Spacing Drive Circuit - OKIDATA Pacemark 3410 Service Manual

Page: 19
Service Guide PM3410
Chapter 2 Principles of Operation

2.1.06 Spacing Drive Circuit

After receiving a spacing command from the MPU (Q3), the Interface/Motor Control LSI (Q5) outputs the
SPFWD signal to run the DC motor in the forward direction, or the SPRVS signal to run the DC motor in
the reverse direction. This is a fixed pulsewidth signal.
To control the motor speed, Q5 varies the pulse duty cycle according to feedback received from the space
motor. As the space motor rotates, the SPSP Board (inside the motor housing) generates feedback pulse
signals SPfA and SPfB. Q5 detects the edge pulses from these signals and divides the frequency to
output the IPT signal for use in printhead dot timing.
The space motor interlock switch (located at the left side of the shield plate) disables the space motor
drive signals whenever the printer cover is open.
Fuse F1 (3.5 amperes) protects the +38vdc space motor power circuit, should an overdrive condition
exist.
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