Wireless Set No. 52 Canadian - Project

[David Dunlop]

Well it was an interesting weekend, lots of pluses for the most part, and fortunately, only one rather spectacular negative.

I was able to narrow down the possibilities for the poor performance of my Main Set Receiver to the 1st and 2nd IF Amp sections and Valve V1D in particular. The valve itself was in good working order, but one of the other components that should have been working well with it, was not.

So I took the receiver, along with my Remote Supply bits over to a friends on Sunday morning to take advantage of his far greater electronic expertise, and shop full of test equipment.

As I had suspected, the receiver was working very well both ahead of and behind the two IF Amp stages and we eventually worked our way towards the eight small trimmer capacitors set up in two banks of four in the pair of IF Coil Assemblies. This receiver, as in my Remote Receiver, has the upgraded Trimmer Capacitors that were issued 24 April 1959 for replacement of the originals.

These new capacitors were identified as:

CAPACITORS, Variable, air dielectric 7.5 to 99.0 uuf CT1B100 and came with a NATO Stock Number 5910-00-126-1583

I suspect they are a Hammarlund product and the ‘CT1B100’ might be their part number reference.

The original capacitors issued with the 52-Set were also very likely made by Hammarlund. They are described as:

CAPACITORS, Semi Fixed, 5 – 100 uuf, 10% ZA/CAN 4478

The first we attempted aligning, C7D, would not budge at all and we could see it had a coat of varnish on it, none of the other seven had showing. That should have been our first clue. Five of the remaining seven were almost spot on and needed little or no adjustment. The two others were off by quite a bit and things were sounding very promising as they were brought into alignment. That just left C7D, so we headed back to it.

With the second careful attempt at turning the inner adjusting shaft, it suddenly unfroze and started turning and things were sounding REALLY good! It was just coming up to its optimum alignment point when we heard a loud metallic ‘ping’ from inside the capacitor, the adjusting shaft parted company with the adjustment tool and bottomed out deep inside the outer support tube, and the small hex head collar that locks the shaft in position bounced onto the bench. Not good!

An inspection of the hex collar showed it was cracked right through one face and the crack had a lot of dirt in it, all the way through. Taking into consideration the air gaps between the fixed stator and adjustable rotator plates inside this capacitor are on the order of 1/64-inch wide, and the adjustable rotator shaft suddenly moved inward under its tension spring load a good 5/16-inch. I am pretty much assured this capacitor is now toast.

The two photos show the shaft settled deep inside the capacitor now and the crack through the hex collar.

I do have 8 of the original capacitors available from the Spare Parts Receiver and a quick look indicates they are probably all in good working order, but it would be nice to find an original upgrade version for the replacement project.

OF course Hammarlund went out of business in the late 1970’s, so another challenge ahead with the Main Set Receiver. Sigh!


David

[David Dunlop]

A little bit of an update on the C7D Trimmer Capacitor Saga.

I have been able to successfully retrieve the C7D Trimmer Cap from the spare IF Coil Assembly salvaged from my Spare Parts Receiver. Only two soldered connections to deal with, both involving a very tight wrap of 20 gauge solid copper lead, and I have never seen so much solder on connections like these two had accumulated. I used up nearly 3 inches of de-soldering wick on them before deciding there was no way I was going to be able to clean the terminals enough to unwrap the leads. So I had to finally resort to my least used and least favourite tool in the shop: cutters.

But the replacement C7D Trimmer Cap is now ready to install in the Main Set Receiver, along with its insulating shield for the long Rotator Plate Connector.


David

[David Dunlop]

The Project is in a temporary holding pattern for a while.

I realized once I had the spare C7D Trimmer Capacitor ready for installation, I did not have any 20 gauge tinned, solid copper hook-up wire available in black insulation to make up the two connections between the C7D and its related coil. I have now ordered a 25-foot spool from the local Electronics Shop and have to wait for it to come in for pickup.

In the meantime, I have continued to review the steps needed to do the swap of the Trimmer Capacitor in the Main Set Receiver. It has been an interesting process with several modifications taking place in my head over the last few weeks.

Step 1 is I have to unsolder the Grid Cap Clip for Valve V1D inside the front section of the receiver and solder on a temporary extension of about 6 inches. This lead only has 2-3/4 inches of free place with the Grid Cap Clip removed before the lead will disappear inside the coil shield. The shield cannot be removed because there is not enough clearance to do so with the front panel attached to the receiver. The extension will allow me to retrieve the Grid Cap lead and re-solder the clip to it when the swap of C7D is completed.

Step 2: On the back side of the receiver, as shown in the attached photo, The C7D Trimmer Cap is the top most component on the left hand diagonal IF Coil Assembly. From approximately the mid-point of the assembly to the top, there are three individual wires that will have to be unsoldered: a long one going up above the coil assembly and a medium and short length set at roughly the mid-point. With them free, the large wiring loom coming off the bottom of the coil assembly, leading to the SHARP/FLAT Switch is the only thing holding the coil assembly in place once its mounting screws are removed.

The two IF Coils are 3-3/4 inches long wrapped on brown phenolic tubes. Strips of cotton cloth tape hold them in place on the tubes and then the entire coils are dipped in bees wax to protect the very fine wiring of the coils.

The punched holes in the rear chassis panel have some pretty keen edges. It would not take much contact with them for the wax and wire coils to be trashed, so the entire assembly has to come straight back out of the holes roughly 4 inches to be safe.

The loom feeding to the SHARP/FLAT Switch has been sitting in that position for nearly 70 years and I have no way of telling for certain if it is natural or synthetic rubber. The wires have also been treated with fungicide varnish so overall are pretty stiff. There is only about 2-1/2 inches of play in that loom before it reaches its limit and the coil assembly will start to get pulled to that side. Not good.

My first thought was I would have to unsolder all the connections at the SHARP/FLAT Switch, which was not a popular thought in my head. I then remembered the disassembly process for the Spare Parts Receiver.

The only electrical connections at the back of this switch are to the two IF Coil Assemblies. The switch has a big long shaft that runs to the lower front of the receiver and the hole in the front of the chassis simply supports the shaft. The switch is actually held in place on the chassis by a mounting plate at the back end with two screws securing it. For reference, there is a photo of this switch in Post #633.

Step 3, therefore, will be to remove the knob from the front of the SHARP/FLAT Switch shaft and then remove its two mounting screws. The entire switch can then be moved back to clear the front panel of the receiver and then swung down and to the right in the attached photo to rest directly under the two IF Coil assemblies. It can then be careful moved straight back with the IF Coil assembly containing the C7D Trimmer Cap until the two coils clear the rear chassis panel. With lots of TLC…it should work…I hope.


David

[Bruce Parker (RIP)]

Originally Posted by David Dunlop

I have now ordered a 25-foot spool from the local Electronics Shop and have to wait for it to come in for pickup.

25 feet should cover this and many subsequent 52 set rebuilds. Are you not telling us something?????

Anyway great restoration and it's always a pleasure to see how you come up with modern solutions to 75 year old problems. I bet you are the only one of 7.9 billion people doing what you're doing.

And besides all of that, 52 sets are some perdy.....

[David Dunlop]

Gosh, Bruce.

As you probably know, the wartime era Military District 10 was headquartered here in Winnipeg at the old Ft. Osborne Barracks. The old ‘District’ structure was abandoned after the war and the ‘Command’ structure adopted and by the late 1950’s, Kapyong Barracks had been built just south of the Ft Osborne site, which was abandoned to the Provincial Government for use by a few Departments.

In the 1980’s the site, which had remained intact from its wartime days, was handed over to a private group and it became a new university campus.

I would LOVE to say I found 10 complete 52-Sets still crated in an old forgotten storage room, but no such luck! Not even one badly used one! But if it ever comes true, you will be one of the first to know!

This Project is definitely a challenge, but I really enjoy research and learning new things and that certainly helps balance out the challenges.

The other nice thing is the amazing assistance and support available from MLU members. As much as this site might be considered vehicle oriented, military vehicles all too frequently were equipped with complex, unrelated equipment like wireless kit, that draws expertise in from other areas. Sooner or later, all these little bits come together and we all grow that much wiser for it. Our sanity might be questioned a bit, but I think we do get wiser.

David

[David Dunlop]

Although I am physically inactive with the 52-Set Project at the moment, my Mind plays by a different set of rules. In this instance, it is firmly entrenched in the next step beyond getting the Main Set Receiver back up and working. It is merrily churning up all sorts of things relative to the Supply Unit.

One of the things on my Mind is the above noted parts, the conical rubber connectors between the various headsets and drop cords found on many wartime Commonwealth Wireless Sets. On the 52-Set, there are two 5-Point Sockets, No. 5 mounted amidships on the Supply Unit, of which one socket looks like it had a blow torch applied to the end of it, it is so badly deformed. So it will end up getting replaced with an NOS spare I have on hand.

Currently, on the “wireless-set-no19 Group” website in England, there is a very interesting topic running about the chronic failure of all sorts of electrical wiring in the Clansman and Larkspur wireless sets. The rubber insulations crumble rather like the wartime synthetic rubber tyres used to on CMP vehicles.

That thread brought me back to these wireless connectors. I have a headset connected to my Wireless Set No. 19 Mk III, which I still fire up from time to time and the plug and socket were last disconnected from one another some 20 years ago. It was a relatively easy thing to do. Gently flex the joint between the two pieces until the metal retaining ring popped out of its groove and then pull the two pieces apart. I tried doing that a couple of years back when I started the 52-Set Project and the first thing I noticed was the two rubber cones felt VERY hard and there was definitely no desire for the area around the joint to flex at all. So I stopped trying.

While looking for Headsets No. 10 for the 52-Set, I found a minty set on which the central rubber plug in the connector had been popped free. Why this was done I do not know, but it looked like a screwdriver had been dug about in the seam between the two parts to accomplish the task. Electrically this headset is perfect, but for the life of me I cannot reinsert the circular plug back into position. The rubber is just too hard.

What my Mind is playing with now is the notion I may very well get the complete 52-Set restored and running perfectly but not be able to connect a headset to it because all these conical rubber 5-Point Plugs and Sockets have hardened up too much over time.

So my questions are if anybody else has noticed these Plugs and Sockets have hardened up, is anyone still able to easily connect and disconnect these pieces on their wireless sets and is there a way to refurbish these pieces…just in case?



David

[Bruce Parker (RIP)]

Dave, they all harden over time and better storage only slows the process. For my operating 19 sets I leave the headsets plugged in rather than risk breaking them. I've also noted that sunlight and warmth softens the snatch plugs as well as No.8 and No.9 aerial bases (this I discovered by accident when displaying vehicles with radios at various shows). A long term make work solution would be to cast new ones. The sculpture supply store I go to has dozens of plastic/resin mold materials one of which I'm sure would duplicate the right WW2 rubber consistency.

Originally Posted by David Dunlop

Although I am physically inactive with the 52-Set Project at the moment, my Mind plays by a different set of rules. In this instance, it is firmly entrenched in the next step beyond getting the Main Set Receiver back up and working. It is merrily churning up all sorts of things relative to the Supply Unit.

One of the things on my Mind is the above noted parts, the conical rubber connectors between the various headsets and drop cords found on many wartime Commonwealth Wireless Sets. On the 52-Set, there are two 5-Point Sockets, No. 5 mounted amidships on the Supply Unit, of which one socket looks like it had a blow torch applied to the end of it, it is so badly deformed. So it will end up getting replaced with an NOS spare I have on hand.

Currently, on the “wireless-set-no19 Group” website in England, there is a very interesting topic running about the chronic failure of all sorts of electrical wiring in the Clansman and Larkspur wireless sets. The rubber insulations crumble rather like the wartime synthetic rubber tyres used to on CMP vehicles.

That thread brought me back to these wireless connectors. I have a headset connected to my Wireless Set No. 19 Mk III, which I still fire up from time to time and the plug and socket were last disconnected from one another some 20 years ago. It was a relatively easy thing to do. Gently flex the joint between the two pieces until the metal retaining ring popped out of its groove and then pull the two pieces apart. I tried doing that a couple of years back when I started the 52-Set Project and the first thing I noticed was the two rubber cones felt VERY hard and there was definitely no desire for the area around the joint to flex at all. So I stopped trying.

While looking for Headsets No. 10 for the 52-Set, I found a minty set on which the central rubber plug in the connector had been popped free. Why this was done I do not know, but it looked like a screwdriver had been dug about in the seam between the two parts to accomplish the task. Electrically this headset is perfect, but for the life of me I cannot reinsert the circular plug back into position. The rubber is just too hard.

What my Mind is playing with now is the notion I may very well get the complete 52-Set restored and running perfectly but not be able to connect a headset to it because all these conical rubber 5-Point Plugs and Sockets have hardened up too much over time.

So my questions are if anybody else has noticed these Plugs and Sockets have hardened up, is anyone still able to easily connect and disconnect these pieces on their wireless sets and is there a way to refurbish these pieces…just in case?



David