Wireless Set No. 52 Canadian - Project

[David Dunlop]

My observations about the number of leads feeding up from the Tuning Capacitor below the COIL ASSEMBLIES proved correct. There were five of them: one coming out the left (inner) side of the Tuning Capacitor and four feeding up through the right hand side of the Tuning Capacitor cover, through small, metal sleeved holes. A bit of a challenge to get at with a soldering iron, but more on that later.

The mounting hardware for the Coil Assemblies is fairly comprehensive, involving 11 sets in total.

On the left side, there are three slot head, countersunk, machine screws. The two upper ones utilize hex nuts and external tooth lock washers on the inside of the receiver chassis wall to secure them. The 3rd screw simply fastens directly into the end of the front support rod assembly of the Coil Assembly. This rod is a three section affair and access to fit an external tooth lock washer on the interior of the left receiver chassis wall is none existent, so to prevent the support rod section at the end from unscrewing when the outer screw is removed, an external toothed lock washer was added to the left end of this outer rod section, between the rod end and the right partition wall of the Coil Assembly.

On the vertical, right rear lip of the Coil Assembly, three holes are provided which drop over three threaded studs fitted down the inner wall of the receiver chassis. With the Coil Assembles in place, three hex nuts and external tooth lock washers hold it in place.

The top, horizontal, left rear lip of the Coil Assemblies fits directly against the rear wall of the receiver chassis and a pair of round head SEMS Fasteners with external tooth lock washers goes there.

The vertical lip down the left rear side of the Coil Assemblies also has provision for three more round head SEMS fasteners and external tooth lock washers.

My approach was to remove all the hardware except the two SEMS fasteners on the top left rear lip first. Then it was easy to support the Coil Assemblies with one hand while removing the last two screws.

The Coil Assemblies is an interesting component when you get it out of the receiver chassis, for a closer inspection. In situ, and looking at it from the front of the receiver, it is clear it is built in three distinct, shielded columns. Each directly under the following Valves, from left to right: V1C Mixer, V1B Conversion Oscillator and V1A the RF Amplifier.

When you start looking at the Coil Assembly more closely, and pay a little more attention to the components identified on the back of it, you realize the three coils in each column, along with their supporting capacitors, are also laid out in a horizontal pattern of three distinct rows. The top row deals with Band 3, 7.0 to 16 MC’s. The middle row deals with Band 2, 3.5 to 8.0 MC’s and the lower row relates to Band 1, 1.7 to 4.0 MC’s.

Combining the Valves and their basic functions, along with the three columns of the Coils Assemblies, the arm waving functions of each column in relation to the Valve(s) it is linked to can be summarized as follows:

The left column is the RF Amplifier Coupling between V1A and V1C, working primarily with Valve V1C, the Mixer.

The middle column is the RF Oscillator working with Valve V1B, the Conversion Oscillator.

The right column is the Aerial Coupling working with V1A, the RF Amplifier. In the last photo posted today, you can see a long wire, with a red and yellow tracer, arcing towards the camera on the left side. This is the output lead that came from the Crystal Calibrator and travelled through the long shielding tube mounted directly above Valves V1C, B and A. The shadow of the tube is visible on the chassis back wall in the photo in the previous Post #635. This lead feeds directly into this right side column of the Coil Assemblies.

I am hoping nothing serious needs repairing on my main set receiver Coil Assemblies. It would be a very challenging component to work on, even by its own on the workbench.


David

[David Dunlop]

The other interesting discovery regarding the Coil Assemblies, RF, was that it was also considered a major sub- assembly of the Receiver by Canadian Marconi Company.

Along the top end of the left side mounting strip of the Coil Assembly another Production/ Control Number was found, as per the attached photo, this number shows as, ‘#6247’.

It is hard to see this number when looking at a fully occupied receiver chassis from the front because the mounting for the Band Switch gearbox blocks a direct view. Then factor in if one was not aware of the existence of this number, one would not be looking for it anyway.

So it seems that as far as the Wireless Set No, 52 Receiver is concerned, the receiver chassis, Crystal Calibrator chassis and the Coil Assemblies, RF chassis all had Control Numbers assigned to them during the production process.


David

[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