Wireless Set No. 52 Canadian - Project

[David Dunlop]

I have not yet found any detailed wiring layouts for the Type 10 Headgear in any of the Wireless Set No. 52 documentation, other than the wiring setup for the two 5-Pin Drop Cords mounted on the Main Set Supply Unit. Fortunately, that bit of data matches similar information found in the 19=Set manuals.

So first step was to draw out the 5-Pin wiring in a larger format I could more easily reference while working on the headgear assemblies. The connections for the left and right receivers were readily visible and consistent across all headsets I had available, so I added that to this layout as well.

I knew there would be additional wiring to map out in the microphones once I got them opened up so I sketched out a diagram for the Phenolic Insert Holders & Plates Assembly ahead of time from several spares on hand, and filled it in when I got to opening up the microphone cases. I have added both of those drawings here at the start to get them out of the way.

From the Type 10 Headgear I have available, I suspect production evolved through an early and a late version related to two specific parts of the Headgear: the receivers and a Jumper Wire discovered inside the Microphone Case. Details of those will emerge in due course, but I will start with information next on what turned out to be the earlier version of the headgear.


David

[David Dunlop]

Leading up to this part of the 52-Set Project, I recently checked in with the 19-Set Group in England to get their opinion on the value of cleaning the contacts on the 5-Pin Connector Plugs and Sockets. The feedback was unanimously in favour of clean brass contacts, but to only get them that way with metal polishes, such as Brasso, or my favourite, Autosol. NEVER use files or abrasives as once too much metal is stripped away, the Connector is completely useless.

So my first step at this point was to polish the contacts on both Headgear harnesses I was going to restore: a pair with excellent original looms, 5-Pin Connector Plugs still sporting their RCA Stamps, and the Headset Receivers showing good yellow Philco Stamps and C-Broad Arrow Stamps. The Microphone Cases for both Headgear were NATO Green and there was a lot of dirt on everything and hopefully I had enough spares on hand to see me through any major surprises.

Once the Connector contacts were cleaned, I connected each Headgear in turn to an open Drop Cord on my 19-Set Mk III, warmed it up and checked to see what happened with the Type 10 Headgear.

Beyond the task at hand of restoring the two Type 10 Headgear, this little test revealed a somewhat larger issue that may prove challenging down the road.

The rubber on these Headgear Connectors, and the three Drop Cords on my 19-Set Mk III, have hardened dramatically. I could not get either Headset to fully engage with the Drop Cord. The brass ring just disappeared into its mating connector and that was it. A good quarter inch or so short of fully engaged. Discretion screamed at m not to get picky at that point. The connection established worked and it was still possible to disengage the Connector. I also made a note to myself to NEVER try disconnecting the headset on the 19-Set Mk III. It was last connected back in 1982 and is probably set in place now. I will have to think the hook-up of headgear to the 52-Set very carefully when the time comes.

The first Type 10 Headgear I tested proved interesting. With the 19-Set warmed up and idling, as soon as I tried joining the headset connectors together, Pin-1 on both sides (the Pressel Relay) threw the Set into TRANSMIT Mode and fired up the Dynamotor. Not a good start. So back to the workbench to disassemble the Microphone Case and map out what was going on inside.


David

[David Dunlop]

I will start off this Post with a wee apology for the readers.

In spite of the best-laid plans and intensions, the actual physical work put into restoring the two Type 10 Headgear had no real linear flow two it once underway. I ended up having to frequently hop back and forth between the two headgear and sometimes off in completely different directions in order to sort everything out. It is taking longer than I hoped to pull all that work into a logical, understandable flow to document it all effectively. I have had to take a few more photos of things I missed originally, or take better photos and then sort them all and tie them together with hopefully sensible notes. So please bear with me.

The first two photos here show the actual Microphones Case (ZA/CAN 1557) and Covers (ZA/CAN 1564) along with the Rubber Gasket (ZA/CAN 1565) stuck to the Cover. Loose fitting Gaskets were found in most of the Microphone Assemblies I was working with, but one did show signs of being varnished in place on the Case side. Surprisingly, all of these Gaskets were still very supple. The Cover is secured by four Screws, ANC, Brass, RH, 4-40 x ½-inch and internal toothed lock washers. Once they are removed, you may be able to pull the Cover off the case, but usually I needed to gently inset the blade of a Putty Knife into the seam between the two parts and gently twist them apart. If you are careful, the gasket will simply squeeze out of the way and be just fine.

These photos also show the Buttons, Phenolic, Pressel (ZA/CAN 1556) and Springs, Steel (ZA/CAN 1569) mounted to the outer upper top of the Case by Plates Assembly (ZA/CAN 1568) on the inside. Total movement of this Button is only about1/8-inch, which closes the two Contact Spring sets nicely, assuming they are still perfectly straight and vertical.

About halfway down either inside face of the Case, you can see a set of vertical ridges cast into the aluminum. These engage slots on the outside of the Holders, Phenolic, Insert to keep it, and the Microphone Insert it holds, correctly oriented inside the Case.

The third photo shows the microphone cord Rubber Grommet and Washer factory fitted. The Washer is, in fact, the Anti-Strain for the microphone cord. The large metal crimp securing the loom at the top of the microphone cord has two small rectangular tabs 180 degrees apart, bent up from the cord 90 degrees at the top end of the crimp. The Washer and Grommet slide up against these two tabs. When the rubber grommet is slid down onto its groove on the Case, the Washer slides down the inner face of the Case and is held between the two cast columns for the Cover Mounting Screws. In doing so, it clamps the Grommet is place, making it easy to fit the Cover onto the Grommet when the Cover is reinstalled. If the Grommet has perished and fallen away as many have, the inside half will still be there protecting the cord. The only way to install a new Grommet is to split it open with a sharp razor blade or scalpel and slip the Grommet over the cord. I had to do that one of the Type 10 Headgear I restored. I thought I would explain how it all works here. Oddly, however, I can find no part number or description references at all for either this Grommet or Washer in either the 52-Set or 19-Set documents I have on hand.

The last photo in this Post shows the conditions inside the Microphone Case of what appears to be the earlier version of the Type 10 Headgear, when I first opened it up. A lot of rust dust evident and other signs of high moisture. Interestingly, the Pressel Button still functioned nicely.

Of particular note at this point, are the squares of black rubber coating the upper back portions of the two Contact Spring Assemblies. The other oddity upon opening this Microphone Case up was that the Microphone Insert was well and truly stuck in its Holder Assembly. It should have been a secure fit, but easily pulled free with ones fingers.

As you can see, the wiring is nicely tucked around the perimeter of the Holders for the Microphone Insert. In fact, the lengths of each wire to work with are very consistent with where they have to go for connection. The tracers on four of the five wires match the documentation for the 5-Pin Connector Plug. The one deviation is that a double back tracer has been substituted for the Green Tracer in the manual diagrams. At first glace, it all looks pretty normal, doesn’t it!


David

[David Dunlop]

A nice, hard, flat work surface with a 90-degree front edge can be your best friend when trying to remove the Holders assembly from the Microphone Case. Over the years, fine dust infiltrates the case and finds its way into the two grooves either side of the Holder that slot over the two side ridges in the case. Just enough to make it tricky to get the Holders free and out.

If you turn the Case upside down and hold it at the Spring Contacts end, you can give it a few good, flat whacks on the surface of your work surface and watch the Holders at the slots to see it slowly sliding up on the ridges. Eventually, you can carefully pinch the outer edges of the two Contact Spring assemblies with one hand, and hook a finger of the other hand under the Microphone Cord by the Grommet and gently lever the Holders out of the Microphone Case to work on. With this first Headgear Type 10, I was not so lucky. First off, as noted earlier, the Inset was stuck in the Holder making it difficult to access the Holder itself. The same whacking technique eventually paid off, however. The Insert slowly started to move up in the Holder and the Holder up in the Case. I was eventually able to grab the top rim of the Insert with one hand and pull up on it while pressing the top rim of the Holder back down with the other hand, and the Insert pulled free. Then I could repeat the whacking to release the Holder assembly.

To get access to the terminal posts for the wiring along the top of the Holder you have to separate the upper Holder piece from its Lower Plates. The first step in this process is to remove the two wires connected to the Upper Holder at Positions 1 (single black trace) and 7 (single red trace). Position 1 is just a Terminal Screw and lock washer. Undoing the Terminal Screw at Position 7, however, also releases the Contract Spring for the Insert Case mounted at that location. Don’t lose it.

Then you can turn the Holders assembly over and remove the two RH Screws top and bottom that hold the two parts of the assembly together. The Holder can then be lifted away from the wiring. This time, as you can, see in the photos, the Holder came away in two parts, so I had to dig out a complete replacement Holder assembly. That was annoying enough, but the real mystery was finding a Jumper Wire running from Terminal 1 up to Terminal 4, for the Relay. That made no sense as it would turn the Relay Circuit permanently on, which was what was happening with this particular Headgear. Note in the third photo, this Jumper Wire is typical white loomed with a red/black tracer, typical of 19-Set and 52-Set production.

This discovery meant I had to open up the other Headgear Type 10, that was working just fine, and see what was going on inside it. In the last two photos, you can see this particular Jumper Cable was a solid black plastic loom, more typical of late war production. This Jumper Wire connected Terminal 1 to Terminal 3, which made much more sense and actually resulted in a fully working Headgear assembly. So when I started transferring the wiring from the broken Holder to the new replacement, the Jumper Wire was repositioned to Terminal 3 at its top end. That process was started in the third photo today, with the clear view of the Jumper Wire.


David

[David Dunlop]

If you look back at the second last photo in Post #715, you will see a good view of the upper backs of the two Contact Spring Assemblies in what I am referring to as the later version of the Type 10 Headgear. Notice the complete lack of rubber pads on the upper ends of the back of the Contacts. That initially puzzled me until I spotted the upper rim of the Insert. It had a half inch wide by 1 and a half inch long piece of black plastic hanging from it, that was originally centred behind the two Contacts. When I lifted the Insert out, this plastic strip fell away completely. The Insert in the broken Holder from the ‘Earlier’ headgear with the black rubber squares showed no sign of a plastic strip ever being applied to it.

I tested all the Inserts I had on hand and found the range of resistances between the centre terminal on the bottom and the case was from 42 to 47 Ohms and they all seemed in good working order. As I noted in an earlier Post, the Insert should be a snug fit in and out of the Holders, with just enough resistance from the two case Contacts on the sides of the Holders that the Insert does not wiggle and the bottom Contact Spring resistance will still push the Insert up a bit in the Holder. There should be no wiggle laterally. If there is enough wiggle, or an Operator thinks the backs of the two vertical Contacts must touch the case of the Insert for some reason, the Insert will fail to respond, as it should when the Pressel Button is pushed down. The Insert will probably appear dead.

If the fit of the Insert in the Holders is too snug, as I discovered in mine, a whole new problem develops. When the Insert is forced down into the Holders, it will transfer a load through the side Contact Springs into the Bakelite body of the Holders. If the Microphone gets banged around or dropped, that shock will transfer directly to the Bakelite and crack it. When I looked at the crack on mine, it was full through with rust dust, so had been broken for a long time.

When I had the Side Contact out from Terminal 7 to install a new Holders Assembly, I took advantage of the opportunity to adjust it for better tension. You can do this by placing the end the Mounting Screw fits through, in the jaw flats of a pair of Needle Nose Pliers and pressing the free end back towards the pliers. A few gentle attempts and you will reach a point where the Insert snugs in and out with your fingers just nicely. I also cut a new strip of black plastic Electricians tape to the correct size and fitted it to both Insert sides to avoid any future problems. Both Headgear Type 10 now work as they should, which was a big relief!


David

[David Dunlop]

The full description of this Gasket is as follows:

GASKETS, Cork, 1 & 55/64-inch OD, 25/32-inch ID, .031 inch thick ZA/CAN 5247

It fits between the upper face of the Insert and the back of the Microphone Cover to insulate the Insert from making any contact with the aluminum Cover that might cause the Insert to stop operating.

The attached photo shows the remains of one of these gaskets that is actually made of cork. The others I have are all either automotive gasket paper, or thin manila and one was actually made from a Canadian Armed Forces Shipping Tag, you can still read some of the sections of it on one side.

It can be a bit tricky getting this gasket to stay in place while you screw down the Cover and Rubber Gasket. I found the best way was to put everything in place and then run the four Cover Mounting Screws home about half way. Then, while pulling up on the cover with my left hand, I used a wooden toothpick through the Mouthpiece hole in the cover to move the gasket around until it was centred at the hole, lower the Cover and hold it in place while tightening the four Cover Screws. Job Done!


David

[James D Teel II]

Reference post 716. You say they both work as they should. Do you get side tone? As I said previously, mine seem to work with the exception that I can’t hear myself transmit. I’m curious if “working as they should” means a full transmission test.