Racal Instruments RA-117 User Manual page 47

(2) Unsolder the connecting wires from the two turret lugs situated in compartment
8, the leads to the turret lug in compartement 6, the pin connections compartment
2 and the screened cable compartment 1.
(3) Unscrew the three fixing screws on the top of the unit.
8.
(1) Fitting a new chain:-
(a) Take a 63-link lenght of chain.
(b) Hold chain tension sprocket down towards the chassis, and fit new chain
round the two chain wheels.
(c) Release the tension sprocket that ensuring that it holds the chain under
tension. See Front Panel instructions refitting of B.F.O. control knob; para.2.
above.
100 kc/s I.F. Amplifier
9.
(1) Remove the left-hand gusset plate adjacent to the unit.
(2) Unsolder the leads to the 4 and 12-way tag strips (fig.7) and the 100 KC/S
OUTPUT plugs.
(3) Disconnect the coaxial lead to the 1.7 Mc/s oscillator/ amplifier and mixer unit.
(4) Remove the six screws securing this unit to the main chassis.
NOTE: Removal of the R.F./I.F. GAIN control on the B.F.O. assembly is necessary in
order to obtain acces to one of the six securing screws.
(5) Re-assemble in the reverse order.
Beat Frequency Oscillator
10.
(1) Remove Front Panel.
(2) Remove bottom cover.
(3) Disconnect leads from R.F./I.F. GAIN potentiometer.
(4) Remove side plates adjacent to I.F. amplifier.
(5) Remove screw securing cable cleat situated adjacent to 150mH choke assembly
on underside of I.F. amplifier.
(6) Disconnect red-white lead of B.F.O. cableform from terminal on adjacent 12-way
tag strip.
(7) Withdraw red-white lead from cableform.
(8) Disconnect brown leads from pin 4 of V18 socket.
(9) Disconnect blue leads from pin 7 of V21 socket.
(10) Remove remaining three screws and crinckle washers to release B.F.O. assembly
from I.F. amplifier chassis.
(11) Re-assemble in the reverse order.
1.7 Mc/s Oscillator/Amplifier and Mixer Unit
11.
(1) Remove the bottom cover and the screen from compartment 7.
(2) Unsolder the two pin connections.
Dismantling 47