
Model 8640B
TM 9-4935-601-14-7&P
CHANGE 9 (Cont'd)
Service Sheet 20 (schematic):
Change the part number for A8A2U14 (at U14B) to 1820-0205 (see note).
Service Sheet 21 (schematic):
Change the part number for A8A2U14A to 1820-0205.
NOTE
IC 1820-0205 is the recommended replacement for A8A2U14
in instruments with serial number prefixes below 1405A.
Service Sheet G (internal view)
Delete A3A4R5 OFFSET 1
CHANGE 10
NOTE
See Paragraph 7-83 for recommended instrument modification.
Page 1-10, Table 1-1:
MODULATION CHARACTERISTICS:
General:
Change
Internal Modulation Sources: Optional
to read as follows:
"Frequency: Variable 20 Hz to 600 kHz +10% in 5 decade continuous bands plus fixed 400 Hz
and 1 kHz +3%."
Pages 4-44 and 4-45, paragraph 4-30:
SPECIFICATION:
Option 001:
2% to +3%.
Delete steps 2 and 3.
Add the following:
2.
The frequency counter should read 400 + 8 Hz on a standard instrument, 400 ± 12 Hz on an Option 001.
The voltmeter should read greater than 1 Vrms on a standard instrument, 3 Vrms on an Option 001.
Standard:
392
__________
408 Hz
1.0 Vrms
__________
Option 001: 388
__________
412 Hz
3.0 Vrms
__________
3.
Set MODULATION FREQUENCY to 1 kHz (fixed). The frequency counter should read 1000 ± 20 Hz on a
standard instrument, 1000 + 30 Hz on an Option 001, and the voltmeter should read as specified above.
Standard:
980
__________
1020 Hz
1.0 Vrms
__________
Option 001: 970
__________
1030 Hz
3.0 Vrms
__________
Page 4-81, Table 4-1:
Change
4-30, Internal Modulation Oscillator Test
as follows:
400 Hz Fixed: Standard:
392
_______
408 Hz
1.0 Vrms
_______
Option 001: 388
_______
412 Hz
3.0 Vrms
_______
1 kHz Fixed: Standard:
980
_______
1020 Hz
1.0 Vrms
_______
Option 001: 970
_______
1030 Hz
3.0 Vrms
_______
7-30
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