Tapeend Ditection Circuit - Teac C-1 Service Manual

TAPE TRANSPORT SECTION
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Fig. 14 Recording and Record Muting Circuit
2-7 TAPE END DETECTION CIRCUIT
The ring magnet shown in Fig. 16 is mounted on the shaft
of the relay pulley transmitting the right reel table rotation
to the index counter, and rotates as long as the tape is run-
ning. The hall effect element converts the change in mag-
netic field due to the ring magnet rotation into an electric
signal. The output signal of the hall effect element is
amplified by the differential amplifier comprising Q622 and
Q623, and turns on and off Q621. (D621 is used to dis-
charge C621.)
C515 is discharged faster by route (2) compared with route
(1). Thus, while Q621 turns on and off repetedly, the
potential at the point (D) does not rise and Q510 and Q509
are held off. When the tape stops running at the end, the
ring magnet also stops rotation and the hall effect element
outputs no signal. Thus, Q621 is held off and C515 is
discharged in the route (1). When the potential at the point
(D) reaches about +7V, Q510 turns on and then Q509
turns on and supplies a high level signal to the subsequent
stage, About one (1) second delay time elapses after the
tape stops until the detection signal is sent.
When the deck stops operation and the brake solenoid
turns off or in the PAUSE mode or during the tape loading,
a high level signal is applied to the base of Q511 to turn it
on. While Q511 is on, the operation of the tape end detec-
tion circuit is inhibited.
HALL EFFEC
ELEMENT
D62i R625
PAUSE
LOADING
INHIBIT SIGNAL
{HIGH LEVEL)
B
RAKE SOLOoD!
Fig. 16 Tape End Detecting Circuit
©
©
BRAKE SOL.
T-1300
TAPE END
i
PLAY DELAY sToP
4
Approx. 14SEC
HIGH
LOW
:
I3V |
i
T-1302
Fig. 15 Waveforms of Each Part of Tape End
Detection Circuit (numeric value omitted)
TO END STOP CIRCUIT
(Q520 , Q521)
TO AUTO REWIND
CIRCUIT{S704)
T-1301
13