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CIRCUIT DESCRIPTION
VREF Buffer
IC2: CXA1332M
works using the voltage which
is the
half of VCC (1/2 VCC) applied to pin (17): VCTO as a
reference. That
is, the 1/2 VCC
is used
as the signal
ground.
In this unit, since all the power
supply
works
with a
single power, the above 1/2 VCC (VCTO) is buffered by
the voltage
follower
op-amp
IC3 so as to supply
the
power to each block.
Pin
(1) output supplies 1/2 VCC to the following:
CD-CH isolated amp
AUX isolated amp
Analog switch buffer amp
Tone amp
Pin
(2) output supplies 1/2 VCC to the following:
Pre-amp
Power amp input buffer
AC GND of power amp negative feedback
Main in isolated amp
Manual RST (Reset) Circuit
When
the voltage at pin (7) is inverted to high, IC12 is
initialized if pin (28) is at high level.
When
the voltage at pin (7) is inverted to low, IC12
stops its function, and interrupts each power circuit and
this causes shock noise.
Therefore,
Audio
Mute
is activated
by the
collector
output of Q51, while 1C12 pin (7) is controlled with a
slight delay determined
by the time constant
of R189
and C129.
The Voltage charged in C128 is applied to 1C12 pin (28)
via D28 and R188, but the reverse current is inhibited by
D28
even
when
the collector of 051
goes low (Q51
turns OFF), while since discharging is done with a gentle
time constant
consisting
of R187
and C128, the high
level is kept for a while.
BU 5V
1¢12(7)
1cl2
sw
asi
COLLECTOR
aso
BASE
— 250
1e@=
COLLECTOR
1c 12 @8)
MUTE
KRC-851D
1c 2 (7) veto
c3
TO
+8(7.5V)
RST( RESET)
SIGNAL
FOR
CO-OH.
AND
AUDIO
MUTE.
028
TCl2
PIN(23)
MUTE
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