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TM 9-254
3-13.
Using Expendables - Continued
(1)
Silicone compound is used as an insulator and heat dissipator when replacing surface mounting
transistors (1) in electrical circuits.
(2)
Remove two hex nuts (5), two insulators (6), and two machine screws (2) from the chassis (3). Remove
transistor (1) and mica washer (7) from the chassis.
(3)
Clean the mounting surface of chassis (3) with alcohol and a brush or a clean cloth.
(4)
Spread a thin even coating to the bottom surface of the replacement transistor (1) and to both sides of
the replacement mica washer (7).
KEY to figure 3-42:
1.
Transistor
5.
Nut, hex (2)
2.
Screw, machine (2)
6.
Insulator (2)
3.
Chassis
7.
Washer, mica
4.
Leads, transistor
Figure 3-42. Applying Insulating Compound on a Transistor
(5)
Position the mica washer (7) on the bottom of the replacement transistor (1) with the leads of the
transistor protruding through the two holes in the center of the mica washer.
(6)
Aline the mounting holes in the mica washer (7) with the mounting holes in the replacement transistor (1)
and insert two machine screws (2).
(7)
Aline the two machine screws (2) and the two leads (4) of the replacement transistor (1) with the holes in
the chassis (3) and press in place.
(8)
Position two insulators (6) and install two hex nuts (5) onto the two machine screws (2) and tighten
securely.
(9)
Use a clean, dry cloth to wipe off any excess silicone compound from around the base of the transistor.
g.
Heat Shrinkable Sleeving (fig. 3-43). Heat shrinkable sleeving is used to cover solder joints on variable
resistor terminals, relay terminals, switch terminals, transformer terminals, and connector pins. A general procedure for
installing heat shrinkable sleeving is described below:
3-40
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