Photo's for the THE RESTORATION OF VALVED HIGH FREQUENCY COMMUNICATIONS RECEIVERS ebook.
Racal RA17 original prototype. The left and right are NOT two separate castings. Difficult problems of spurii led to the original single casting being bandsawed into two completely separate halves. Look carefully and you will see the sawcut! This broke the path of the earth current, enabling correct performance to be achieved.
AWA CR-6B chassis underside showing the proper fitted cover beneath the RF unit to stop draughts and promote frequency stability. The mighty bandchange roller chain is rather as seen in the RCA AR-8516L - but the AWA implementation works better. The selectivity wafer switch at the top of this photo forms part of the IF block filter module. Notice how easy this set is to work on - very intelligent design.
AWA CR-6B close-up of the selectivity switch, carried on a metal bracket which also accommodates the five 100kHz IF coils. No nasty micas to drift away from the correct values! Notice how the main radio chassis is fitted with Mullard tubular polyester capacitors. These are about the only type still considered reliable some fifty years after they were made.
KW2000E vertical FR4 PCB was termed the “KW Vox Box”. It may perhaps have been standard fit instead of an option as on earlier models. The oversize washer on the PCB corner was fitted by the writer to protect transformer IFT5 when the chassis is being handled on the bench. The large B9A valve fitted with the spring retainer is the ECL82 for audio output.
KW2000E rear panel, showing the small Painton multi-way connector which carries raw mains, +1000V HT off load, and transistor supply voltages from the external PSU box. The metal shell of the mating connector is not even grounded. This is extremely dangerous equipment design. Notice the absence of a “Danger High Voltage” warning label. There should certainly be one!
KW2000E showing plastic boxes added by the writer to improve frequency stability and reduce dust ingress. Notice the yellow Kapton tape covering a hole on the top of the VFO module. This aperture is directly below the finger-hole in the cabinet top cover. A delicate Philips beehive trimmer lies directly underneath. The tape stops debris falling into the VFO, and also captivates the bulb wiring.
RCA AR-88D chassis underside, showing excellent screening arrangements. All rotary switches have ceramic wafers like those shown here. The multisection smoothing block is being rebuilt using 3 pairs of 10µF/450V/105°C high reliability electrolytics in series, each capacitor strapped by a 220kΩ TR6 metal oxide voltage balancing resistor. This gives 5µF/900V/105°C per section instead of 4µF originally, with a total effective bleed resistance of 147kΩ.