TM 11-6625-255-14/TO 33A113170-1
3 percent R.M.S. VOLTS.
The spectrum analyzer meter should indicate 80
t. Repeat the readjustments described in r a n d
3 percent R.M.S. VOLTS. If this reading is not
s above until the reading of 250*3 percent R.M.S.
obtained, adjust C20 until the meter indicates 80
VOLTS is obtained for both 10,000 and 100,000
3 percent R.M.S. VOLTS.
H z without further readjustment. If the proper
o. Repeat the adjustments described in m a n d
tolerance cannot be obtained for both frequencies,
n above until the reading of 803 percent R.M.S.
follow the procedure given in o above to find the
VOLTS is obtained for both 10,000 and 100,000
proper value for R78, but refer to r and s above in
H z without further readjustment. If the proper
place of m and n a b o v e .
tolerance cannot be obtained for both frequencies,
measure R77 and replace it with a lower value
7 1 7 . Adjustment o f P r e a m p l i f i e r - B r i d g e
resistor selected from table 7-5 below. Repeat m
A m p l i f i e r Gain
and n above. If the proper tolerance still cannot be
Adjust the amplifier gain as follows:
obtained, replace R77 with a higher value resistor
than the original one and repeat m and n a b o v e
connect it to the AF INPUT terminal. Connect a
until the proper tolerances are obtained.
vtvm across the AF INPUT terminal and adjust
the signal generator output for a 0-dB indication
Table 7-5. Values of Resistors
o n the vtvm.
Values used in
Resistor
individual sets (K)
b. Set the function switch to SET LEVEL.
82
R77
c. Remove V6 from its socket.
91
d. Set the signal INPUT control to MAX.
100
e. R e m o v e t h e v t v m f r o m t h e A F I N P U T
110
binding posts without disturbing the signal
120
10
generator connections. Connect the vtvm to pin 8
R78
11
of V4. The vtvm should indicate between -2 and
12
-1 dB. This indicates a total gain of 18 to 19 dB
82
R90
for the amplifier. I f the proper reading is not
100
o b t a i n e d , replace R90 to compensate for the
120
150
error. The selective values of R90 are listed in
180
220
NOTE
of different value until the proper vtvm reading is
A n alternate procedure for finding the
obtained. I f t h e p r o p e r r e a d i n g c a n n o t b e
value of R77 when the d e c a d e resistor
obtained, replace tubes V2, V3, and V4 and repeat
b o x is available is to d i s c o n n e c t and
the selective procedure for R90.
m e a s u r e R77, set the d e c a d e resistor
f. Set the function switch to METER.
box for this value, and substitute it in
g. Set the meter range switch to -20 DB.
place of R77; then follow the procedure
h. Connect the signal generator to the METER
given here.
binding posts and adjust the signal generator for
p. Set the meter range switch to 300 R.M.S.
1 0 0 Hz. Adjust the signal generator output so
VOLTS.
that a reading of exactly -20 dB is obtained on
q. Adjust the signal generator for 1,000 Hz.
t h e spectrum analyzer meter. For the following
t e s t s , do not disturb the level of the 100-HZ
Adjust the voltage output of the signal generator
signal.
to produce a reading of 250 R.M.S. VOLTS on the
i. Set the function switch to SET LEVEL.
spectrum analyzer meter. Record the reading on
the vtvm.
j. Set the meter range switch to 0 DB.
r. Adjust the signal generator for 10,000 Hz at
k. S e t t h e A F - R F s e l e c t o r s w i t c h t o A F
the same voltage output recorded in g above. The
(TS-723A/U).
spectrum analyzer meter should indicate 250 3
l. Set the signal INPUT control to MAX.
p e r c e n t R.M.S. VOLTS. If this reading is not
o b t a i n e d , adjust trimmer C23 until the meter
METER binding posts to the AF INPUT binding
indicates 250 3 percent R.M.S. VOLTS.
posts.
s. Adjust the signal generator for 100,000 Hz
n. Adjust SET LEVEL GAIN control R38, on
at the same voltage output recorded in g above.
top of the chassis, to produce a meter reading of
The spectrum analyzer meter should indicate 250
exactly 0 dB.
3 percent R.M.S. VOLTS. If this reading is not
o. Set the function switch to NOISE.
p. Set the meter range switch to +20 DB.
obtained, adjust C23 until the meter indicates 250
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