Fisher CA-77 - Page 5

RECOMMENDED
TEST
EQUIPMENTS
The
following
test
equipments
are
recommended
to
completely
test
and
align
the
Amplifier:
@
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.
-ONTROL
SETTINGS:
ONE
CHANNEL
DRIVEN:
Jnplug
the
AC
power
cord
and
set
the
front
panel
1)
Connect
a
low
distortion
audio
generator
to
LEFT
ontrols
as
follows:
AUX
IN
jack.
Set
generator
frequency
to
1
kHz
»
GRAPHIC
EQUALIZER
and
BALANCE
controls
to
and
output
to
minimum.
center
positions.
:
Q
2)
Connect
an
8ohm
load
resistor
between
-
POWER
switch
to
OFF
SPEAKERS
SYSTEM-A
LEFT
and
COM
terminals.
Connect
a
Harmonic
Distortion
Analyzer
and
an
.
SPEAKERS
switch
to
SYSTEM-B
AC
VTVM
in
parallel
across
the
8-ohm
load.
-
FUNCTION
switch
to
AUX
3)
Connect
the
AC
power
cord
and
set
SPEAKERS
Seance
switch
to
SYSTEM-A.
Turn
VOLUME
control
to
_
TAPE
MONITOR
switch
to
SOURCE
MAX
-
LOUDNESS
switch
to
OFF
4)
Increase
generator
output
for
50
Watts
RMS
eeeaee
(20.0
V
across
the
8-ohm
load).
Harmonic
HI
FILTER
switch
to
OFF
Distortion
Analyzer
should
measure
0.2%
distortion or less.
VOLUME control to MINIMUM positi
Se
a
Peta
5)
Repeat
steps
1
through
4
for
RIGHT
CHANNEL.
LEFT CHANNEL DRIVEN
BOTH CHANNELS DRIVEN
Connect
8-ohm
load
resistors
across
LEFT
and
RIGHT
SPEAKERS
SYSTEM-A
terminals.
Adjust
generator
output
and
“BALANCE”
control
for
50
Watts
at
Left
and
Right
Channels
(20.0
volts
across
the
8-ohm
loads).
Harmonic
Distortion
Analyzer
should
measure
0.2%
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.