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TC-766-2
7.
Tape Tension Set-up and Circuit Operation
(Refer to Figs. 6, 7)
In order to make tape tension constant, torque
at the start of tape winding (slow revolution) must be
increased
and
torque near the end of tape winding
(fast revolution) must be decreased.
1.
Ata slow revolution speed, the pulse interval is
long so that the dc voltage output @ becomes
high; hence supply reel motor torque becomes
large.
At a fast revolution speed, the pulse interval is
short
so that the DC voltage output becomes
low making the supply reel motor torque small.
Even if the tape speed is varied, if the radius of
the remaining tape is the same, the back tension
has to be the same.
Therefore, when changing
from 19cm/s (7% ips) to 38 cm/s (15 ips) with
switch (S602-1), Q730 is turned ON
and half
cycle of the input signal to switching transistor
(Q731) is turned OFF to produce the specified
- torque.
Q730
Be
$6Q2-
|
TAPE SPEED
19cm —= 38cm
flip-flop
schmitt circuit
differential amp
19cm
38cm
o
AVAvaws
STATA
(Output from FG — differential amplifier)
en
TUL
(3) ss ae pees
1 nm n
On : } (Make a square wave by means of the Schmitt. circuit)
@ _K.
4
ph po
;
(Constant pulse width attained by flip-flop circuit)
6
FLT
TULLE LL
No output with Q730 ON
'6
If reel radius is the same, T79=73g
7)
I a
|
{Pulse for switching Q731)
rs)
is ' le
[vis
4 i id is v8
If reel radius is the same, V1.9
= V3g
(Q731 charges at B+ and discharges during switching)
(9)
Sa
ee
eI
~~
r
(DC voltage for motor drive)
Fig. 7
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