[David Dunlop]

Once I had removed the COVERS, Metal, No. C1 from its retaining brackets on the rear of the Carriers No. 4, things suddenly started to make much more sense in the Instruction Manual for the 52-Set. In particular, Section 6.11 starting on Page 137. This section explains the correct procedure for reinstalling the Receiver, Supply Unit and Sender into the Carriers No. 4, if all three have had to be removed at the same time for any reason.

The only thing that holds the PLUG, Assemblies, Multi to the 52-Set are the five individual Bakelite plugs themselves, once they are pressed into the five corresponding sockets fitted to the back of the three set components. If none of the three components are present, the PLUG, Assemblies, Multi becomes a free-floating object inside the Covers, Metal, No. C1. As a unit, this PLUG, Assemblies is heavy and the vertical wiggle room within the Covers is not enough to prevent the Plug and component sockets from lining up with each other. Same for the lateral movement to either side of the set. With the Cover screwed in place, the two Cover Retaining Brackets either side minimize the side-to-side wiggle of the Plus Assembly to acceptable limits. The exception is the depth of the Covers. See the first photo.

The internal depth of the Covers, Metal, No. C1 is twice that of the Plug Assemblies, Multi. If all three set components have been removed from the Carriers at the same time, as soon as you attempt to replace the first component, it will simply push the Plug, Assemblies, Multi to the back of its Covers, out of reach. You will have no choice at that point, other than to read up on Section 6.11 of the Manual and perform a ‘by the book’ reinstall.

I would also strongly advise you carefully clean the connecting surfaces of both the Bakelite plugs and sockets on the 52-Set. They are a snug fit to start with and it will not take much in the way of fine dirt or dust building up on the surfaces to cause them to bind against each other when being connected or disconnected. They are all black Bakelite and all of mine looked fine at first, but it is amazing how dirty a damp cloth and toothbrush gets when you start cleaning.

It is also a good idea when connecting, or disconnecting these Bakelite connectors, to apply the force you are using perpendicular to the faces of the connectors. In other words, push straight in and pull straight out. If the force you are applying gets too far off the perpendicular, the connecting faces of the plugs and sockets will bind against each other. Bakelite was never a forgiving material at the best of times and these parts are additionally, now 75+ years old. Be nice. The last picture posted here shows the damage that can happen to the Plugs if not treated carefully. Four out of the five in my Carriers No. 4 have this type of damage present.

The nice find was that the paper terminal labels inside the five plugs are minty originals.

The other photo I posted is of the back of the Plug, Assemblies, Multi. Again, a one piece sheet steel stamping, satin nickel plated. The metal gauge seems to be the same as used for the Covers and Carriers.

I have been thinking about the design of the Plug, Assemblies, Multi when it comes to all three components of the wireless set being removed from the Carriers. I have not yet seen any documentation from Canadian Marconi, or the Military end users of the 52-Set flagging this topic as an issue or problem. No revised Covers. No apparent modifications. The logic of the design may be difficult to grasp today, but it would seem to have been a valid design. The same style of connectors system was used by Marconi on wireless sets built for use by the Navy during the war and no concerns appear at that end either.

Two possible justifications for the design come to mind. When mounted on the back of the Carriers No. 4, the Plug Assemblies are open to the inner case of the Carriers. When the fans in the Supply Unit and Sender were operating, warm air would certainly be capable of circulation around the Plug Assemblies so they would stay dry. Secondly, as mentioned earlier, Bakelite is not the most forgiving substance. If the Covers were snugged up against the Plug Assemblies firmly, it is possible the shock of any blow to the surface of the Covers could transfer to the Bakelite connectors and crack them.

That’s all I’ve got on this topic at the moment.

David