
Model 8640B
TM 9-4935-601-14-7&P
A10 Assembly Removal and Disassembly
SERVICE SHEET D
SERVICE SHEET E
A26 Assembly Disassembly Procedure
A26A2 and A26A4 Access
1. Place instrument right side up and remove top cover (see Service Sheet F).
2. Remove four pan-head screws (with lockwashers) that secure casting top cover to casting.
3. Lift cover from casting.
4. To service either A26A2 or A26A4, gently lift board's extractors and reinstall it on extender board.
5. Reassemble by reversing procedures in steps one through four.
A26A1 and A26A3 Access
1. Place instrument upside down and remove bottom cover (see Service Sheet F).
CAUTION
While working with and around the semi-rigid coaxial cables in the generator, do not bend the cables more
than necessary. Do not torque the RF connectors to more than 2 inch-pounds.
2. Remove ten pan-head screws (with lockwashers) that secure casting bottom cover to the casting.
WARNING
The RFI gasket on casting cover may have sharp edges and may cause personal injury if not handled with care.
3. Lift cover from casting, noting the orientation of the RFI gasket under the cover.
NOTE
Do not attempt to replace components on the A26A1 and A26A3 assemblies without removing them.
A26A1 and A26A2 Removal
4. Remove two pan-head screws (with washers) that secure microcircuit amplifier A26U1 or U2 to casting.
5. Remove A26U1 or U2.
6. Remove four pan-head screws (with lockwashers) that secure the heat sink to the casting.
7. Remove pan-head screws (with lockwashers) that secure the circuit board to the casting.
8. Disconnect two coaxial cables from casting connectors.
9. Remove nuts and washers that secure cable connectors to casting.
10. To replace components mounted on the circuit board, tilt the board up while sliding it to the rear.
11. To replace or remove the circuit board, label the wires soldered to the board before unsoldering them.
12. Reassemble by reversing procedures in steps one through 12.
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