Tandon TM100-1 Operating And Service Manual page 10

TRACK 0 SWITCH
The Track 0 switch is provided to generate a
logic level at the drive interface, indicating the
read/write head is positioned at the outermost
track.
INDEX SEN SO R
An index sensor is provided to generate
electrical pulses at the drive interface
coincident with sensing Index/Sector holes on
the diskette.
ACTIVITY INDICATOR
An activity indicator, located on the front panel,
is automatically illuminated when the drive is
selected.
1.4 FUNCTIONAL DESCRIPTION
The drives are fully self-contained, and require
no operator intervention during normal
operation. Each drive consists of electronics to
generate and interpret control signals, a head
positioning system, a read/write system, and a
spindle drive system.
When the front latch is opened, access is
provided for insertion of a diskette. The diskette
is held in place by plastic guide rails. Its location
is ensured when the diskette is inserted until a
back stop is encountered.
Closing the front latch activates the cone
clamping mechanism, resulting in accurate
centering and clamping of the diskette. The
drive hub is held at a constant speed of 300 RPM
by a servo-controlled D. C. motor. The heads
remain in contact with the recording media
until the front latch is opened.
The heads are positioned over the desired track
by means of a four-phase stepper motor/band
assembly and its associated electronics. This
positioner uses a one-step rotation to cause a one
track linear movement.
Data recovery electronics include a low-level
read amplifier, differentiator, zero crossover
detector, and digitizing circuits. No data
decoding capabilities are provided.
The drive has the following sensors:
1 . A Track 0 switch detects when the
head/carriage assembly is positioned at
Track 0 .
2 . An index/sensor is positioned to generate
a digital signal when an index/sensor
hole on the diskette is detected.
3 . A write protect switch disables the write
electronics when a write protect tab is
applied to the diskette.
1.5 PHYSICAL DESCRIPTION
A representative drive is shown in Figure 1 -1 .
The drive can be mounted in a vertical or
horizontal plane. However, the logic circuit
board must be on the uppermost side when the
drive is mounted horizontally.
The spindle is belt driven by a D. C. motor with
an integral tachometer. The servo control
circuit and tachometer control the speed of the
spindle.
The read/write head assembly is positioned by a
split band positioner mounted to a stepper
motor. The read/write head(s) is a glass-bonded,
ferrite/ceramic structure with a life expectancy
of 20,000 operating hours.
The electronic components of the drive are
mounted on two printed circuit boards. The logic
circuit board is mounted above the chassis. The
spindle motor control circuit board is mounted
at the rear of the chassis. Power and interface
signals are routed through connectors plugged
directly into the logic circuit board.
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