
Model 8640B
TM 9-4935-601-14-7&P
CHANGE 1
NOTE
See paragraph 7-58 for recommended instrument modification.
Page 5-2, Paragraph 5-21:
Add the following:
g.
A9C8 Selection.
If A9 has been changed, perform FM 3 dB BANDWIDTH TEST (4-38) to determine if the
FM Amplifier is peaking above specification in the 5 kHz PEAK DEVIATION range. If the FM Amplifier is
peaking excessively, increase the value of A9C8 until flatness of the amplifier is within specification.
Page 5-2, Table 5-1:
Add the following:
Service
Range of
Component
Sheet
Values
Basis of Selection
A9C8
6
240-310pF
See paragraph 5-21.
Page 6-17, Table 6-3:
Change A8A4R2 to 2100-3216 RESISTOR, VAR, TRMR, 10K OHM 20%SC.
Add A9C8 0140-0210 CAPACITOR, FXD, 270 PF ±+5% 300 WVDC.
Page 6-22, Table 6-3:
Add A10A2C53 0180-0197 CAPACITOR, FXD, 2.2UF +10% 20 VDC TA.
Page 6-23, Table 6-3:
Change A10A2R55 to 0698-0085 RESISTOR, FXD, 2.61K 1% .125W F TUBULAR.
Delete A10A2R56.
Change A10A2R58 to 06983454 RESISTOR, FXD, 215K 1% .125W F TUBULAR.
Service Sheet 6 (schematic):
Add A9C8 270 pF (with asterisk) parallel to R22, between R21 and ground.
Service Sheet 11 (schematic):
Add A10A2C53 (2.2pF) from U1 pin 3 to ground with the positive electrode at pin 3.
Change A10A2R55 to 2610.
Delete A10A2R56.
Change A10OA2R58 to 215K.
Service Sheet 11 (Principles of Operation):
Schmitt Trigger (A 10A2):
Delete R56 from second sentence.
CHANGE 2
NOTE
See paragraph 7-60 for recommended instrument modification.
Page 6-37, Table 6-3:
Change A26A4VR2 to read 1902-0184 DIODE, VREG, 16.2V VZ, 0.4W MAX.
Service Sheet 12 (schematic):
Change A26A4VR2 to 16.2V.
CHANGE 3
NOTE
See paragraphs 7-62 through 7-67 for recommended instrument modification.
Page 6-17, Table 6-3:
Change A8A4R1 to 2100-0647.
7-25
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