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Dismantling
46
(3) Hold the two gear wheels at the top of the right-hand film bobbin against the
spring tension and remove the two screws securing the idler gear mounting as-
sembly.
(4) Ease the idler gear clear of the film bobbin gear wheels and carefully ease the
spring tension from them. The film bobbins are then free to revolve independently.
(5) Carefully lift the film clear of the tuning drive sprocket and withdraw the film
via the back of the loudspeaker.
Fitting a New Film Scale
5.
(1) Carefully feed the low frequency end of the film scale via the rear of the loud-
speaker, the front of the tuning drive sprocket and the front of the guide roller
mounted between the two right-hand film bobbins. Engage the prepared end of
the film in the right-hand bobbin. Slowly wind the film, under very light tension,
onto the bobbin until the STOP marking is approximately in the centre of the
escutcheon window.
(2) Carefully feed the free end of the film via the rear of the loudspeaker and the rear
of the tuning drive sprocket. Engage the prepared ond of the film in the left-hand
film bobbin. Slowly wind the film, under very light tension, onto the bobbin until
the sprocket holders in the film engage with the tuning drive sprocket.
(3) Maintain the STOP marking approximately in the centre of the escutcheon win-
dow and take up any slack in the film by rotating the bobbins in opposite di-
rections. When all the slack has been taken up, rotate the gear wheels on top of
the bobbins a further 1/2 to 3/4 turn against the spring tension and hold them
in position. Refit the idler gear wheel and mounting plate. Secure the mounting
plate screws and release the gear wheels.
(4) Check that the STOP marking is still approximately in the centre of the es-
cutcheon window.
Second V.F.O. Variable Capacitor
NOTE: Refer to the v.f.o. alignment procedure in para. 24. before attempting to refit
the variable capacitor.
6.
(1) Remove the second v.f.o. from the receiver in accordance with the instructions in
para.3. above.
(2) Unscrew the remaining cover plate.
(3) Unsolder the capacitor connections.
(4) Remove the drive gear and collet.
(5) Unscrew the four fixing screws holding the capacitor to the bracket.
(6) Re-assemble in the receiver order, ensuring that the anti- backlash gears are
loaded.
First Variable Frequency Oscillator
7.
(1) Remove the front panel, the bottom cover and the screens from compartments 1,
6 and 8. (See Fig.15: Key to Under- chassis Layout).
Summary of Contents for RA-117
Page 1: ...Racal RA 117 Radio Receiver...
Page 24: ...Detailed Circuit Description 24 at maximum is the correct calibration maintained...
Page 32: ...32...
Page 70: ...Illustrations 70...
Page 71: ...Illustrations 71...
Page 72: ...Illustrations 72...
Page 73: ...Illustrations 73...
Page 74: ...Illustrations 74...
Page 75: ...Illustrations 75...
Page 76: ...Illustrations 76...
Page 77: ...Illustrations 77...
Page 78: ...Illustrations 78...
Page 79: ...Illustrations 79...
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Page 81: ...Illustrations 81...