ELECTRONICS
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THEORY OF OPERATION
POWER-UP SEQUENCE
By observing the power-up sequence of the
TC 4100, one can usually determine if any
problems exist with the motors or sensors.
The following sequence should occur after
first turning on the main power switch on the
front panel:
Power-up Check
1) The cleaner lift if up, will drop to its
"down" position.
2) Threading arms, if out, will move to their
"in" home position.
3) Carrier lift, if down, will now cycle to its
"up" position and stop.
4) Cassette loading rollers will turn (trying to
un-load a cassette) for approx. 4 seconds.
5) The spindle slides will now cycle to the
"large" position and back to the "small"
position.
6) The cleaner lift will return the cleaner
module to its "up" position. The cleaner stays
up, to facilitate the changing of the cleaning
tissues, unless the machine is threading a tape.
TAPE LOADING SEQUENCE
The insertion of a cassette in the loading slot
should cause the following sequence of events:
1) As the tape is loaded an infra-red sensor in
the carrier is blocked, signaling the presence
of a cassette.
2) At the back end of the carrier are two
sensors that dertermine whether the cassette is
loaded partially(one photocell blocked) or all
the way(2 blocked).
3) Once the loading rollers have shut off, the
cassette size is determined by two photocells
that look for the presence of a large cassette.
If the spindles are not at the correct position
for the cassette, the spindle-mover motor
slides them to the proper position. The reel
spindle position is sensed by two
microswitches in the spindle-mover cam
notches.
4) The cleaner lift motor now drops the
moveable cleaner to its "down" position. Two
microswitches sense the lift motor cam
position.
5) The carrier lift is now turned on to lower
the cassette carrier to its"down" position. If
the "carrier-down" optical interrupter sensor
does not become blocked, the carrier continues
to cycle until it gets this signal. If this
happens, something is preventing the carrier
from going down fully.
6) When the carrier is down, the cassette is
now sitting on the locating pins(hex posts.)
Microswitches, actuated by plungers through
the panel, now read the reel hub size, metal/
oxide tabs and the erase protection tabs on
small and large cassettes.
7) The threading arm motors (Bi-directional)
now move the threading arms, and tape, to
their "out" position. The motors continue to
be powered in the outward direction, forcing
the arms against the outer limit stops ( with the
help of slipping clutches) until both arm-out
microswitches are tripped.
8) The final step is for the cleaner to lift to its
"up" running position.
The machine is now loaded and ready to run
the tape. It will wait for a transport key
command by the operator to run FWD, etc. .
Due to the smart electronics, however, the
machine will accept a transport command
during the loading process. Normally the
operator presses AUTO which will cause the
tape to run forward and rewind back to the
beginning.
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