While rummaging through some more wireless bits boxes on the weekend, I rediscovered an old project package I had abandoned umpteen odd years ago, Trying to put together the really good parts from several Key & Plug Assemblies No. 9 Canadian, to make a good one for one of my 19-Sets. I think I stumbled across a very good assembly at a local sale and work on the project halted.
As it turns out, one of these Key and Plug Assemblies is needed for the 52-Set, and since I cannot do any soldering until my new soldering station arrives, I decided to reactivate the work needed and put a Key & Plug Assembly together for the 52-Set.
The project was simple enough, involving the transfer of the plug and cord assembly (in good condition) from a scruffy unit somebody had cut the leg straps from, to a very good unit somebody had cut the plug and cord from.
There are only two things that are a bit tricky about the work needed to be done: the two terminals on the positive and negative cord leads are crimped to the leads AFTER the cord is fed through the grommeted opening in the key base plate at the factory and they are too wide to slip back through the grommet as is, and secondly, there is an anti-strain loop woven into the cotton cord loom that slips over a J-Post Bracket at the back of the key bar assembly, just inside the case, This cotton loom is now some 60+ years old and is often not up to liking a lot of pulling and tugging, without breaking.
Step one is to remove the two terminal screws for the positive and negative leads. Make note the negative (earth) lead is the front most one. It has green cord wrapped at the base of its ring terminal and a green tracer woven into its loom. The line directly behind it is the positive one, with a red cord wound at its terminal lug and a red tracer woven into its loom.
Once you have removed the two leads from their terminals, remove the terminal screw on the back of the J-Post. It is only there to secure the anti-strain loop that has been slipped over the post. You will have to feed about one more inch of the plug cord into the key assembly at this point to give yourself enough loose cord for slipping the anti-strain loop off the J-Post. Once it is free, you just have to deal with the two terminal ring lugs.
The best way to remove the two leads is to hold a ring terminal with a pair of pliers, on one side of the lug, about one third of the way across the ring, Then take another pair of pliers directly across from the first and GENTLY and SLOWLY bend the ring to form a gradual, near 90 degree bend. You just want the diameter of the ring to have reduced enough to slide out through the metal grommet. Do the same to both ring terminals and you should then be able to remove the plug cord from the key assembly. Best to do it strain loop first and then one electrical lead at a time.
Reverse the process into the good key assembly. Insert enough cord that you can easily slip the anti-strain loop over the new J-Post and then gently snug it back. To reflatten the two ring terminals, I use a pair of needle nose pliers that have a smooth inner face to the jaws down near the jaw pivot point. Or, I sneak a pair of Debbie’s jewellery pliers that have smooth faces to do the job.
A couple of other points on these Key & Plug Assemblies. I have seen them with and without the bakelite guard fitted to the key bar, under the bakelite knob. I am not sure if this is just a case of these guards sometimes ‘disappear’, or if it reflects a change in production, with early morse keys lacking the guard and it being added later. No big deal if you never plan to use the key, If you do plan to use the key for CW work on a restored wireless set, I highly recommend you find a guard and install it.
Ever noticed the funny looking bakelite finger guard surrounding the morse key socket on the Mk III 19-Set? It is usually not there on the Mk II Set, which normally has either nothing, or a simple flat rectangular bakelite plate around the socket.
When you are working CW on a wireless set, the Send and Receive functions are controlled by the key plug. Fully inserting the plug places the set into transmit mode, pulling the plug half out of the socket places the wireless into receive mode. In Receive mode, one half of the brass plug assembly sits exposed outside the front panel of the set. If the wireless operator is in a hurry to transmit and pushes the plug back in with his fat fingers in the way, he will find full transmit High Tension power arcing into himself very quickly. Hence the development and installation of the finger guards. And the guards are great, but not perfect. The one on the Morse Key Bar and the knob will only protect you for the first 8 Amps. After that you are on your own.
Wonder how many wireless operators had their key strapped to their thigh first thing in the morning and spilled their cup of tea on their lap? Be more than their Rice Krispies going ‘Snap, Crackle and Pop’.
Hope this wan't too long winded.
David
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