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3.
Adjust
the Spectrum
Analyzer Centering
poten-
tiometer on
the Scope/DVM
Control
board
(Figure
3-4) so that t he spectral
line
on
the CRT is
cen-
tered about
the
center
graticule
line.
3.2.13 HORIZONTAL TIMEBASE
1.
Select
Generate FM function
and
Signaling
Sequence (Seq)
display.
Select
AlB
encode,
and
program Tone A for
20.0 Hz,
and Tone
B
for
19,999.9
Hz.
2.
Select
Modulation
display.
Set the
Oscilloscope
controls
for
a vertical
range
of 2.5
kHz/Div,
Auto
Trigger,
and
a
horizontal sweep rate
of
10
mSec/
Div.
Set the
horizontal
and
vertical vernier
con-
trols
to Cal.
3.
Set
the
Code Synthesizer for continuous (Cont)
Tone
A,
and
turn
up the Code
Synthesizer
level
control (Code
Synth
Lvl)
to
obtain
a
nearly
full-
scale
sinusoidal
waveform
on
the CRT.
Turn the
Ext Level and
the
1
KHz
Level
controls
OFF.
4. Adjust the Coarse Timebase Calibration poten-
tiometer on the Scope Amplifier board
(Figure
3-2) so
that
one
cycle
of the
displayed
waveform
occurs
in
5 em
along
the horizontal
axis. Use t
he
Vert and Horiz position
controls
to center and
move the
waveform;
this
will
measure the
5 em
in
the
middle of the
screen
and
avoid
nonlinearities
near the edge
of
the CRT.
5.
Set
the
Oscilloscope
Horiz
control for a
sweep
rate
of
10
11Sec/Div
and select
Tone
B
output on the
Code
Synthesizer.
6.
Adjust the
Fine Time
base
Calibration capacitor
on
the
Scope
Amplifier board (Figure
3-2)
so
that one
cycle
of the
displayed waveform occurs in
5 em
along the
horizontal
axis.
As
with coarse timebase
calibration, use
the Vert and
Horiz position
con-
trols to center and
move
the
waveform.
3.3
EXTENDED
ALIGNMENT PROCEDURE
3.3.1
DVM
Perform
3.1.2 preparation for alignment and 3.2
basic alignment procedure
before
proceeding
to
any
of
the
extended
alignment procedure.
3.3.1 .1 Peak Detector Zero
NOTE
Do not
attempt to make a peak
detector
alignment with any boards
on extender
cards.
The
Receiver
Board
(A8)
may
be removed to
make
access
to
adjustments.
3-6
1. Select generate
FM
Narrowband
function
and
turn
the code
synthesizer,
External
level
control,
and
1
KHz
level
control
OFF.
2.
Connect an external
DVM
to TP4 on
the
Scope/
DVM
Control
board
(see
Figure
3-4).
3.
Adjust
the
positive
detector
zero (R67) fo
r
a
DVM
reading ofO.OOO
±
0.0009
Vdc
at TP4.
4.
Connect the external
DVM
to
TP6
on
the
Scope/
DVM
Control
board.
5.
Adjust the
negative
detector zero (R78) for a
DVM
reading ofO.OOO
±
0.0009
Vdc
at
TP6.
3.3.1.2
DVM X0.1 Gain
1.
Select generate
FM
Narrowband function and
Gen/Mon
Mtr
display.
2. Connect
an external DVM
to test
point TP6
on the
Scope/DVM
Control
board
(see(Figure
3-4).
3.
Turn on
the
1
kHz
internal modulation
and
adjust
the level until
the voltage at TP6 reads 2.000 Vdc.
NOTE
Because the
internal DVM
is
con-
tinuously
multiplexed
through
nine
internal
voltage
points,
the micro-
processor must
be
halted
to
make
the DVM X0.1 Gain
adjustment
.
The microprocessor must be halted
on
the negative
detector
cycle.
A
number of
halt attempts may
have
to
be made.
4.
Connect a
DVM
to test
point
TP5
on the
Scope/
DVM control board.
·
5.
To
halt the
microprocessor short test
point TP6
on
the Processor board
to
ground. Once the
micro-
processor
has been
halted
measure
the
voltage
at
TP5.
The
voltage
should
be 0.2V,
approximately
X0.1
the voltage at
TP6.
If
the voltage
at
TP5
is
not
approximately
XO.l
the voltage
ofTP6 restart
and
halt the
microprocessor until
it
is.
6. Now
that
the
microprocessor
is halted
in
the
neg-
ative
detector position,
adjust R167 (See
Figure
3-4)
so that the voltage
reading
at TP5 is
equal
to
XO.l
the
voltage at TP6 to
four
significant figures.
(Example TP6
-
2.000
Vdc, TP5
=
0.2000 Vdc.)
3.3.1.3 DVM
NOTE
Do
not
attempt
to
make the
DVM
alignme nt with any
boards
on
extender
cards.
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Troubleshooting
