Power Amplifier (A8A4A1) Plate Capacitor Switch Assembly

TM 11-5820-509-35

5/16 flat head screws (104) and (106) and release

3-17. Power Amplifier (A8A4A1) Plate Capacitor

bracket (86) from the side of power amplifier

Switch Assembly

compartment (111).

(fig. 3-91)

(11) Carefully remove the switch assembly

through the top of the power amplifier compartment.

a. Disassembly Procedures.

Disassemble the

power amplifier plate capacitor switch assembly only to

(12) Disassemble the rear switch wafer-bracket

the extent necessary to accomplish the needed repair.

assembly as follows:

(1) Remove the top and bottom covers from

(a) Unsolder

insulated

bus

wire

the power amplifier compartment by removing the 4-40

attached to solder lug (69).

x 1/4 screws that secure these covers in place.

(b) Remove 6-32 x 3/8 pan head

(2) Remove the front panel covers to which

screws (87) and (103) with washers (86) and (102) that

the POWER AMPLIFIER LOAD-TUNE chart is attached

secure bracket (85) to sleeve nuts (46) and (72).

by removing the four 6-32 x 3/8 flat head screws that

secure it in place.

and fiber washers (45) and (71) from studs (13) and

(16); withdraw rear switch wafer (26) and bracket

CAUTION

assembly (85) as a unit.

Exercise extreme care not to damage

(d) To remove the capacitors from

the rubber gasket that is used with

bracket (85), carefully remove solder lugs (43), (49),

the POWER AMPLIFIER LOAD-TUNE

(53), (57), (61), (65) and/or (69) from capacitors (44),

chart cover.

(50), (54), (58), (62), (66), and/or (70); then remove 6-32

x I/4 pan head screws (89), (91), (93), (95), (97), (99),

(3) Rotate the megahertz frequency-control

and/or (101) with associated washers.

shaft from the front panel to gain access to the

(13) Disassemble the front switch wafer-

setscrews of shaft collar (10). Loosen setscrews (9).

capacitor plate assembly as follows:

(4) Carefully withdraw fiber switch shaft 12)

(a) Withdraw sleeve nuts (5) and (11)

from the switch assembly through the access opening in

from the heat deflector end of the switch assembly

the front panel, and remove shaft collar (10), spur gear

without removing studs (13) and (16).

(8), and washer (7) as it is withdrawn. If sleeve bearing

(6) is loose in its housing, remove this part to prevent

NOTE

loss.

Exercise extremes in removing the

(5) Unsolder the insulated bus wire attached

studs to assure that sleeve spacers

to capacitor (82); tag this bus wire.

(14), (17), (21), and (24) and fiber

washers (15), (18), (20), (22), (23), and

NOTE

(25) are not lost.

This lead connects the rotor of

switch wafer (19) with the large

(b) To remove the capacitors from plate (73)

transmitting-type capacitor (C122)

carefully unsolder the capacitor pigtail before removing

mounted on the rear wall of the

the attaching hardware. The 3-48 x 3/16 pan head

power amplifier compartment.

screws (28), (30), (32), (34), (36), (38), and (40) with

washers (27), (29), (31), (33), (35), (37), and (39) secure

(6) Unsolder the shielded lead at the junction

capacitors (78) through (84) to capacitor plate (73).

of capacitors (76) and (77). Loosen screw (301 and

b. Repair Procedures.

remove the shield and solder lug (29A) Install screw (30)

and washer (29) and tag the shield.

(1) Examine all parts of the disassembled

(7) Unsolder the insulated bus wire attached

power amplifier plate capacitor switch assembly for

to the TUNE inductor spring contact assembly. This

damage or excessive wear. Particular attention should

connection is directly behind the POWER AMPLIFIER

be directed to the panel sleeve bearing, drive gear

TUNE control knob and is accessible from the bottom of

teeth, switch contact fingers, and ceramic switch parts.

the power amplifier compartment; tag this wire.

Replace any component or part that is defective.

(8) Remove the power amplifier tube access

(2) Do not lubricate any gear, sleeve bearing,

cover from the front of RT-671/PRC-47 by removing the

or switch contact in this assembly. Damage to other

four 8-32 x 1/2 flat head screws. Carefully remove the

plate circuit components or circuit malfunction can occur

plate cap from this tube.

if lubricants are used.

(9) Remove the two 6-32 x 1/2 flat head

(3) Examine the rubber gasket used in

screws (1) and (3) that secure the plate capacitor switch

conjunction with the access cover; replace this gasket if

assembly to the front panel.

it is grossly deformed or broken.

(10) Loosen and remove hex nuts (107) and

(108) with washers (106) and (109); withdraw two 4-40 x

3-111