AN7108 Walkmanship ----- AN7108 WALKMAN

I. Introduction to the principle of circuit Single chip three-dimensional playback circuit AN7108 contains dual front amplifiers, dual power amplifiers, volume controllers, filters and reference voltage sources (5, (16) feet), and the like. The left and right channel audio signals picked up by the magnetic head are fed from 3, 6 feet. After the pre-placing, the volume control and power amplification, by the (14), (11) foot output, driving through coupling capacitors C11, C12, and socket CK Stereo headphone sounds. R1, R3, R5, C3, C5 and R2, R4, R6, C4, and C6 formulate a prodeent negative feedback network, and RP1 is the volume potentiometer, C1, C2, C13, C14 are input and output stage high frequency denoising capacitance. The AN6650 is a steady speed control circuit of DC motor, its operating voltage ranges from 1.8-7.0V, and the limit power consumption is 750MW. RP2 is a motor M rotational speed adjustment potentiometer. C17, C18 is a high frequency noise reduction capacitor. Second, common troubleshooting 1. Motor does not rotate Usually the battery GB capacity, the SW contact is poor contact, the motor M is damaged, the bearing deficiency and the rotor are caught by foreign bodies, etc.), the adjustment potentiometer: RP2 is poor, AN6650 pin is welded or printed Copper foil fracture and the AN6650 damage. 2. The motor turns normal. But the play is silent First check if the headphone cable is coming, the headphone socket CK and the head are good. Then the AN71085, (16) the reference reference voltage (normal value of 1.4V and 2.4V), if low, may be the filter capacitor C8, C15 leakage. Then, the foot voltage is then measured, and the range of variations at the end of the volume potentiometer RP1 should be 0 to 1.4V. Otherwise there is a problem with RP1 or C16. If the above examination is normal, the pliers can be touched with the AN71083, 6 feet, such as the big interference sound in the earphones, indicating that the power discharge circuit is good, may be the magnetic head and lead opening and C1, C2 breakdown. If there is no sound in the headphones, the measured power amplifier output foot (11), the (14) foot voltage is close to 1 / 2Vcc, if 0V or VCC. Explain that the power amplifier is bad. 3. Small play sound Tune the volume potentiometer. If the volume is changed, it is small, and the RP contact is poor. If the RP1 does not work, you should check the power supply voltage and coupling capacitance C11, C12 filter capacitor C16, and the like. 4. Loud voice If there is only noise when using an external power supply, you should check whether the filter capacitor C8, C15 is open, the failure or capacity is small. If there is also noise using the battery, you should check that the magnetic head ground wire and the movement of the movement are not broken. In addition, when the motor is poor (such as brush contact with poor fire, the bearing is deficiencies, and the lags are delayed) can also cause large noise.