Fisher CA-224 - Page 7

RECOMMENDED
TEST
EQUIPMENTS
The
following
test
equipments
are
recommended
to
completely
test
and
align
the
Amplifier:
e
Line
Voltage
Isolation
Transformer
e
Low-Distortion
Audio
Sine-Wave
Generator
e
AC
DC
Multimeter
e
Harmonic
Distortion
Analyzer
e
Accurately
Calibrated
AC
Voltmeter
e
Two
(2)
Load
Resistors
8-ohms,
250
Watts
e
Oscilloscope
(Flat
to
100 KHz
Minimum)
(Minimum
Rating)
HARMONIC DISTORTION TEST
CAUTION: Limit the following tests to no more than ten
minutes each. Use 8-ohm resistors, with a minimum
power rating of 250 watts when connecting a load across
the SPEAKERS terminal.
CONTROL
SETTINGS:
ONE
CHANNEL
DRIVEN:
Unplug
the
AC
power
cord
and
set
the
front
panel
1)
Connect
a
low
distortion
audio
generator
io
LEFT
controls
as
follows:
CD
IN
jack.
Set
generator
frequency
to
1
kHz
and
output to minimum.
2 GRAPHIC EQUALIZER to center position.
2) Connect an 8-ohm load resistor between SPEAK-
e
BALANCE
control
to
center
position.
ERS
SYSTEM
LEFT
and
COM
terminals.
Connect
a
Harmonic
Distortion
Analyzer
and
an
AC
VTVM
in
e
POWER
switch
to
OFF
parallel
across
the
8-ohm
load.
»
FUNCTION
switch
to
CD
3)
Connect
the
AC
power
cord.
Turn
VOLUME
control
to
MAX.
e VOLUME control to MINIMUM position
4) Increase generator output for 35 Watts RMS (16.7
e
LEFT
CHANNEL
DRIVEN
volts
across
the
8-ohm
load).
Harmonic
Distortion
Analyzer
should
measure
0.5
%
distortion
orless.
5) Repeat steps 1 through 4 for RIGHT CHANNEL.
BOTH CHANNELS DRIVEN
Connect
8-ohm
load
resistors
across
LEFT
and
RIGHT
SPEAKERS
SYSTEM
terminals.
Adjust
gener
-
ator
output
and
“VOLUME”
control
for
35
watts
at
Left
and
Right
Channels
(16.7
volts
across
the
8-ohmloads).
Harmonic
Distortion
Analyzer
should
measure
0.5
%
distortion
or
less
at
each
channel.
CAUTION: This precision high-fidelity instrument should be serviced only by qualified
personnel, trained in the repair of transistor equipment and printed circuitry.