The Repair and restoration of another early Racal RA17 . . .
The 2nd VFO unit in this particular RA17 was not the hot bed of nasties that my one was. However the tubular capacitors on the small tag board were extremely discoloured and electrically unsound. 33% of the resistors in this unit were high in value by over 33% and two merely crumbled when removed. I suspect this high attrition rate may be due to high temperatures in an enclosed space.
2nd VFO underside after refurbishment
2nd VFO top side after refurbishment
The photograph on the right shows the extra 10nF capacitor that is added to isolate the 250V HT from one of the coax outputs at the rear of the receiver. Without this modification it is possible to expose the user to a nasty belt. Full details of this modification and the replacing of R76 with an RFC can be found in EMER E727.
The photograph on the left shows the new bolt-on dial brakes. The fitting of which is detailed in EMER E727. In this instance, both older stick on pads had perished beyond usefulness. Also, the adjustment was so far out that only the MHz dial brake was making contact. The way to set these brakes is to loosen the two grub-screws on the rear pad and press it against the KHz fly-wheel with the brake OFF, Now apply the brake and temporarily tighten one of the grub-screws.
Mark the shaft and bush before loosening the grub-screw. Now release the brake and move the KHz brake arm very slightly counter-clockwise and re-tighten both grub-screws. This ensures that with the brake applied, the pad is compressed against the fly-wheel. There should not be any need to adjust the MHz pad since it is held against the MHz dial by way of a spring as seen in the photograph.
