Standard top loading cartridges are fitted
with
an
armature plate having one notch which is
the
Index notch. Some specially modified
top
loading cartridges
will
have. in addition
to
the index notch, notches used for purposes
of
mechanical sectoring.
Standard front loading cartridges have
slots
for the purpose
of
mechanical sectoring. and
a single index slot. The sector
slots
and the index
slot
are located
in
the sector ring. Some
specially deSigned front-load cartridges have
only
an
index
slot
in the sector ring.
Front loading models
of
the 03000 employ a photoelectric type
of
sensor
for
the upper
sensor. Top loading models use a magnetic transducer
for
the upper sensor.
On
all
models, the lower sensor is a magnetic type transducer. The upper sensor
for
front loading
models connects to J112. pin 9 (zone
H20). For top loading models, the upper sensor is
connected to J112, pin 6 (zone
G20).
U425
(zone G20) serves as a fixed voltage gain
amplifier
when the magnetic sensor is
connected and functions as a current-to-voltage converter when the photoelectric sensor
is connected. Gain
for
the circuit is established by
R28, R29,
and
R30
(or W19)
for
the
magnetic sensor connection and by
R27,
R29, and
R30
(or W19), for the photoelectric
sensor.
C5
determines the band
width.
C6
and
C7
decouple power supply voltages
for
U425. The signal from
U425
is coupled
to
a voltage
follower
U387 by
an
R-C network,
Ca
and
R31.
The
output
of
the voltage follower, U387, is fed directly to a
Schmitt
trigger comprised
of
one section
of
U409
(zone G18). The
Schmitt
trigger threshold is determined by
R35,
R33,
R32,
and the + 5.0v power supply voltage. The
output
of
the
Schmitt
trigger is buffered by
U408-8 and fed
to
the Upper Time-Demultiplexer. The signal at
this
point
will
be a
pulse-train
with
one pulse per slot,
or
notch detected by the sensor. The purpose
of
the
Schmitt
trigger then is
to
convert the analog signal from the
amplifier
circuits
into
a
digital
signal suitable for use
in
the Upper Time-Demultiplexer and the remainder
of
the logic.
Referring
to
J112 (zone 018) it can be seen that power
for
operating the photoelectric
sensor for front load machines is
supplied via
this
connector.
The lower-sensor detector
functions
in
a manner
similar
to
the upper sensor detector. The
lower magnetic sensor connects
to
J112, pin 4 (zone F20). The
output
of
this
sensor is
filtered by
R36
and C12; then fed directly to a
Schmitt
trigger
consisting
of
the other half
of
U409 (zone F19). The threshold
for
the high threshold mode is determined by
R43,
R42,
R39.
R37,
and
R38.
For the high threshold mode the
output
transistor
of
U444-4 (zone
E19)
will not be conducting; therefore
R40
will
be essentially open circuited. In the low
threshold mode, which
will
be the case whenever Drive Motor Enable (LDMEG) is low, the
end
of
R40
which is connected
to
U444-4 will
be
essentially connected
to
ground.
Therefore, the threshold
for
the low-threshold mode
will
be
determined by
R43,
R42,
R40,
R39,
R37,
and
R38.
The output
of
the
Schmitt
trigger is buffered by U408-4 and U408-2 and
fed
to
the Lower Time-Demultiplexer.
In
addition, U408-4 also feeds the Lower Detector
Pulse (LLDPG)
to
the Disk Rotation Detector Counter (sheet one
of
the schematic) for
detecting disk rotation.
The pulse trains obtained from the Sensor Detectors
will
have
an
index pulse intermixed
with
the other pulses
if
the sensor is detecting
multiple
notches. This,
of
course,
will
be
the case at
all
times
for the Lower Magnetic Sensor which senses the Phase Lock Ring.
However, the pulse obtained from the index notch from the
Upper Sensor
will
be
inter-spersed with the pulses obtained from the sector notch
only
if
it is a
multi-notch
5-37
6300
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