Kenwood PR-657, Instruction Manual

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Main Power Source
The input AC voltage is fullwave-rectified by D1 (KBPC-
2502 bridge), is smoothed by C1 (15,000
M
F ) , and is fed
to the Current Amplifier.
Auxiliary Power Source
This power source feeds ±15V regulated voltages to the
voltage control circuit and protective circuit. The input
voltage is full-wave rectified by D101 through D104 and
is regulated to ±15 V by O t 0 1 , D105, Q102and D106.
The +15 V voltage also is used to create a highly-stable,
accurate 6.2 V reference voltage through D107 a high-
temperature compensation zener diode D108. The vol-
tage obtained at D107 is used as the reference voltage for
the overcurrent protective circuit.
Differential Amplifier
This amplifier controls the output voltage, being com-
prised of IC101, Q103, Q104 and Q105. The output
voltage can be varied with V R 1 . The adjusted voltage is
amplified by IC101, is passed through Q103, and is
voltage and current-magnified by Darlington amplifier of
Q104 and Q105. The magnified voltage is fed through
the emitter follower to the succeeding Current Amplifier
stage. The Differential Amplifier is stable and quick in
responding to a load change and the like so that IC101
is of open loop amplifier.
Overcurrent Detector
This detector is a protective circuit that prevents an
overcurrent, being comprised of Q106, IC102 and Q107.
The voltage induced across the output current detecting
resistor R12 is compared with the reference voltage
given at D107 in the comparator circuit IC102. If the
output current reaches its overcurrent limit, IC102
operates, the output of which prompts Q106 to turn on
to suppress the base potential of Q104. This prevents
the output current from increasing more than limited.
The Overcurrent Detector I has a drooping constant-
current characteristic. When the protective circuit is in
action, Q107 turns on the light-emitting diode D3,
which indicates such an action.
Current Amplifier
This current amplifier consists of Q1 through Q7, 0 1
being an emitter follower. The remaining Q2 through
Q7 are connected in parallel.
Light
This light is an overcurrent indicator light-emitting diode
(LED).
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