c. A slight delay in time is allowed for the
supply
reel,
which
has
appreciable inertia, to start turning at operating speed.
d. The tension idler ((m), fig 1-9b) and back-torque work together to smooth
out irregularities caused by the rubbing of the tape against the supply reel ((p),
fig 1-9a) sides, sticking together of tape layers, or other causes.
3.
Again looking at Figure 1-9a, note that the tape is drawn from the tension
idler, across the rolling tape guide, erase head, tape guide, record head, tape
guide, and reproduce head. The force, which draws the tape across the heads at a
constant speed, is provided by the capstan and the capstan pressure roller.
a. The combination of the capstan, the tension idler, and the reverse torque
of the supply reel keeps the tape under constant tension.
There is friction
between the tape and the stationary heads. This friction is a source of vibration.
Attempts to eliminate this vibration are included in the design of the transport
mechanism by using a rigid base on which to mount the transport components.
b. Other causes of vibration are the amount of wrap around the head,
smoothness of head faces, tape tension, tape condition, tape composition,
temperature and humidity.
c. The capstan may be either the shaft of the drive motor or a shaft driven
through a speed-reducing mechanism. The capstan and any associated mechanism must
be made with precision or it will cause problems during both record and playback.
d. This requirement for precision components includes the drive motor, as it
must drive the capstan mechanism at a constant speed.
4.
Immediately following the capstan and the capstan pressure roller is another
tape guide. Each tape guide serves to keep the tape in alignment with the heads at
all times.
a. If the tape guides permit any vertical variation of the tape,
a
possibility exists of attenuation of the recorded signal during reproduction.
b. In extreme cases the signal could be lost entirely, or the erase head
would either fail to erase or improperly erase when a recording is made.
c. The tension idler near the takeup reel serves the same purpose as the
other tension idler. The torque on the takeup reel changes according to the amount
of tape on the reel.
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