Pioneer A-7 Instrukcja serwisowa - Strona 27
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Drukuj stronę11. ADJUSTMENTS
@
Idle Current Adjustment
1.
Depress the speaker A switch to the ON posi-
tion and connect an 8 ohm load to the speaker
A terminals.
Turn
the volume
all the way down, turn the
power ON and let stand for 10 minutes.
Connect a DC voltmeter to emitters Q1 and Q2
and adjust VR1
so the voltage difference be-
tween the emitters is 44mV.
Bottom (capacitor assembly GWR-131)
4,
A-7
In the same manner, connect a DC voltmeter to
emitters
Q3 and @4 and adjust VR2
so the
voltage
difference
between
the
emitters
is
44mV.
NOTE:
When
connecting
a voltage
meter
to the transistor emit-
ters, refer to diagram 11.1 to make sure no misconnections
have
been
made.
All connections
are performed
on
the
bottom plate of the amplifier.
VR
Lch
2/Rch
VAI
Fig.11.1
The idle current adjustment
Adjustment of power indicator
Connect
the
frequency
oscillator
to
AUX
terminal and send a signal of 1 kHz, 150 mV.
Connect
the
AC
voltmeter
to the
speaker
terminal and adjust the volume so as to allow
the output to be 20 V.
Under
this
condition,
adjust
with
VR101
(Lech) so as to allow red light emitting
diode
(LED)
of power
indicator
to start lighting.
In the same manner, adjust with VR102 (Rch).
Fig.
11-2 The adjustment of power indicator