Agilent Technologies 8640b User manual

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
DESCRIPTION
• A9, Peak De iation and Range Switch Assembly
A9 REMOVAL AND DISASSEMBLY PROCEDURE
1. Set PEAK DEV AT ON and RANGE switches fully ccw.
2. Remove PEAK DEV AT ON and RANGE switch knobs. The knobs are secure
with allen screws in the knobs.
3. Place instrument upside down and remove bottom cover (see Service Sheet
G).

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
4. Remove two nuts that secure A9 Assembly to front panel (located at switch
bushings).

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
5. Remove connectors A9A1P1 and A9A2P1 from jacks on A13 Assembly. Lift
rear of A9 Assembly until coupler slides apart. Gently slide the assembly back
and up to remove. Re-install assembly by setting both switch shafts fully ccw
and reversing the procedures in steps one through six. f Option 003 is
installed, remove both cables from the Reverse Power Assembly.
NOTE
The detents of both A9 Assembly and AlO Assembly switches must
align and
correspond to the same positions. Check that the actual RF output
frequency
agrees with the counter indication on all ranges. Refer to paragraph 5-
29.)

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
A9A1 and A9A2 Remo al
NOTE
For the following steps, orient the switch assembly with A9A1W1 and
A9A2W1 up.
Numbers in parentheses refer to items in the accompanying illustrated
parts breakdown.
6. Set both shafts fully ccw, and desolder the three wires attached to the
potentiometer terminals.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
7. Remove retainer ring (49) at front of potentiometer shaft, and slide
potentiometer and its mounting plate out to the rear of the switch.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
8. Remove retainer ring (1), washer (25), spring (24), and 4-contact rotor (23)
at rear of switch.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
9. Remove two machine screws with lock and >at washers (31, 34, and 35) at
right rear of switch. Remove two machine screws (2 and 8) and accompanying
spacers (18) located at front left of switch.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
10. Slide A9A2 Assembly (36) and gear mounting plate (37) o? of detent
shafts.
11. Slide T-shaft (17) with its accompanying combination gear (19) and planet
gears (15 and 42) o? of solid shaft (part of 50).

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
12. Loosen setscrews and remove combination gear (13) from solid shaft.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
13. Loosen setscrews and remove spur gear (40) from hollow shaft (part of
47).
Steps 14 and 15 may be skipped at this point, if you are only replacing the
gearset. You have full access to the gears without further action...
14. Remove two machine screws (46) at front right of detent mounting plate
(4), and remove P.C. board support (41).
15. Slide A9A1 Assembly (11) o? of detent shafts.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
A9 Reassembly
16. Reassemble A9 Assembly by reversing steps 6 through 15 above, while
observing the following points:
a. f the shaft index assemblies (47 and 50) were removed, mount them
with the index tab pointing to the top of the switch. Mount the hollow
shaft on the right side. When assembly is complete, check to be sure
the shafts do not bind against the P.C. boards. f the shafts bind, loosen
mounting screws (48) to adjust.
Gearset Replacement Steps:
Install the new brass combo gear and spur gear.
Install the new brass combo gear and planet gears onto the T-Shaft by
removing the retainer clips from the planet gears replacing the gears and
reinstalling the retainer clips.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
b. Set detent shafts fully ccw.
c. nstall both the 3-contact rotor (9) and the 2-contact rotor (43) with
contacts aligned vertically and toward the bottom of the switch.

Adapted from HP Service Sheet “D” WB0SMX
8640b Gear Set Replacement
d. Set the rear, 4-contact rotor with contacts aligned vertically and
pointing toward the top of the switch. This adjustment is made by
loosening the set screws on the combination gear (13) to reset the rotor
position.
e. FM Deviation and Counter lights must be vertical after A9 is
reassembled.