PG and FG two pulse signal by digital servo system and to count clock pulses and compared with a reference signal to detect rotation error data and the error data through D / a converter is the DC voltage, and control the spindle motor operation error signal voltage superimposed, from IC20012 pin output to the spindle drive the 12 foot of the integrated circuit IC2071. The driving circuit is controlled according to the variation of the DC voltage of the error, and the output voltage of 9.3V, and 25 respectively from IC20711, and 26 respectively. When the need to stop, the IC200134 pin output 4.9V voltage to the IC207115 pin, the control of the spindle motor to stop.

From the above analysis, we should focus on the detection of IC207112 pin control voltage. In the laser search process, the measurement of 12 pin voltage is 2.5V, normal. Note that the foot before the voltage is normal, should focus on checking the driver circuit and the spindle motor. Measurement of IC207119, 20, 21 foot 12V voltage and 13 pin 5V power supply voltage are normal. As the IC20711, 25, 26 pin voltage is only 2.1V (normal 9.3V) and its 12 foot input control voltage normal, so the fault in the driver IC block and its peripheral components or spindle motor. Detection of the external components of the Holzer components, motor and IC2071 are normal, it is suspected that IC2071 damage. Replacing IC2071 (AN8482SB) after the test machine, troubleshooting.