[David Dunlop]

A bit of a milestone has now been reached with the work on the 52-Set Sender. I have done all the cleaning I can now with the chassis resting on its back. One small section of the lowermost chassis stills needs to be cleaned – the area surrounding the socket for the 813 valve – but I cannot easily access it until the chassis is returned to its upright position. This, however, cannot be done with all the components normally secured to the front panel, flopping around loose.

Fortunately, I still have the three Flick Drive assemblies to continue dismantling for cleaning and repainting of the Indicator Flags on each. Then it is a case of cleaning and polishing the front of the panel to get it to a point it can be reassembled to the Sender chassis.

An interesting observation at this point should be made though, regarding the Flick Drives used on the Wireless Set No. 52.

I do not think calling these Flick Drives a ‘Standard Feature’ on wartime British wireless equipment is entirely warranted, but they were certainly common to many wireless sets, and they appear to have worked reasonably well up to the time the Wireless Set No. 19 came into service, and the shear numbers of 19-Sets in use, quickly revealed the limitations of these drives. The design was sound, but the products chosen for assembly, quickly proved wanting.

The main problem that came to light by 1943 was that with high usage of pre-set Flick Frequencies, the drives eventually began to fail to return to the chosen frequency reliably. In fact, they would start to drift off the pre-set frequencies so badly, renetting to the required frequency became the only way to get the set back where it was supposed to be. The answer for that with the 19-Sets was the introduction of the Crystal Calibrator unit developed by Canadian Marconi.

In developing what became the Wireless Set No. 52, Canadian Marconi built the Crystal Calibrator designed initially for the 19-Set into the Receiver of the 52-Set. And they went further. In reviewing the concerns raised by the Flick Drives loosing the ability to return to their pre-set frequencies with the 19-Set, two problems were identified.

The BUSHES, Dial, Mounting, No. 2 (ZA 14552) were made of machined, cast zinc. This was found to be too soft and wore out easily with prolonged, repeated use. Canadian Marconi switched to a bronze alloy for these BUSHES on the 52-Set.

The second problem was found to be with the two small BRACKETS, Supporting, No. 1 (ZA 14553) located at the outer, upper corners of the Flick Drives. These had typically been made of small folded steel pieces, screwed to the back plate of the drive. In turn, the front panel of the wireless set was then screwed to these small brackets. It was too easy to strip any of the screws in these assemblies, and the sheet steel flexed too much. This combination would eventually allow the Flick Drive to move as a unit behind the panel when flicking between the two pre-set frequencies. Canadian Marconi solved this by switching to solid bronze alloy BRACKETS, welded in place on the Flick Drives intended for the 52-Set.

A third problem was found to be the steel used in assembling the Flick Drives was too soft. CMC upgraded the specs for the steel they used in their Flick Drive Production.

One extra step CMC undertook was to include the FREQUENCY ADJUSTMENT Control directly above the Tuning Dial on the 52-Set Receiver, just in case a pre-set flick frequency was not spot on when returned to, adjusting that Control would find the correct frequency quickly for the Operator.

The attached photo shows the Bronze alloy BUSHES readily on the three Flick Drives and the triangular plated bronze alloy blocks mounted in the upper corners of the drive assemblies.

This is why the manuals for the 52-Set point out that although the drives and parts thereof are common to both the 52-Set and the 19-Set, 19-Set parts should not be used because they are of inferior quality.

David