Akai AP-206

, ..
through IC1 @, and R3 to IC5 ® as the reset
pulse. The reset pulse of 20 Hz for 33-1/3 rpm or
27 Hz for 45 rpm shaped from the FG signal is
compared with the above-mentioned set pulse
entering IC5 (j), and the output appears at IC5
@.
The output pulse is smoothed by the low-pass
filter, consisting of C9, C10, and R5 through R7,
and enters IC5 CID, then the inverted output is fed
from IC5 CD. The output of IC5 CD fed through
RS and SW903 to IC1 @, in the D.D circuit as the
reference voltage. In short, when the Quartz Lock
Switch SW903 is off, the reference voltage is made
of the +B voltage, while when it is on, the pulse
made of the FG signal is compared with the pulse
generated by the crystal oscillator to produce the
reference voltage. The succeeding operation is
similar to the one when the Quartz Lock Switch is
off.
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3. STROBE LIGHT CIRCUIT
(Refer to the PLL Circuit schematic diagram of the
AP-306/C.)
The 4.4236S MHz signal generated by the crystal
oscillator is delivered through TP-1 to IC2 @. The
Flip-Flop in IC2 halves the oscillation frequency to
2.211S4 MHz. The halved signal is fed from IC2 CD,
to IC3 @. IC3 counts the frequency down to 1/27
for 33-1/3 rpm or 1/20 for 45 rpm.
The count-down signal is fed from IC3 @, to IC4
@.
IC4 further counts the signal down to 160 Hz at IC4
@, 320 Hz at IC4 @ and SOHz at IC4 @ for
33-1/3 rpm or to 216 Hz, 432 Hz and lOS Hz for
45 rpm, respectively. These output signals are input
to the NOR circuit of IC6 Cl ~5). The NOR circuit
outputs from IC6 CD, SOHz signal for 33-1/3 rpm or
10S Hz signal for 45 rpm. The signal is fed through
RIO to TR1 to turn on and off, which flashes the
neon lamp NE90l.
Reference: ~ogic Symbols. and Their Truth Table
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