Yamaha SPX990 Service Manual page 27

SPX990
ADJUSTMENTS
1.
Preparation
1-1 Preparation of the
Main
Unit
(1}
Input
levei
MAX
(both
L,R)
(2)
Level switching switch
...
-1-4
dB
side
(3)
MIDI
switch
OUT
side
(4)
A
600
ohms
load
resistor to the
2
pin
and
3 pin of
the
OUTPUT
XLR
(L,R)
terminals.
1-2 Preparation of the
Measuring
Instrument
(1)
The
distortion
measuring Instrument uses an 80
kHz, -6
dB/oct
filter
(2)
When
measuring
the noise
level,
a 12.7 kHz, -6
dB/oct
filter is
used.
(3)
The
output
impedance
of the
oscillator
is
600
ohms
or
less.
(4)
The
input
impedance
of the
measuring
instrument
is
1
megohm
or
less.
2.
Gain
When
a
1
kHz, -10
dBm
signal
is
added from INPUT
L,R,
the
OUTPUT
L,R level
is
within 0
±
10
dBm
Moreover,
when
the level switching switch
is
set to the
-20dB
side
for
both the input
and
output,
and
the input
level
is
set to -20
dBm.
the
OUTPUT
L,R
level
is
within
-10
±
1
dBm,,
After inspection, the
level
switching switch
is
returned
to
the
-f-4
dBm
side for
both
the input
and
the output.
3.
Frequency response
When
a
-10
dBm
signal
is
input
from
INPUT
L,R,
the
OUTPUT
L,R
frequency response
Is
set within the
ranges
in
the following
table,
with
1
kHz
as the standard.
20
Hz-20
kHz
±0.5 dB
24 kHz
-10
dB
or
less
1
.
Muting
Circuit
The mute
release time
when
the
power
is
turned from
off to
on
Is
3
seconds
±
1
second
When
the
power
is
turned from on
to
off,
there
is
no
click
noise or other
noise.
8.
Source Voltage Check
Checks
that the source voltage
is
within the following
ranges:
-fBV
±
0.2V, -^15V
±
0.6V,
-15V
±
0
6V
9.
Level
Meter Check
When
the output
level
is
set to
+19
dBm,
ail
of
the
level
meter LEDs
light
The
clipper
goes
out
at
an output
level
of
+16 dBm, and
the
LEDs go
out
in
succession from
the top each time
the Input
level
drops by
-6 dB.
10.
Adjustment
10-1 Clipping Level Adjustment
Turn VR102,202
fully to the
left.
When
1
kHz,
+8
dBm
is
input
from
the L-ch input
UK101), VR101
is
adjusted so
that the output
wave
form
of
the L-ch
output (JK103)
is
just before
clipping.
VR201
is
adjusted
in
the
same way
for
R-ch.
10-2
Gain Adjustment
Under
the conditions
in 10-1,
VR102
is
adjusted so
that the L-ch output
waveform becomes
+18.0
dBm
±
0.3
dBm
VR202
is
adjusted
in
the
same way
for
R-ch.
In
the
same
way,
input signals
from JK
102,202,
and
confirm
that signals are
output from
JK
104,204
at
the
same
level.
4.
Distortion
When
a -1 kHz,
+7
5
dBm
signal
is
added from INPUT
L.
R,
the
OUTPUT
L,R distortion
is
within
0.005%.
5.
Maximum
Output
When
a
1
kHz
signal
has been
input
to
INPUT
L,R
and
has
gradually increased,
a
+18.0
dBm
signal
is
obtained
at
OUTPUT
L,R within
a
distortion of
3%
Also,
when
a
signal
is
added
to
INPUT
R only, the
OUTPUT
L output signal
becomes
-50
dBm
or
less.
For
OUTPUT
R
as well, the
same
results are
obtained
6.
Noise
Level
The
output noise
level
is
-82
dBm
or
less
when
there
Is a
short
at 2
pin-3
pin of
INPUT XLR
L,R
at
150 ohms.
34