Pioneer FX-K99DK WG Service Manual page 26

9.14 STATIONARY REEL BASE DETECTION (Fig. 38)
This mechanism detects the fact that both motors have
stopped, and is used in detecting the end of tape and the
end of ATSC (for taking up tape slack). The circuit consists
of a differential high gain END SENSE AMP and a Schmidt
'circuit block. The END SENSE AMP non-inverted input is
fixed at a reference voltage level inside the IC, while the
inverted input is passed to an external circuit.
During all modes, current is passed through one motor or
the other. And while either motor is operating, the motor
pin voltage is changed in synchronization with the brush/
commutator switching. When the motors are stationary, the
CONTROL UNIT
Ri8
NF
RIO3 CI3 {
"C14 RIT
4—END SIGNAL
"END SIGNAL
REV REEL
MOTOR
9.15 PLAY MODE
During PLAY mode, constant current is supplied to the
motor to generate constant torque in the take-up reel. If
(PA0008) includes a PLAY CURRENT setting block which
sets the reference current during PLAY mode, CURRENT
AMP 21 which compares the motor current with the
reference current, and another amplifier CURRENT AMP
22 used for current amplification purposes.
33
IC3 PA0008
12 END SENSE
Peel Td
voltage remains at a constant level. In other words, the
end of tape condition can be detected by detecting changes
in this motor pin voltage.
The motor voltage is AC amplified by the END SENSE
AMP, and
if the amplified
output is greater
than the
Schmidt circuit
hysteresis width,
the Schmidt
circuit is
activated. A pulse output synchronized with changes in
the motor pin voltage is generated and passed to IC1.
Therefore, the generation of output pulses indicates that
the motor is operating, while the absence of pulses indicates
that the motor is stationary.
2 SD ¢ eS
PLAY ENO
IC1 PD4022B
FWD REEL
MOTOR
MOTOR OVER SPEED DETECTOR block and. if-it ex-..
a tr