
Model 8640B
TM 9-4935-601-14-7&P
CHANGE 25
Page 5-2, paragraph 5-21:
Change paragraph e to read as follows:
e.
A9A1A2C6, C7 and C8
. If the A9A1A2 FM Gain Switch Board Assembly has been replaced or repaired,
measure the 3 dB bandwidth at A7TP3 with an oscilloscope on the following RF frequency ranges while
driving the FM INPUT connector with an external test oscillator. Change the corresponding capacitor, if
necessary, for best flatness (less than 3 dB down at 250 kHz rate). Increase capacitance to decrease
deviation (250 kHz rate).
FREQUENCY
PEAK DEVIATION
RANGE (MHz)
Range
Capacitor
512 - 1024
5 kHz
A9A1A2C8
256 - 512
5 kHz
A9A1A2C7
128- 256
5 kHz
A9A1A2C6
NOTE
Changing any capacitor will likely affect flatness on other ranges.
Page 5-2, Table 5-1:
Delete A9C8 (see Change 1).
Add the following:
Service
Range of
Basis of Selection
Component
Sheet
Values
A9A1A2C6
6
0 - 56 pF
A9A1A2C7
6
500 - 900 pF
See paragraph 5-21
A9A1A2C8
6
750 - 2000 pF
Page 6-17 and 6-18, Table 6-3:
Replace the entire A9 assembly parts list with the following list.
A9
----------------
PEAK DEVIATION AND RANGE SWITCH ASSEMBLY
A9A1
08640-60179
SWITCH ASSEMBLY
A9A1MP1
0380-0013
SPACER, 1.0 LONG
A9A1MP2
0380-0013
SPACER, 1.0 LONG
A9A1MP3
0510-0005
RING, RETAINER 1/4 DIA
A9A1MP4
0510-0005
RING, RETAINER 1/4 DIA
A9A1MP5
0510-0005
RING, RETAINER 1/4 DIA
A9A1MP6
0510-0015
RING, RETAINER EXT
A9A1MP7
0510-0052
RING, EXT 0.125 DIA
A9A1MP8
0510-0052
RING, EXT 0.125 DIA
A9A1MP9
1430-0759
GEAR, SPUR
A9A1MP10
1430-0772
GEAR, PLANET
A9A1MP11
1430-0772
GEAR, PLANET
A9A1MP12
1430-0773
GEAR, COMBINATION
A9A1MP13
1430-0774
GEAR, COMBINATION
A9A1MP14
1460-0019
SPRING, COMPRESSION
7-56
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