Teac C-1 Service Manual page 37

TAPE TRANSPORT SECTION
Pin 11,13:
These input terminals are grounded to hold them low,
because the REW function is not provided in the C-1.
Pin 12, 14:
These pins are grounded and therefore at low level.
If the PAUSE button or the PLAY button is depressed
in the F. FWD mode or the REW mode in this condition,
FFO or RWO falls to the level while SBO or PYO goes
high.
Pin 15 \ 18, 20 and 21: Output Terminal
All output terminals of the LSI are open drain. Signals
are output at the high level. The output voltage is
Vss -1V when the output current is SmA. The LSI
of C-1 is designed so that all load currents are kept
below 25 mA. Therefore, the output voltage is higher
than +11V.
Pin 19,22:
These two output terminals are unused.
Pin 23: GND terminal
Pin 24: Clock input terminal
A clock signal of 40 to 50 kHz is required to operate the
SYS-CON. If this clock signal is not generated cor-
rectly, all of the C-1 operations are not ensured. Q504
and Q505 comprise the clock oscillator. The oscillation
frquency is about 45 kHz.
1-3 OPERATION
(1) Input priority
The input priority of the signals is predetermined. If two
or more signals are input simultaneously, the output is
determined according to the priority of the input signals.
Input signal priority is as follows (from higher priority to
lower).
(1) RES (RESET) (2) STI (STOP) (3) SBI (PAUSE)
(4) PYI(PLAY) (5) REVERSE (unused in C-1) (6) FFI
(F. FWD), RWI (REW)
For example, if the STOP button and the PLAY button are
depressed at the same time, the SYS-CON outputs the
STOP signal according to the input signal priority, and the
tape deck is set in the STOP mode.
Note that when two buttons are released at the same time,
the operation mode of the button which is released later is
selected. FFI and RWI both have the same priority. When
the F. FWD button and the REW button are depressed at
the same time, both FFO and RWO signals are output.
In this case, the REWIND mode is selected in C-1 by the
reel motor control circuit.
Fig. 6 Clock Signal Oscillator
+13V ( | | ( |
Ov
I6uSEC
23SEC
Fig. 7 Clock Signal Waveform
(2) Record delay operation
When the operation is changed over from REC/PLAY or
REC/PAUSE mode to STOP, F. FWD or REW mode,
SBO or PYO falls to the low level about 45 milliseconds
after RCO (when the clock frequency = 45 kHz), FFOor
RWO rises to the high level after SBO or PYO falls to the
low level. This time delay runs the tape until the recording
bias has stopped after completion of the recording opera-
tion. A click may be recorded if the tape is removed
from the recording head while the recording bias is still
effective. The time delay results from dividing the clock
signal frequency. Therefore, the delay time becomes short-
er if the clock signal frequency is high, and it becomes
longer if the frequency is low.