Broadcast Electronics 3000 Series - Optional Q-Trip Sensors; Stop;Start Logic; Power Supply Board; Configuration

Following Q7 the audio signal is fed to LC filter L1, C41, and
to IC-48 for amplification. The output is rectified, filtered, and fed to
comparator IC-68.
With 3 kHz tone present at the filter, the output of
IC-68 goes high to deliver a positive pulse through CR13 and C39 to the
stop
control.
4-6. OPTIONAL Q-TRIP SENSORS
When equipped with the optional QI 150Hz and QII 8kHz auxiliary
cue tones, separate sensors are installed. These are similar in operation
to the 1
kHz sensor. Signal is taken from the output of the cue track
booster
amplifier (IC-28) through separate level controls to a fixed tuned
active filter. The signal is then rectified and fed to a comparator which
delivers a +VDC output during tone presence to drive relays located on the
power supply. To prevent chatter by these relays when the ac power is turned
on,
C36 keeps the reference voltage higher than normal until the circuit
stabilizes. At turn-off, C61 and CR24 hold the reference voltage as the
power supply shuts down. Muting is accomplished by grounding the input to
the comparator
by the fast forward cue shift/mute bus. The 150 Hz (01) tone
is sensed by IC-58, IC-6A while the 8kHz (011) tone is sensed by IC-5A and
IC-6C.
4-7. STOP/START LOGIC
Stopping and starting are controlled by the flip-flop composed of
Q8 and Q9. The circuit is a bistable multi-vibrator in which Q9 is con-
ducting
and Q8 is off, or Q8 is conducting and Q9 is off. When Q8 is off
the collector is not drawing current and is at a 18 VDC level. This voltage
is carried through R52 to the base of Q9 to hold Q9 in full conduction.
Likewise,
when Q9 is off, the voltage from its collector goes to the base of
Q8 through R53 to hold Q8 in full conduction. The flip-flop will change
state when a positive voltage is applied to the base of the non-conducting
transistor. This is accomplished through coupling resistors R61 and R61.
To prevent false triggering, capacitors C60 and C33 shunt short duration
transient pulses to ground. When power is first applied, R54 ensures that
the flip-flop will set to stop with Q9 conducting. The output voltages from
Q8 and Q9 are available on the board pins M and 9 for use in the logic on
the power supply and record boards.
4-8.
POWER SUPPLY BOARD
4-9. CONFIGURATION
The Power Supply board contains the +24 VDC supply for the elec-
tronics, the +30 VDC supply and controlling circuitry for the solenoid, and
the logic driver circuits. In units equipped with the optional Q-Trips,
the
QI 150 Hz and QII 8 kHz relays are mounted here. In units equipped with
the optional
fast forward provision, the motor control circuitry is incor-
porated
on the Power Supply. The Power Supply is manufactured in four
versions.
The schematic diagram included shows the most complex configur-
ation in which the Q-Trip and fast forward options are both included. The
assembly diagram with parts lists is also included.
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