Wireless Set No. 52 Canadian - Project

[David Dunlop]

As I noted back in Post #859, it took a little while to ‘connect the dots’ between the strange set of nine numbered symbols I had first noticed on the Sender Circuit Diagram on Page 203 of the 52-Set Operators Manual, and the actual hardware mounted in the Sender chassis. It was this particular panel, hiding in plain sight, that I finally saw for the first time and allowed me to understand the symbols. The attached photo clearly shows how obvious this panel actually is, if ones eyes are truly open.

I still do not know why these four terminals had to be numbered in reverse order, but they were. This photo also shows the stamped numbers in the phenolic panel very well (common to all three such panels) as well as how the ring terminals and sleeves are set up on the wires connected to the terminals. This feature is also common to all three panels.

Terminal 6 is set up between S13A and C8D, the Grid Coupling Capacitor for V7A (813), L34B, the V7A Grid RF Choke, C26G, the V7A Grid RF Bypass Capacitor and S16A, the Mode of Operation Switch. Also tied into it is R8A, the Parasitic Suppressor feeding to Pin 4 (Grid No. 1) on V7A. This all caught my attention since the Pin 4 circuits are giving me the bulk of the bad readings for V7A at the moment.

Terminal 7 is between S13A and C27F on Pin 3 of V5C, the Plate Coupling Capacitor, L43A, the V5C Grid 7 – 16 MC Tank Coil, and C17A, the variable V5C Plate Tuning Capacitor.

Terminal 8 is between S13A and L34C, the V5C Grid RF Choke, C27F on Pin 3 of V5C, the Plate Coupling Capacitor, and R39C, the V5C Screen Voltage Dropping Resister, and R7E, the V5C Screen Parasitic Suppressor on Pin 4 of V5C.

Terminal 9 is the last of this series of screw terminals. It is situated between S13A and R57A and R57B, a series set of 600,000 Ohm HT Metering Resisters, and C26H, the V7A Screen RF Bypass Capacitor connected to Pin 3 (Grid No. 2) on V7A. This circuit is now also of interest since the meter reading for the Sender HT Circuit was only giving me 110 Volts DC (+/-) when the Supply Unit was running, and the actual readings should be either 300, or 600 Volts DC, dependant on whether one, or both of the Supply Unit Dynamotors are running.
So it looks like the time it took to trace out what these nine terminals are doing in the Sender was a worthwhile effort as it gave me a better focus on where two of the major problems with the Sender circuits might be located.

David

[David Dunlop]

This last photo of the underside of the Sender chassis actually covers where all three of the just discussed screw terminal panels are located.

As you can see, the 4-Terminal panel jumps right out at you when you know what you are looking for, but the 2-Terminal panel in the section just below it is a lot harder to find and recognize. And in between these two in terms of ease of recognition, is the 3-Terminal panel tucked down in the lower right corner, behind the L33A coil.

Why Canadian Marconi Company used these three panels where they did, I still do not understand. I like the idea Chris put forward that it may have provided advantages on various parts of the assembly line for subcomponent assembly and testing, before these items were delivered to the main assembly line for actual installation into the Sender chassis units. There does not seem to be much advantage to them for subsequent maintenance or servicing at the moment. As Jacques Fortin said when I brought them to his attention, if no further information turns up, they shall be added to the CMC List of Secrets for the 52-Set.


David

[David Dunlop]

Before I plod along any further, I just want to correct an error on my part in terminology.

Over the last few posts on the three screw terminal panels, I had been referring to the fittings attached to these panels as ‘Ring Terminals’. I became suspect of that identification this morning and decided to confirm what they are more closely.

As per the attached photo, these fittings are actually ‘Fork Connectors’, but of a type I cannot recall ever seeing a modern equivalent of in any electronic supply shops today. Note that the inner throat of the fork is designed to also serve as an integral lock washer.


David

[David Dunlop]

A short and good week so far.

I received a phone call from Anything Custom, a local machine shop, on Tuesday advising two small items I had asked them to fabricate for this project, were ready for pickup.

This particular item used to be a 3.5-inch long piece of ½-inch copper water pipe. I needed it to be pressed flat to form a small copper buss bar that will serve as the key part to a Ground Terminal for my wireless equipment.


David

[David Dunlop]

Going all the way back to the 1970’s, I have never bothered hooking my two Wireless Sets No. 19 to a Ground Terminal when operating them, in spite of recommendations to do so in the various 19-Set manuals. My excuse was always that it was too much work to run a proper Ground Line into the part of the basement the wireless equipment was set up in.

That changed a couple of years back when the bathroom next door was renovated. I actually took the time to take advantage of opened walls and ceilings to run a continuous transmission cable in from the aerial in the back yard to the wireless equipment, and also a proper ground line. As far as I got at the time with the Ground Line was a foot long lead of copper wire poking through the wall under my wireless bench and a running idea of how I wanted two related terminals set up.

With the 52-Set being the powerhouse it is, I finally caved and decided to get this Ground Terminal completed and ensure all future operation of either the 19-Sets, or the 52-Set will be done with the equipment properly grounded.

So, in addition to the piece of water pipe that has now been flattened, the attached brass hardware and 4-inch square, plastic electrical box have been added to the parts to complete this Ground Terminals sub-project.


David

[David Dunlop]

This was the second small item I had fabricated at Anything Custom.

It is a replica of the bracket removed from the right rear wall of the tool box and it would have supported the right hand end of the wooden Hydrometer Storage Case.

Once I have drilled the mounting hole and given the bracket an aged patina I will install it.

I you want to recap the story of this tool box, I starts with its discovery and arrival back in May, 2018 (Posts #65 - 69), refabrication of the missing wooden partition (Posts #321 - 323), in 2020 and a test fit of the Irons, Soldering in Post #403.


David

[David Dunlop]

This morning was spent marking out and drilling the three holes in the copper bar, for my Ground Terminal Project. The hardware is all ¼-inch brass, but I went to 17/64-inch for the hole size, just to make assembly a little easier.

Once the holes were in the copper bar, I used the bar as a template for getting the two terminal post holes properly centered on the cover of the electrical box.


David