General Removal and Replacement Procedures

TM 11-5820-509-35

generation sections of the equipment, always adjust the

(2) Before removing Signal Data Translator

replacement component lead length, component

CV-1377A/PRC-47 (A8A3) or Oscillator Control C-

placement, and proximity to adjacent devices as nearly

4311/PRC-47 (A8A7) adjust the front panel frequency

as possible to the original installation. This minimizes

control knobs to provide a reading of 2000 on the

the final alignment adjustments for the stage.

KILOCYCLES indicator. This places the shaft couplers

of these modules in the proper position to facilitate

module removal from the main chassis.

(4) High power semiconductor devices are

(3) When servicing the driver tube (A3V3)

often mounted on heat sinks. Whenever a device is

and the power amplifier tube (V101), remove the tube

replaced, always replace the insulating washer(s) if they

and its heat sink as a unit from the subassembly.

have been used in the original installation.

Carefully observe the orientation of these tubes in their

heat sink before separating them; installation of the

CAUTION

replacement tube is easier if the heat sink is properly

Before installing insulating washers,

oriented outside the subassembly.

treat them with silicone fluid or

(4) Disassemble only those items and

compound to enhance the heat

component subassemblies that are required to perform

conductivity through the washer.

the desired maintenance. Any defective part that

Check the continuity between the

cannot be repaired should be replaced.

semiconductor case and the heat

(5) Soldering must be in accordance with

sink before making other electrical

Military Specification MIL-S-6872. Use only rosin-core

connections to the replacement

solder. A wire solder containing 60-percent tin and 40-

device.

percent lead, having a diameter of l/16-inch and

meeting the general requirements of this specification is

(5) When replacing ceramic or glass

available in one-pound quantities under Federal Stock

components, use a heat sink and avoid excessive

Number 3439-753-1874.

pressure when gripping the component or its leads

(6) Clean all parts after soldering to remove

during soldering and attachment.

residual rosin. Denatured alcohol (FSN 6810-222-2373)

(6) Subminiature tubes are wired directly into

is recommended for this purpose.

the subassemblies: apply heat to these electrode leads

(7) Replacement wiring should be the same

carefully to avoid damage to the tube envelope

length and gage as the wire it replaces and should be

(7) Avoid overheating the capacitor body

dressed to conform to the routing of the original

when replacing ceramic feed-through capacitors in a

conductor.

chassis. The plating can be destroyed by excessive

(8) Remove a defective part from a printed

heat.

circuit card by clipping its leads as close to the terminal

(8) When tightening the setscrews in a collar-

hole as possible.

type clamp, the setscrews must be tightened against the

(9) Clear the terminal hole of a printed circuit

center of the mechanical part.

card by applying only enough heat to cause the solder to

(9) Special care must be exercised when

flow; then clear the solder and clipped component lead

soldering the terminal posts of some variable capacitors.

out of the terminal hole with a small pick.

Excessive heat can loosen the stator plates of some

(10) Insert the lead wire(s) of the replacement

assemblies.

component into the terminal holes of the printed circuit

card and adjust their individual lengths and dress to

3-9. General Removal and Replacement Procedures

locate the replacement component in the same position

as the original one (use parts location photographs to

a. These general procedures are in addition to the

verify the location of this replacement part). Solder the

specific routines listed in section V and are intended to

leads using a heat sink; then clip off the excess lead

act as guidelines to assist the maintenance technician in

wire.

the removal and re placement of components in

assemblies of Radio Receiver-Transmitter RT-671

c. Printed circuit card repair is not recommended

/PRC-47.

unless the repair is minor The following procedures are

b. Whenever component parts are removed for

recommended when such repair is desired.

repairs, adjustments, or internal measurements:

(1) Eliminate the progress of a crack in the

(1) Remove all power from the equipment,

circuit card by drilling a stop hole (no. 65 drill) at the

and ground the high-voltage circuits at chassis

end of the crack.

connectors J1-A1 and J1-A2.

(2) If a Crack extends under or through the

3-96