Wireless Set No. 52 Canadian - Project

[David Dunlop]

Well the first discovery about this Coil assembly with it finally out on the bench for a closer look, was a very positive one.

What looked like a very odd oxidation on the brass gear set for the coil tuning turned out to be a very nice distribution of a medium weight grease which was in excellent condition. Probably applied back in the 1966 Workshop overhaul for the set. The grease shall stay. It has earned its place.


David

[David Dunlop]

The design of the Coil, Aerial Tuning No. 2 A is slowly revealing itself, in spite of not much being said about it in the documentation for the 52-Set. The only technical references it gets are that it is not to be used at all above 10 Mcs and the Sender is to be connected directly to the aerial in use, and, that it is fully interchangeable with the Coil, Aerial Tuning No. 2, issued with the Wireless Set No. 9 Mk I Cdn.

One thing that has now surprised me, because I have missed it for several years now, is that the front panel for the Coil is cut from 1/8-inch Aluminum plate whereas all the other components in the 52-Set have front panels cut from 1/16-inch sheet steel. I am glad I now found this out as I have no primer for working with aluminum when it comes time to repaint the Coil front panel. That product is now on my ‘To Be Purchased’ list.


David

[David Dunlop]

While inspecting the Coil I am using for the 52-Set, I found ‘3978’ stamped in blue ink on the bottom side of the phenolic resin base of the coil chassis itself. I then found the same number stamped on the outer surfaces of the resin left and right side panels. See the first three photos. I am thinking this might be a Production Control Number used by Canadian Marconi Company during the manufacture of these coils, in a similar manner to the hand written four digit numbers found on the inside chassis surfaces of the other set components. The only other stamped marking I have found so far is the part number for the coil itself, CMC 119-521, which was stamped along the left side edge of the coil drum as shown in the last photo.

Now I have to see what I can find on the parts coil assembly.


David

[David Dunlop]

My parts coil revealed the number ‘8798’ stamped on the same parts as the four digit number that was found on the Coil assembly for the 52-Set, as per the first three photos.

The main difference was the Part Number for the Coil itself was not along the left edge of the drum, but now located on the left side plate of the drum. See last photo.

So if these numbers are indeed Production Control Numbers, then this Coil assembly came down the line a lot later than the first one. Is the new location for the coil Part Number as production change for some reason, or just a fluke?



David

[David Dunlop]

For such a small, and electronically simple component of the 52-Set, this coil assembly holds an amazing number of mysteries for me and they just keep popping up!

In fairness to the Engineers and Designers at Canadian Marconi Company 80 years ago, a fair bit of these mysteries are probably directly related to my limited practical and theoretical electronic knowledge related to this calibre of wartime wireless equipment.

The first, and still current mystery, revolves around the existence of the small cylinders found mounted just below the tuning gear drive assemblies on the right side plate of the coil chassis as per the first photo. They are not physically connected to any circuit in the entire coil case, just the 1/4-inch resin side plate. My first thought was they contained a coil intended to balance out the presence of the large mass of metal present with the tuning gear drive next to it.

Last night, however, I discovered these cylinders are not hollow. The ends of the two I have available to study finally revealed they are a tight roll of resin impregnated fabric. It is still possible that a very fine weave of non-ferrous mesh, or foil, is wrapped up within the coils of fabric, and these cylinders are serving some form of electronic purpose.

A new ‘longshot’ idea is these cylinders are nothing more than a spacer, or guard, to protect the tuning gear drive from getting knocked out of alignment when the coil assembly is removed from its wooden case. I say ‘longshot’ because a 2-inch piece of 3/4-inch wooden dowel would have been a far cheaper and simpler solution for this type of problem.

Adding to this mystery is the complete lack of reference anywhere in the 52-Set documentation to these resin cylinders.



David

[Mike K]

Originally Posted by David Dunlop

A new ‘longshot’ idea is these cylinders are nothing more than a spacer, or guard, to protect the tuning gear drive from getting knocked out of alignment when the coil assembly is removed from its wooden case. I say ‘longshot’ because a 2-inch piece of 3/4-inch wooden dowel would have been a far cheaper and simpler solution for this type of problem.


David

Yes I believe they are just spacers that provide some mechanical stability to the rotary inductor frame and also prevent damage to the inductor unit mount which looks like a phenolic sheet material.

[David Dunlop]

Hello Mike.

The frame work is actually 1/4-inch phenolic plates, assembled at the factory with zinc, or cadmium plated, brass brackets and hardware, another part of the design showing CMCs desire to avoid the presence of ferrous metal in the construction of these Coils, Aerial Tuning No. 2 A, at great length.

They seem to have not wanted any latent magnetism developing within these units at all costs, and I fear I am not yet wise enough to understand why. Insert “Sigh” here.


David