Table of Contents
Advertisement
3.3.2 DISTORTION/SINAD ALIGNMENT
1.
Select Generate
function and Gen/Mon Mtr dis-
play.
Using
an audio
generator
with less than
0.1
%
distortion,
apply a 900
mVrms,
1-kHz
±
2Hz sig-
nal
to the Vert/SINAD/DVM/Dist/Counter
input
port on the
front
panel.
2.
Verify
that the
distortion reading
on
the
CRT
is
..;;;;Q.5
%.
If this test
fails,
align the notch filter.
3.
Turn
the
System Analyzer OFF
and
extend the
Scope/
DVM
Control
board using the
100-pin
extender card.
4.
Turn the
System
Analyzer ON and
select
Gener-
ate
FM function and Gen/Mon Mtr display.
5.
Using the
same
low-distortion
generator
as in
step
1,
apply a
998
±
0.2-Hz
sinewave
to the distortion
input port (Dist
In).
6.
Alternately
adjust
the
998-Hz
notch
potentiome-
ters on
the
Scope/DVM
Control
board
(Figure
3-4)
to null
the
distortion reading
on
the
CRT.
You
should
get a reading of
less
than
0.5
%.
7. Change
the
audio generator's
input frequency
to
1002
±
0.2 Hz.
8.
Alternately adjust the 1002-Hz notch
potentiom-
eters on the Scope/DVM
Control
board
(Figure
3-4) to
again null
the
CRT distortion
reading.
You
should
again
get a
reading
of
less than 0.5
%.
9.
Turn the
system's
power OFF and put
the Scope/
DVM Control board back into the system
chassis.
3.3.3
RECEIVER
3.3.3.1
Unear IF
1.
Perform the basic alignment procedure of
para-
graph
3.2.
2.
Turn the
System
Analyzer OFF
and
remove the
Receiver board. Remove
the
Receiver board
cover
install the Receiver Test
Cover
on
the
board and
insert
the
Receiver board into
the
approp'riate
extender
card.
Place the Receiver and extender
assembly
in
the
Receiver board's
edge connector.
3.
Turn
the
Analyzer ON and
select
Monitor AM
function and
Distortion
display.
Set
the monitor
frequency
to
250
MHz,
the
RF
step attenuator
(Step)
to
0
dB,
the
IF bandwidth
switch (BW) to
Wide,
and the Receiver audio filter
to 300-Hz
HPFL and 3-kHz
LPFL.
4. Connect
the
external
signal
generator to
the
Antenna port
on the front panel.
Adjust
the
exter-
nal
generator
for an output level
of approximately
-
80
dBm and
a calibrated, 30
percent AM,
1-kHz
tone
at 250
MHz.
5.
Connect
the
Demod
Out
port
to
the distortion
input port
(Dist
In)
on the
front panel.
6.
Adjust
C307 and C320
(marked
on the
Receiver
Test Cover) for lowest distortion;
adjust the signal
strength of the
generator as
needed.
7.
Select
Narrowband
FM
mode.
8.
Adjust
the
external
generator for
an output level
of approximately -40
dBm and
a calibrated
3-kHz
FM,
1-kHz tone.
'
9.
Adjust
C327, C328
and
C320
(marked
on
the
Receiver
Test
Cover)
for
lowest
distortion.
3.3.3.2
AM/AGC Calibration
1.
Select
Monitor AM function and Gen/Mon Mtr
display.
Set
the monitor
frequency
to
250
MHz,
the
RF
step
attenuator
to 0
dB,
and the
BW
switch
to
Narrow.
2. Connect the external generator to the Antenna
port
on
the
front
panel. Adjust
the external
gen-
erator
for
an output
level
of
-
50
dBm and
a
cali-
brated 40
percent
AM at
250
MHz.
3.
Adjust
R359 (marked on the
Receiver
Test
Cover)
for
a
reading
of 40
%
±
5
%
on the CRT
AM dis-
play.
4.
Adjust
R398
for
the increase
RF
attenuator
set-
ting warning
to just
flash
on the
CRT.
5.
Repeat steps
3
and
4
once.
3.3.3.3 FM Calibration
1.
Select
Monitor FM
function and Gen/Mon
Mt
r
display.
Set
the
monitor
frequency
to 250
MHz,
the
RF
step attenuator to 0
dB, and
the
BW
switch
to
Wide.
2. Connect the
external
signal generator
to
the
Antenna
port
on
the
front
panel.
Adjust
the exter-
nal
generator for a center
frequency
of 250
MHz
at
an output
level
of approximately -30
dBm
and a
calibrated
40-kHz
FM.
3.
Adjust R421
(marked on the
Receiver
Test
Cover)
for a reading
of
40 kHz
± 2
kHz
on
the
CRT
FM
display.
3.3.3.4 Spectrum Analyzer
NOTE
Unless the factory alignment
has
been
disturbed
through
repair,
do
not re-align
the Spectrum
Ana-
lyzer except
for
offset adjustment
(R241B). Because
all
the adjust-
ments
interact,
re
-aligning
t
he
Spectrum
Analyzer is
difficult.
1.
Remove cover
from
receiver
board.
2.
Connec
t
a high
input
impedance
frequency
counter
to
pin
8
of U201 on
the
receiver board
(see
Figure
3-6).
3. Adjust
C236 on the
receiver board
(see
Figure
3-6)
for a
frequency
reading
of 10.24 MHz
±
100 Hz.
4.
Replace
receiver test
cover.
5.
Select
Monitor
function and the
Spect
Analyzer
display
on the
System
Analyzer.
Set
the monitor
3-8
Advertisement
Table of Contents
Troubleshooting
