
TM 9-4935-601-14-7&P
Model 8640B
SERVICE SHEET B (Cont'd)
12. Unsolder five wires from feedthroughs to left of A8A1
Assembly. Remove A8A1.
A8A3 Removal
13. On bottom of A8 Assembly casting, under A8A3 Assembly,
remove hex nut and lockwasher that secure A8A3J1.
14. Unsolder five wires from feedthroughs to right of A8A3
Assembly.
15. Remove two board supports and pan-head screw (with
lockwashers). Remove A8A3.
Reassembly
16. Reassemble and reinstall A8 Assembly be reversing the procedures in
steps one through 15.
NOTES
1. When replacing the casting top cover be sure that the
prongs on the brass RFI shield are behind the casting
wall.
2. The button shield must be carefully aligned to be sure
that the buttons do not catch on the edges of the
holes. Check the action of all the COUNTER MODE
buttons when the window is replaced.
SERVICE SHEET B (Cont'd)
A8 Counter/Lock Assembly Legend
Item Number
Reference
Designator
Description
1
A8FL1-4
Feed Thru Filter
2
A8C1-4
Feed Thru Capacitor
3
A8C5,6
Feed Thru Capacitor
4
A8MP1
Bushing Insulator (Nylon)
5
A8U1-6
Numeric Display
6
A8MP2
Lockwasher
7
A8MP3
Mica Washer
8
A8MP4
Center Filter Gasket
9
A8MP5
Center Scaler Gasket
10
A8L1-5
Inductor
12
A8MP6
LED/Button Shield
13
A8MP7
Center Filter Cover
14
A8MP8
Large Frame (RF Shield)
15
A8MP9
Small Frame (RF Shield)
16
A8MP10
Center Input Cover Shield
17
A8 MP11
Heat Sink
18
A8MP12
Counter Window
19
A8MP13
P.C. Board Support
20
A8MP14
Button Shield
21
A8MP15
Top Casting Cover
22
A8MP16
Bottom Casting
23
A8MP17
Light Pipe
25
A8MP18
Light Pipe
26
A8A4
Counter/Display Assembly
27
A8A3
Time Base Assembly
28
A8A2
Counter/Lock Assembly
29
A8A5
Counter Riser Board
30
A8A1
R.F. Scaler Assembly
31
A8MP19
X10 Button
32
A8MP20
X100 Button
33
A8MP21
ON Button
34
A8MP22
INT Button
35
A8MP23
EXT Button
36
A8MP24
Flat Washer
37
A8MP25
Lockwasher
38
A8MP26
Machine Screw
39
A8MP27
Machine Screw
40
A8MP28
Machine Screw
41
A8MP29
Lockwasher
42
A8MP30
Hex Nut
43
A8MP31
Flat Head Screw
44
A8MP32
Counter Insulator
45
A8MP33
Machine Screw
46
A8MP34
Machine Screw
47
A8MP35
Lockwasher
48
A8MP36
Machine Screw
50
A8MP37
Machine Screw
51
A8MP38
Machine Screw
52
A8MP39
Blind Dome Rivet
Figure 8-77. A8 Counter/Lock Assembly Illustrates Parts Breakdown
8-73
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