discharge. Another special feature of the on-off cir-
cuit is the instantaneous return to a 2 second delay,
even if the AC pushbutton is pushed off and back on
very quickly. On and off switching transients are
never heard from the C 30.
AUTO TURN ON:
A turntable plugged into the green outlet at the
rear of the C 30 can control the on-off operation of
the C 30. Current flow to the turntable is sensed and
controls a silicon control rectifier (SCR). When the
SCR conducts a relay closes. This relay turns on
power to the C 30 and to the black AC power outlets.
A current sensing sensitivity control allows calibra-
tion of the Auto Turn-On circuit to the turntable.
Power is also controlled by the C 30 Power On
pushbutton. The Auto Turn-On circuit may be
switched off for manual power control.
POWER SUPPLY:
To eliminate possibility of hum radiation, the
power transformer is double shielded with a copper
strap and steel end housings. The transformer main
output voltage is fed to a full wave bridge rectifier.
Filtering is done with two 3300 microfarad filter
capacitors to provide the +30 volts and -30 volts
DC. The plus and minus 18 volts needed for low level
and operational stages is stabilized by integrated
circuit voltage regulators.
20
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