Realistic STA-21 - Alignment Instructions

4.
ALIGNMENT
INSTRUCTIONS
MAIN
AMPLIFIER
AND
RESET
CIRCUIT
ADJUSTMENT/CHECK
NOTE
o
Maintain line
voltage
at
120 volts.
(UL,
C.S.A.)
(Use
220/240
VAC
For
European
&
Australian Models.)
o
Set SELECTOR
Switch
to AUX.
.
Set
MODE
Switch to STEREO.
o
See
P.C.B.
illustrations for
alignment
points/adjustments.
MAIN
AMPL!FIER
ADJUSTMENT
STEP ADJUSTMENT
EOUIPMENT
CONNECTION AUDIO
FREO.
LEVEL
ADJUSTMENT
1
Check
DC Balance
by
measuring
DC voltage
across
Output
of L and
R
channel.
DC Volt
Meter
See Fig.
1
No signal
DC
voltage
should be
less
than
30 mV.
Select of
8305(L
channel)
R306(R
channel)
2
ldling current
adjustment
DC
Volt
Meter
See Fig,2
No
signal
Adjust
voltage
across
Emitter
resistors
R321
and
R322
to
10
mV.
(8
0
Load)
R329
R330
0-30 mV
Main
Amp
Figure
1
(-30
mV to +30
mV)
Reset
Lamp
8
ohm
load
Speaker
Output
Oscilloscope
(When
protector
circuit is
activated)
E
Oscilloscope
Osc
Hz)
Adjust
Volt
Meter
for
10
mV
Main AmP
Figure
2
RESET
CI
RCU
IT ADJ
USTM ENT
STEP
ADJUSTMENT
EOUIPMENT
CONNECTION
AUDIO
FREO.
SETTING
LEVEL
ADJUSTMENT
1
Turn trimmer resistor
R
332 counterclockwise
(minimum
value).
2
Audio Osc.
V.T.V.M.
Figure
3
1000 Hz
VOLUME:
Max
BASS, TREBLE
& BALANCE:
Center
Adjust
input
to
AUX 1
to
get
output
level
of about
3
Volts
(8
ohm
load)
3
Reset
circuit
adjustment
Audio
Osc.
V.T.V.M.
Figure
4
1000
Hz
Same as
above
Adjust
R
332 so
output drops
to zero
(RESET
comes
"on")
when
output
speaker
terminals
are shorted:
DO
NOT
ADJUST
PAST
THIS
POINT.
R 332
Figure
3
-7
-
AC V.T.V.M.
(3V)
Figure
4