[David Dunlop]

At first glance, the two Input Terminals on the Coil, Aerial Tuning No. 2 A appear to be the most basic of parts. Then, when you get your first good closeup look, they suddenly turn into one of the most fascinating assemblies in the entire 52-Set.

These two Input Terminals are located on the lower rear corners of each side of the coil case, directly above the rearmost mounting screws for the two brass Mounting Plates located on the bottom of the coil case. As such, they need to be removed before the two Mounting Plates can come off the case.

On the inside of the coil case, you can see the brown phenolic resin plates securing the two Input Terminal assemblies to the sides of the case. These plates are 3/16-inch thick, 1-7/8 inches long and 3/4-inches wide. they are held in place by an upper and lower set of cadmium plated, RH slotted brass 8-32 x 3/4-inch machine screws, brass Shakeproof washers and brass hex nuts. As a first step, DO NOT attempt to undo this hardware and remove the plate assembly.

In designing the 52-Set, Canadian Marconi Company was concerned the Operators, under less than ideal conditions, could lose critical hardware, like wing nuts and lock knobs. They used two techniques to avoid such losses. One was to drill the tips of screws, mount the wing nut, or knob, and then fit a wire D-Ring through the hole to secure the hardware from loss. The other technique, as they employed here, was to fit the wing nut and then use a small punch and hammer to mushroom the tip of the screw slightly to prevent the wing nut from coming off. So neither the wing nut, or small mounting panel, will through the hole in the side of the coil case. However, if you first remove the hardware from the central terminal stud on the inside, things will become possible. From the outer end of the stud to the phenolic panel, there should be the folllowing plated brass hardware:

1) 10-32 hex nut
2) Shakeproof washer
3) 10-32 hex nut
4) Shakeproof washer
5) 10-32 flat washer.

With all this hardware removed, and with good lighting, you will notice a 1/4-inch ‘square nut’ in the middle of the panel. if you apply pressure with a thumb to the exposed stud in front of this ‘square nut’, while at the same time gently pulling and rocking the terminal on the outside of the case, this stud assembly will pop free of the phenolic panel. You can then undo the hardware securing the panel and remove it from the coil case.

Interestingly, this terminal stud is the only part of these Input Terminals toi get mention in the Parts Lists for the 52-Set. They are machined from 1/4-inch square brass bar stock and are identified as:

STUDS, Brass, Special, ANF 10-32, 1-21/32 inches long, No. C1. ZA/CAN 8048

The finished item was cadmium, or zinc plated, and there is enough information in the description in the Parts Lists that a decent machine shop should be able to replicate them today.

With the two Input Terminals safely removed from the coil case, the only components left to remove are the two Mounting Plates on the bottom of the case.


David