Printronix L5535, Maintenance Manual

Page: 185 / 358

Drum Motor Control Circuit
II–185
Drum Motor Control Circuit
The drum motor drives the photoreceptor drum. Since the drum is central to
the printing cycle, stable rotation is required of the motor. A rotary encoder is
positioned on the rotating axis of this motor.
A crystal oscillator and frequency divider generate standard pulses that are
equivalent to a motor rotation of 1406.25 RPM. A phase-locked loop (PLL)
circuit compares the motor encoder output pulses with the standard pulses
from the frequency divider. The resulting error voltage changes the motor
drive voltage in such a way that the error voltage is minimized, which causes
the drum motor pulses to occur at the same rate as the standard pulses.
DRMP: Positive side of drum motor drive power supply
DRMN: Negative side of drum motor drive power supply
DME: Drum motor encoder output signal
DMON1: Drum motor drive signal
DMARM0: Alarm signal to indicate rotation abnormality of
drum motor
Drum Motor
Drum Motor Encoder (40 Pulses)
DRMP DRMN DME
Drum Motor Control Circuit
Driver
Circuit
Control Output
(0 to +8v)
(Lock Center
= +4V)
Frequency
Detector
Sensor
Interface
Frequency
Dividing
Circuit
Crystal
Oscillator
DMON1 DMARM0
Gate Array
CPU
MC Board
PLL Circuit