Control Unit

TM 11-5821-277-20

unit replacement; push the plug firmly into con-

(1) Note or mark the position of the front

nector J1 and turn the outer shell to lock it in

k n o b which is to be removed in relation to the

place.

f r o n t panel of the control unit.

e. Insert the control unit into its mounting

(2) Loosen the two setscrews that secure the

slot.

knob to the mounting shaft.

f. Hold the control unit in place and turn

( 3 ) Slide the knob off the mounting shaft.

the four quick release fasteners to secure the con-

I f the front knob is to be replaced, proceed to

trol unit to the instrument panel.

(9) below. If a rear knob is to be replaced pro-

g. P e r f o r m t h e p e r f o r m a n c e checks given

ceed to (4) below'.

in paragraph 4 5 to insure that the radio set is

(4) Note the position of the rear control

operational.

knob.

(5) Loosen the two setscrews that secure the

r e a r knob to the mounting shaft.

4 - 1 7 . Transceiver

( 6 ) Slide the knob off the shaft and slide

WARNING

the new knob) into place; be sure that, the phy-

Be sure that the 27.5volt dc circuit

s i c a l orientation is the same as that of the re-

breaker that supplies power to the radio

moved knob.

( 7 ) N o t e t h a t s u f f i c i e n t clearance exists

set is deenergized before performing the

between the rear of the knob and the front panel

procedures given below.

of the control unit to prevent binding when the

a. Removal.

knob is rotated.

(1) If safety wire is used to sexure the

(8) Hold the knob in place and tighten the

h o l d d o w n clamps that secure the transceiver in

t w o screws that secure the knob to the shaft.

the mounting, note how the safety wire is af-

(9) Insert either a new knob or the knob re-

fixed and remove from the holddown clamps.

m o v e d in (3) above on the mounting shaft; be

(2) Loosen the two nuts (fig. 1-6) that

s u r e that phtsical orientation is the same as

s e c u r e the holddown clamps in the place over

the removed knob.

t h e holddown brackets on the transceiver and

( 1 0 ) Tighten the two setscrews that secure

s l i d e the holddown clamps off the holddown

the knob to the mounting shaft.

brackets.

(11) Rotate the knob to be sure that it does

( 3 ) Grasp the handle on the front panel of

not bind or drag against the rear knob.

t h e transceiver and carefully pull straight for-

ward to disengage the mating connecters on the

4-16. Control Unit

t r a n s c e i v e r and mounting (fig. 1-5).

WARNING

(4) Slide the transceiver forward out of the

mounting.

B e sure that the aircraft master power

b. Replacement.

swithch is off and the 27-volt dc circuit

(1) Place the transceiver between the mount-

breaker that supplies power to the radio

ing guide rails and push the transceiver straight

set is deenergized before performing the

i n t o the mounting until the mating connectors

procedures given below.

just touch.

CAUTION

( 2 ) Check to see that the locating pins on

t h e mounting (fig.1-1) mate properly with the

Be careful not to plaice undue strain on

transceiver.

t h e aircraft cabling while performing

(3) Firmly push the transceiver straight

the procedures.

back to insure a secure mating of the connectors

a. Loosen the four quick-release fasteners (fig.

on the mounting and the transceiver.

1 - 1 ) that secure the control unit to the aircraft

( 4 ) Place the holddown clamps in place

o v e r the holddown brackets on the transceiver

instrument panel (or other applicable mounting).

b. Pull the control unit straight out of its

a n d tighten the nuts that secure the holddown

m o u n t i n g until connector J1 at the rear of the

Clamps.

unit can be reached.

(5) If safety wire was removed in (1) above,

c. Disconnect the aircraft wiring harness plug

replace the safety wire.

from connector J1 at the rear of the control unit.

( 6 ) Perfrom the performance checks out-

d. Carefully mate the aircraft wiring harness

lined in paragraph 4-5 to be sure that the radio

plug with connector J1 at the rear of the control

set is operational.

4-10