AMT Datasouth Accel-7350 Service Manual page 84

Drive method
Data control signals from gate array consist of speed control and phase signals. The speed
control signal is set at a certain voltage level by transistors QA10, QA11 and resistor R167,
R172 and R179, and is supplied to U22. This voltage level determines how U22 controls the
current, which flows to the motor.
LF motor (rear) drive circuit (LFB)
LF motor uses a 4-phase stepping motor, and it is set in single-phase excitation by
MB90705H at standby and double phase excitation at rotation of the motor.
Current value, which flows to the motor, is decided by turning on LFBDR0-LFBDR2.
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