RA117 serial number N0489 (/cont)

The 1.7MHz module is easy to remove from the chassis, but not so easy to refurbish, owing to the cramped nature of it’s design. This is largely due to necessity. Although it is generally referred to as the 1.7MHz module (because it contains the 1.7MHz crystal oscillator), it also contains the second VFO amplifier as well as the third and fourth mixers! I was fully expecting to find a few horrors inside due to heat build-up in such a confined space. However, apart from the odd resistor going high, the contents of the box were in reasonable condition. Traps L300 and L301 are in a small sub-chassis adjacent to the 1.7MHz module and can be dealt with at the same time. Alternatively you might want to address this while working on the second mixer since the sub-chassis is held down by the

L300/301 sub assy.

1.7MHz Osc. Etc.

same screws which retain the second mixer tag-board. L300 and L301 are necessary for removing unwanted signal content from the output of the second mixer. L300/C300 removes the 37.5MHz content. L301/C301 removes any 6MHz content. This is explained in Section 2, Ch1 of the RA117 manual.

Anti-clock-wise from top left … It is first necessary to remove the divider screen. The small tag-board at the bottom of the picture is reminiscent in a small way of the board found in the second VFO in the RA17 and RA17L. Care should be exercised in relation to the fine wires associated with the two variable inductors. It might be seen as a good idea to test the oscillator prior to refitting the screen. Note also that L330 which is on the little tag-board cannot be accessed once the module is refitted to the chassis.


L302 (in conjunction with C308A) forms a 1.6MHz rejection filter. This is explained in para. 26 of the alignment procedure in the RA117 manual.


The 0.1uF capacitor just above the screen in the final photograph is across the heater line and is a new addition.