Wireless Set No. 52 Canadian - Project

[Harry Moon]

Originally Posted by Bruce MacMillan

Harry, check out the Burnaby Amateur Radio Club. There are a few members there that also belong to the SPARC radio museum so they speak tube language. They may be able to point you in the right direction. Sadly the three people at SPARC that worked on military sets (me included) have moved away.

thanks Bruce

[David Dunlop]

First off, I am stunned at how pristine the interior chassis of this Supply Unit is to look at. Photos will eventually follow.

I took some time to explore the disappearing 2.0 Volts DC from the Low Tension side and discovered absolutely nothing is wrong with this part of the Supply. Whatever I feed into it, shows up perfectly on the +12 Volt Receiver Pin on the rear Connector of the Supply. So!

I have a Main Set Receiver that reports spot on accurate voltages on its meter when fed by the Remote Receiver Supply. When in the Carriers No. 4 and fed with the Supply Unit, the 2 Volts disappears. When the Supply Unit is out of the Carriers No. 4 is shows perfect LT operation. In the Carriers No. 4, 2 Volts disappears. That points to a fault, probably a poor solder joint, in the PLUG ASSEMBLIES, Multi running along the back of the Carriers No. 4. Not exactly the nicest part to have to work on, but at least I know the Supply Unit is looking really good in that circuit.

David

[David Dunlop]

In this post, I want to simply highlight the physical damage this Supply Unit has received. None of it looks even remotely Military Service related and I suspect at least three quarters of it all took place at the same time.

The three common bits of damage are in the first three photos.

Photo 1 is a view of the top edge of the front main panel where somebody took a hammer to it, or a piece of round bar. At first glance, it looked like the work of a small diameter grinding tool, but when you look closer, you can see the effects of an impact force coming downwards and towards the front of the panel. The paint has chipped away from the front face and this impact edge is smooth. The inside edge of the panel, on the other hand has mushroomed in towards the chassis frame. Also, the force of the impact on the left most dent caught the eye screw and crimped it enough the aerial connector cable between the Receiver and Sender can no longer fir through it. Easy enough to restore the eye screw and I think it may be possible to run a simple weld bead along the edge of the panel metal at each dent and dress them down to remove any sign of the dents before I get around to refinishing the front panel. It is interesting to note just how clean the Blower Motor assembly and its related capacitor are compared to the one in the Sender last year. Even better, the dirt on this blower wipes away with a finger.

Photo 2 is the Modification Card Holder mounted to the upper chassis support plate. Note the two dents in it roughly at the midline. They look like the ball end of a hammer was active here. This holder can be removed, straightened and cleaned easily enough, and if needs be a quick zinc plating will restore if nicely.

Photo 3 is the ball end of the hammer at work on the right end of the upper rear chassis frame. Not much I can do about this damage. Most if it is right on the angle edge of the frame piece and pretty much impossible to get at. But the dirt should clean up from around it OK.

It is these three bits of damage I suspect all took place around the same time when this Supply Unit had been pulled out of the Carriers No. 4 for some reason.

Photo 4 is the last bit of physical damage that I have found that makes no sense to have happened in Military Service. It looks very much like somebody wanted to have a look inside this 5-Pin Connector. The body of the connector shows signs of being held in either a vise, or vise grips, while another set of pliers went to work attempting to pull the central core out of the connector. Clearly they did not succeed, but the connector is distorted beyond use now. Fortunately I have an NOS spare on hand I can swap out once the front panel comes off for restoration.

There are a few other physical oddities that have shown up, but I am pretty certain they are part of the Military Service History of this Supply Unit and I will cover them later.

David

[David Dunlop]

A bit of an ‘Errands Day’ today, but I have managed to remove the Vibrator Supply from the Supply Unit. A simple enough task as one just removes the two drop leads from the front clips, unlocks the two Cowl Fasteners and pulls on the handle.

In Photo 1, you can see the two side flanges of the inner sheet metal case for the chassis of the Vibrator Supply and at the back bottom, the small square cut-out in the case that allows the three banana plugs to connect with their sockets. These are the +12 Volt and Ground Input Feeds and the +150 Volts and Common Ground outputs.

In Photo 2 you have a side view of the Vibrator Supply Cover stuck in position where it blocks access to the right side upper and lower Rotary Transformer Mounting Hardware quite effectively. Note, however, the delightfully clean look of the chassis. Apart from the heavier staining/dirt at the very front and top surface of the chassis , the rest is just upper surface dust. I am being spoiled!


David

[David Dunlop]

Not actually knowing what the problem was, I probably erred excessively on the side of caution when it came to attempting to remove the Cases, Metal C1 from its tray in the Supply Unit. After carefully looking in all the usual places for signs of rust, varnish, or even soldering/welding, and finding none, I decided the best approach was to use a small block of wood against the central outer edges of the case at the exposed back of it, and start tapping with a rubber mallet.

The fist couple of taps got the Case to back out about an eighth of an inch, which was a very good sign. About 5 minutes of alternated taps from side to side eventually got the Case out until just over an inch was still in the Supply Unit. At that point, a quick, straight out tug, with hands on each side of the Case, brought it out, for what I now realize, was the first time since June 1966.

In the first photo it is now sitting free beside the Supply Unit.

The second photo shows the Case sitting on its right side with the front facing to the right of the image. You can see the slight oxidation along the lower edge of the side where it sat in its tray. Note the interesting patch mark in the upper left rear corner of the side. I did not realize the significance of this right away.

The last photo is the top of the Case, again with the front facing to the right of the image. At the back of the case, about an inch or so in, you can just see traces of a line running perpendicular to the longitudinal axis of the Case. This is a good thing. The long line running the length of the Case, and the other shorter ones, are not.

The Canadian Marconi Part Number stamped onto the top of the Case was also a surprise. This is the first time I have ever seen a CMC Part Number using a ‘Forward Slash’ between the two parts of the number. Every other CMC Part Number I have seen to date has used a ‘Dash’.


David

[David Dunlop]

The first thing I noticed once I had successfully removed the Cases, Metal C1 from the Supply Unit was a small piece of manila sheet sitting near the back of the tray the Cases rests in, with one side of the manila heavily varnished. The piece of manila is 1-3/4 inch x 2.0 inches. As I was lifting it out of the tray, I spotted a small machine screw sitting in the right, rearmost depression of four stamped into the floor of the tray, in the back half of it. These four depressions form legs, which are spot-welded to the chassis frame of the Supply Unit to secure the tray in place. This screw is a 6-32 x 3/8-inch machine screw. As I was removing it, I spotted straight away that it had come from the right rear end of the tray assembly. The back part of this tray is stamped from a thicker piece of sheet steel and forms the mounting bracket for the brown phenolic plate the holds the three Banana Sockets that accept the corresponding three Banana Plug Power Connectors from the Receiver Vibrator Supply. The sockets are designed as a loose fit on the phenolic board to allow them to easily line up with the plugs when the Vibrator Supply is slid into the Supply Unit and locked in place.

There was no sign of the hex nut or internal tooth lock washer for the loose 6-32 machine screw, and I do not recall ever finding them in the Carriers No. 4. The washer fits under the head of the screw at the front of the tray assembly, but the only way I can see to get the hex nut installed is to slide it in place in a thin was wrench, like those used for working in ignition timing points. Access is completely hidden by the right rear Supply Unit chassis angle. That ought to be fun.

Turned out the manila sheet came from the upper left side corner of the Cases, Metal C1 as seen in the photo I posted previously. It was varnished in place there to prevent any possible shorting contact between the Cases and the Negative Low Tension Brush Holder assembly of High Power Rotary Transformer MG-2A, when the Cases, Metal is in place.

Photo 1 shows the manila sheet and machine screw as found.

Photo 2 is a shot looking directly down the tray assembly from the front of the Supply Unit. It is a pretty good view of the rear phenolic panel holding the three Banana Plug Sockets and you can see the hole on the rear right end where the machine screw fell out. Also, on the tray floor at the very back you can just see the shadow in the dust where the manila sheet was resting, and the four, stamped depressions/feet for the tray can be made out just forward from that shadow.

The final Photo shows the Negative Low Tension Brush Holder of the HP Rotary Transformer, which would be at risk of shorting without the manila sheet on the left side of the Cases, Metal C1. And also in this photo is a good view of the modification to the resister terminal I mentioned earlier, where it had to be wrapped in electrical tape to better insulate it.

David

[David Dunlop]

This simple little part is similar in purpose, though slightly larger than the plates spot-welded into the upper rear sections of the Carriers No. 4 and the Cases, Remote Receiver. They all ensure adequate ground is maintained with the component chassis mounted inside each compartment.

There is probably the additional benefit for this particular Plates in the Supply Unit as it would also ensure the normally loose fitting Cases, Metal C1 that protects and shields the Receiver Vibrator Supply stays quiet and in place.

Space is extremely limited inside the Supply Unit, so as much access as possible needs to be available for servicing. Directly above where this Plates needs to be mounted on the mid-level shelf sits S-11A, the Dynamotor Input On/Off Switch relay. Canadian Marconi used the front two mounting screws for S-11A to mount the Plates. Metal Spring on the underside of the shelf. This means the open front end of the Plates now covers the rear two sets of S-11A mounting hardware, but everything is still accessible for servicing. That would not have been the case if the Plates had been spot welded in place.

In the photo, you will see a small BA screw sitting roughly between the two Plates mounting pan head screws, and to the left. I will refer back to this screw later.


David