Wireless Set No. 52 Canadian - Project

[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