Teac C-1 Service Manual page 41

TAPE TRANSPORT SECTION
route (2). The head solenoid operates when Q531 is turned
on. The brake solenoid operates when Q532 is turned on.
When current flows in the solenoid, the potential at point
(A) falls to about +24V.
When Q523 is turned on, the current in the route (3),
which charges C522 and turns on Q524, is interrupted.
Thus, the charge in C522 is discharged via route (4). After
C522 has discharged, Q524 turns off and then Q525 and
Q534 also turn off.
When Q534 turns off, the high voltage supply to solenoids
in the route (5) stops, and the solenoids are maintained at a
low voltage by route (6) (about +10V).
Solenoids are supplied +24V for about 200 milliseconds.
When Q522 is off in the STOP mode, C521 is charged via
route (7) and Q526 is turned on by the current in route
(8). When Q522 turns on, current in routes (7) and (8) is
interrupted and the charge in C521 is dischraged through
route (9).
After C521 has discharged, Q526 turns off and then Q527
turns on and then Q533 turns on, and the pinch solenoid
operates.
Owing to the discharge of C521, the pinch solenoid is actu-
HIGH
Pin #17 of usor
Low
HIGH
Pin #18 of U5OI
Low
OFF
Q522,053!
ON
OFF
0523 ,0532
ON
©
OFF
0524,0525,0534
ON
33V
® 24v
lov
HEAD SOLENOID ) 2év
BRAKE SOLENOID/ [Ov
ov
®
OFF
0526
ON
OFF
0527 ,Q533
ON
©
Q529, Q530,Q535
©
PINCH SOLENOID
33V
zav
jOV
24Vv
tov
ov
fe | LARGE
current
SMALL
°
STOP
Ce | oevar
PLAY
Approx.
200m Sec
Approx: Approx.
1SOmSec 200mSec
ated about 150 milliseconds after the head and brake
solenoids. This time delay is to take in the slack in the tape
to stabilize the tape transport.
(The status during the 150 milliseconds from actuation of
the brake and head solenoids to that of the pinch solenoid
is the same as in the PAUSE mode. In the PAUSE mode,
weak current flows in both the right and left reel motors to
pull in the slack in the tape. Details are given in the Section
4. (3). )
If the PAUSE button is depressed during the PLAY mode,
the pin 17 of U501 goes low while pin 18 goes high.
Head and brake solenoids are kept in the operation status
by current in route (10) and (11) respectively.
The pinch solenoid is turned off because Q526 is turned on
by the current in route (12) and then Q527 and Q533 are
turned off. As a result, the tape is not driven any more
and stops running. When such a condition occurs, weak
current flows in the right and left reel motors to tighten
the tape as previously described.
The above operations are shown in the timing chart Fig. 10.
PAUSE PLAY
Approx.
200mSec
T-1295
Fig. 10 Timing Chart of Solenoid Operation