TM 32-5835-001-24 & P
(4) Tape drive system. The purpose of a recorders to make a record on tape
of signal data which may be recovered in its original form at a later date. This is
accomplished by moving a magnetic tape past a record head. The input data signal
changes the magnetic field generated by the head, which in turn changes the mag-
netic flux of the iron oxide particles on the tape in accordance with the applied sig-
nal. Data is then reproduced by moving the magnetized tape past a reproduce head
to induce a voltage in head windings equivalent to changes in flux. Since, in analog
recording the data signal is a function of the time and amplitude of the magnetic field,
it is essential that the tape be moved past the reproduce head at the same rate it was
moved past the record head originally. Therefore, the primary function of the tape
drive system is to move the magnetic tape in a smooth and uniform manner past the
record and reproduce heads to preserve the fidelity of the data signals with regard
to time. This is accomplished by a dual capstan drive system when the unit is oper-
ated in the record or reproduce mode. In the modes F/F (i.e., Fast Forward) and
F/R (i. e., Fast Reverse) the tape is moved by the reel drive system only and speed
is not regulated.
(5) Capstan drive system. Refer to figure 3-2. The recorder uses a dual cap-
stan drive to provide positive control of tape motion. During recording and repro-
ducing, the tape leaves the supply reel (in cassette), is fed over a tape guide be-
tween the input capstan and pinch roller, and past a tape guide to the takeup reel
(in cassette). The stability of the linear speed of the surfaces of the capstans
determines the precision with which the tape is moved in the record and reproduce
modes. For this reason, a capstan motor servo circuit (figure FO-6) is used to
minimize speed than ges of the capstan drive motor due to variations in torque loading
supply voltage. The capstans are belt driven by the servo controlled drive motor
and the pinch rollers clamp the tape to the capstans in the record and reproduce
stans operate at slightly different speeds with the exit capstan rotating slightly
faster than the input capstan. This differential speed produces a controlled tension
in the head area which greatly reduces the possibility of tape-to-head separation
during vibration, shock, or acceleration. The mode selector switch on the front panel
is mechanically attached to the slide plate assembly so that the pinch rollers are en-
gaged and the audio head is in contact with the tape when the record or reproduce
modes are selected. When the mode selector switch is in the F/F mode, F/R mode,
and OFF mode, the pinch rollers and head are retracted and tape movement is con-
trolled by the reel motor drive system.
(6) Reel motor drive system. Figure 3-3 is a functional schematic of the elec-
tromechanical system used to drive the tape reels (within the tape cassette). The
function mode selector 3A4S1 on the front panel is physically connected to a slide plate
on which idler wheels A and B are mounted. By proper positioning of the mode sel-
ector knob, the main slide plate is moved in or out and a cam plate is moved to one
side or the other to engage one or the other of the idler wheels with the reel motor
drive shaft and the rubber-covered reel drive hubs. Idler A is used to drive the
reels in the fast forward and fast reverse modes. When the mode selector knob is in
the F/R position, idler A is moved into contact with the motor drive shaft and one
drive surface of the supply reel hub. The ratio of the diameters is such that the
reels are driven at the selected fast speed (forward or reverse) . When the mode
selector knob is pushed in toward the panel and turned to the REC or REPRO posi-
tion, idler A is moved out of contact with the reel hubs and idler B is moved into con-
tact with the motor drive shaft and the take-up reel hub drive surface. This provides
3-2
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