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ELITE SERIES USER MANUAL THEORY OF OPERATION
7.1.4. Head Positioning Mechanisms
An electrical stepping motor and an advanced
head positioning mechanism position the read/-
write head. Clockwise and counter-clockwise
rotations of the stepper motor are translated
into linear head movement via one off two mecha-
nisms discussed below. The Apple system software
increments the stepper motor to the desired
track by directly signalling the drive electron-
ics which stepper motor phases to power on and
off.
The stepper motor stator coils are organized in
four phases: A, B, C, and D. As each phase is
activated in turn, the motor rotates to align
with that coil, forcing the carriage to move one
“halftrack” (full track for Elite Three) posi-
tion. It the phases are activated in the order
A, B, C, D, A ... the head will step in. The
order D, C, B, A, D ... will cause the head to
step out.
Band Pulley Positioning
In- the Elite Two, Three, and some Elite Ones,
the stepper motor acts on a pulley to which is
attached a flexible, ultra thin band. One half
of this band has a slot through which the other
half passes after looping around the pulley.
The two band ends are secured to the main head
carriage at the inner and outer edges. Slack-
ness in the band or the motion of the mechanism
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