HP 8559A Operation And Service Manual page 291

SERVICE
Rear Drive Hub (15) on Bandwidth Shaft (55) is preset flush with collar on
shaft (see Figure 8-7B). Do not remove drive hub unless necessary for repair.
e. Use a no. 4 hex wrench to loosen the two screws on Coupling Hub (54) attached to Frequency Span
Shaft (9), and remove hub from shaft.
f. Remove the two Studs (53) used to support Bandwidth Switch Board (59). Remove Bandwidth
Detent (52) from Front Switch Assembly.
20. Remove the remaining Screws (48) attaching Front Switch Board Assembly M A 1 to Front Switch Diecast
21. Twist the left side of Front Switch Board Assembly M A 1 down approximately l/&inch to provide clear-
ance from Front Switch Diecast support arm (upper left corner). Lift Front Switch Board Assembly A2A1
from Front Switch Diecast (1) and set aside.
22. Removal of Rotor Assemblies:
Remove Attenuator Drive Rotor (8), front Anticrush Drive Hub Assembly (7), and Attenuator Shaft
a.
Assembly (18) from Front Switch Diecast (I), and set these parts aside.
b. Remove Frequency Span Rotor (14) with associated parts (9
Drive Hub (15) on Frequency Span Shaft (9) is preset at 12.954 mm (0.510 in.)
from end of shaft (see Figure 8-7C). Do not remove drive hub from shaft
unless necessary for repair.
c. Remove both remaining rotor assemblies from Front Switch Diecast (I), and set aside. Be careful to
keep Ball Bearings (10) and Springs (1 1) with their respective rotors.
Press Locking Link (5) into Front Switch Diecast (I) to release pressure on Dowel Pin (4). Remove
a.
Dowel Pin through cutout in Front Switch Diecast. (Individual parts are identified in Figure 8-9.)
b. Remove Locking Link ( 9 , Locking Shaft (3), and Lock Spring (2) from Front Switch Diecast.
CLEANING AND INSPECTION OF FRONT SWITCH ASSEMBLY
1. All switch contacts must be totally clean and grease-free for proper operation. Use a 50-50 mixture of
isopropyl alcohol and distilled water to thoroughly clean switch rotor contacts and Front Switch Board
Assembly A2A1. Avoid touching contacts with fingers.
2. Inspect for bent or damaged shafts, worn or broken contacts, weak or broken springs, rough feeling
potentiometers, cracked castings, and damaged PC boards. Check for signs of corrosion or rust. Replace
any suspect parts.
3. A special Instrument Grease (HP Part Number 6040-0584) is recommended exclusively for use during
switch reassembly. Lubrication is essential for proper operation of switches and lock. A small brush is
recommended for applying the Instrument Grease.
8-28
NOTE
12, 15
- -
NOTE
MODEL 8559A
17) from Front Switch Diecast