring the diode value of the I2C2 bus to the ground, it is found that the AP_TO_SPKAMP_I2S2_MCLK data line of the E7 pin has an infinite value to the ground. The position of the E7 foot is shown in the figure. Check the picture and find that there is a resistor R0311 connected between the E7 heel and the CPU. The principle of the R0311 circuit diagram is shown in the figure. The physical location of R0311 is shown in the figure. The diode values ​​of the two ends of the resistance R0311 to the ground are infinite, which is obviously a disconnection between the CPU or the CPU virtual welding problem.
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Measure the 31-pin, 32-pin, 33-pin, and 34-pin of the tail plug connector to the ground diode value is normal. The next step is to check the working conditions of the audio amplifier and whether the I2C1 and I2S2 buses of the communication lines between the audio amplifier and the CPU and the main audio chip are normal. The specific pins are shown in the figure. 
This fault has been repaired several times, but there is a problem with the I2S2 bus from the CPU to the audio amplifier. Generally, this kind of failure needs to be redone for CPU repair. Check the schematic diagram again before preparing to disassemble the CPU. I found that the I2S2 bus also leads to the large audio chip, and the AP_TO_SPKAMP_I2S2_MCLK signal is not connected to the large audio chip. The large audio chip uses the AP_TO_CODEC_I2S0_MCLK signal, and a resistor R0301 is also passed through (see figure) ). The physical location of R301 is shown in the figure.
Directly fly the wire from the position of R0301 near the CPU to the end of the RO311 resistor near the CPU, and borrow the AP_TO_CODEC_I2SO_MCLK signal of the main audio, as shown in the figure. Install the audio amplifier and turn on the system to test the bell. Playing songs, watching movies, and making phone calls are all normal.