Wireless Set No. 52 Canadian - Project

[David Dunlop]

In the accompanying five photographs, this Capacitors assembly is shown with its ‘COVERS, Metal, Capacitor, No. C1 ZA/CAN 4226’ still fitted. The four wires feeding through the holes on the right side of the Capacitors are a very snug fit, and I thought I would defer to wrestling with them just once, when I need to resolder the wire going to the middle section of the capacitor.

In the front photo, you can see a four-digit number ‘4290’ stamped in black paint. Since these capacitors were of Canadian Marconi Company in house design and manufacture, this could also be another Production/ Control Number.

On the right hand side, an oddity in the design of the COVERS, Metal, shows up. The front most round head, slotted machine screw holding the COVERS in place, sits in an open slot in the COVERS. This would suggest an idea floated at CMC at one time to make the COVERS easy to remove, if needed. However, the remaining three machine screws all pass through simple holes in the cover. No slots there at all.

As noted with the markings stamped at the top of each slot on the right side of the Capacitors Assembly, the three capacitors in this assembly run in sequence from front to back as, C4A, C4B and C4C. The Circuit References for these are: Antenna, Oscillator and Detector.

In the rear view photograph, the CMC Part Number stamp runs across the middle of the assembly. Just above the ‘C.M.C.’ section of this number is a small Inspection Stamp, ‘INS’. A small blue paint dot in the lower left corner notes that this part has been tested as fully serviceable. I am not sure if the sealant used on the large adjustment screw is red paint or sealing wax. It is quite thick and fortunately shows no sign of being broken. The back end of the COVERS in this photo shows a blurred circular CMC Inspection Stamp and this one was redone on the Covers at the rear corner of the top, on the left side.

The fourth photo is the left side of the assembly, which is pretty straightforward.

The last photo shows the bottom of the Capacitors Assembly. The three countersunk screws, with red lacquer over them secure the Capacitors to its heavy gauge U-shaped, base plate. The three round head screws mount the Capacitors to the chassis floor of the receiver.


David

[David Dunlop]

What the Parts Receiver, SN 8349, looks like now.


David

[David Dunlop]

These large shields are the lowermost ones in the photo in Post #639. From left to right, they cover Coils L18A and L16A in the two Coil Assemblies, IF.

With the two sets of hex nuts and external toothed lock washers removed from the shield mounting posts on the backside of the receiver chassis, the shields lift straight back and away.


David

[David Dunlop]

This pair of shields cover the upper pair of coils (from left to right L19A and L17A) in the Coil Assemblies, IF, and differ from their lower counterparts only by the presence of small, metal sleeved holes in the end of them to allow the Grid Cap Clip leads from the coils inside to pass through.

Just enough of a difference to get an ‘A’ added to the end of their ID and a new ZA/CAN Number.

With regards to removing these shields, you have no choice; the Grid Cap Clips must be unsoldered from the ends of the leads. These leads are not long enough to allow the shields to slide up far enough on them to access their solder terminals inside the Coil Assemblies.

Once the Grid Cap Clips are removed and the mounting hardware removed behind the chassis wall, the shields lift off easily.


David

[David Dunlop]

Viewed from the front of the receiver, this is the left hand vertical pair of IF Coils, under Valve V1E, the 2nd IF Amplifier. The upper coil, L19A deals with the input to the 2nd IF Amplifier Valve V1E, and is supported by a pair of Variable Capacitors, C7G and C7H, acting as Trimmers. The Grid Cap Clip lead for V1E feeds out of the shield for L19A.

The lower coil, L18A, deals with the output from the 1st IF Amplifier Valve, V1D and is supported by a pair of Variable Capacitors, C7E and C7F, acting as Trimmers.

In the early production receivers, these trimmer capacitors were quickly identified as prone to failure in humid conditions and were replaced with much better ones and instructions were issued to upgrade the earlier capacitors when found in a set.

For the Grid Cap Clip lead in this Coil Assemblies, a lead wire would have to have been fitted, of sufficient length to exceed what was needed. The lead would have been fed through the shield and soldered in place, once the coil assembly was mounted in the receiver chassis, and a sleeve fitted over the soldered terminal. With the shield then mounted over the coil, the lead could then be trimmed to the required length, a black sleeve slipped over it and the Grid Cap Clip soldered in place. The sleeve was then tied in place. The sleeve on this Clip was a black woven one.

On the back of the chassis wall, six sets of slotted, round head SEMS screws and external toothed lock washers mount the entire coil assembly to the chassis. When the screws are removed, and the two shields up front, the entire assembly can be carefully pulled out of the back of the chassis. Use caution, however, as the black sleeves on the lower soldered terminals of the assembly make the fit quite snug. It does not hurt to compress these two sleeves inward slightly with one hand while extracting the assembly with the other hand, until the sleeves are clear of the rear receiver chassis wall.


David

[David Dunlop]

Virtually all the parts of this Coil Assemblies are identical to the one just discussed in Post #642, but because the electronic parts have different circuit reference numbers for maintenance purposes, this assembly gets a different Identification Name and CMC Part Number.

This assembly is located under Valve V1D when viewed from the front of the receiver chassis.

The upper Coil L17A, with the Grid Cap lead, deals with the input to the 1st IF Amplifier Valve V1D, and the lower Coil deals with the output of the Mixer Valve V1C.

Two Variable Capacitors, C7A and C7B act as trimmers for L16A, and two other Variable Capacitors, C7C and C7D act as trimmers for L17A.


David

[David Dunlop]

This Unit sits on the left side of the rear wall of the receiver chassis, directly under Valve V2A. The Circuit Reference is L20A, in the 2nd IF Amplifier circuit for Valve V1E. It acts as the coupling from V1E to V2A.


David