26-04-2021, 02:01 PM
Hi all.
So, I've done a little more to this set, both the aerial frame coils were in a complete but sorry state: and I've now stripped dried and varnished the plywood former that the LW winding was on, the coil itself was still functional, but the form had shrunk over its ≈ 80 year life and the winding was loose to the point of falling off.
The original wire was single enamel but with a cotton or silk cover it was in good condition so I rewound it after the form was finished, thankfully, the coil had value of 1.76mH, same as before. This coil is mounted on the side of the set at right angles to the MW frame.
The MW frame coil is the reason that this set came to me in the first place, basically I was trying to find exact details if how they are made, as my other all dry Ever Ready had an inadequate lashup, and I was offered this set as a reference source: for which it has proved invaluable.
As I said the set was built as a 5216, meaning that it was a painted blue with black crackle finish, though this one had acquired a bad beige paint job. I asked a local furniture restorers opinion who said that it was acrylic silk emulsion and supplied me with some spirit cleaner that I've used to remove the beige abomination, and the back is now returned to the original, if worn in places, finish. I may just clear coat it if the rest of the set is as good condition, I think that a bit of life wear and patina is worth preserving.
The frame coil for MW on these earlier style sets (with a LW band), is fitted to the back of the set. In practice it seems it's a crummy idea, as the coil and the connecting wire is vulnerable to damage, but it is the original design so I wanted to have "my" set as built, and therefore copied this one, which needed the corner blocks re gluing and wire replaced.
As an aside, I had always wondered how it was that sets with a frame coil could be accurately aligned, but the ER has a clever if untidy method of adjustment. About a third of the final turn of wire is run loosely inside the frame coil to the terminal tag, this wire if moved to the middle of the back away from the rest of the coil lowers the inductance of the coil: if its run nearer the rest of the coil its inductance is increased, (at manufacture the final position was fixed with the aid of the staple gun in keeping with Ever Ready's high build quality standard!) It means that an adjustment range of ±10uH can be achieved. Clever.
Just in case anyone else gets stuck, the vital statistics for MW coils are as follows:
former depth overall (including ⅛" lip) 1½"
former width overall 11¼"
Former height 7"
Tuned winding 20 turns 0.5mm ø single silver plated ttfe insulated, (originally rubber over cotton covered copper single).
Aerial winding 1 turn 0.5mm ø ECW.
So, I've done a little more to this set, both the aerial frame coils were in a complete but sorry state: and I've now stripped dried and varnished the plywood former that the LW winding was on, the coil itself was still functional, but the form had shrunk over its ≈ 80 year life and the winding was loose to the point of falling off.
The original wire was single enamel but with a cotton or silk cover it was in good condition so I rewound it after the form was finished, thankfully, the coil had value of 1.76mH, same as before. This coil is mounted on the side of the set at right angles to the MW frame.
The MW frame coil is the reason that this set came to me in the first place, basically I was trying to find exact details if how they are made, as my other all dry Ever Ready had an inadequate lashup, and I was offered this set as a reference source: for which it has proved invaluable.
As I said the set was built as a 5216, meaning that it was a painted blue with black crackle finish, though this one had acquired a bad beige paint job. I asked a local furniture restorers opinion who said that it was acrylic silk emulsion and supplied me with some spirit cleaner that I've used to remove the beige abomination, and the back is now returned to the original, if worn in places, finish. I may just clear coat it if the rest of the set is as good condition, I think that a bit of life wear and patina is worth preserving.
The frame coil for MW on these earlier style sets (with a LW band), is fitted to the back of the set. In practice it seems it's a crummy idea, as the coil and the connecting wire is vulnerable to damage, but it is the original design so I wanted to have "my" set as built, and therefore copied this one, which needed the corner blocks re gluing and wire replaced.
As an aside, I had always wondered how it was that sets with a frame coil could be accurately aligned, but the ER has a clever if untidy method of adjustment. About a third of the final turn of wire is run loosely inside the frame coil to the terminal tag, this wire if moved to the middle of the back away from the rest of the coil lowers the inductance of the coil: if its run nearer the rest of the coil its inductance is increased, (at manufacture the final position was fixed with the aid of the staple gun in keeping with Ever Ready's high build quality standard!) It means that an adjustment range of ±10uH can be achieved. Clever.
Just in case anyone else gets stuck, the vital statistics for MW coils are as follows:
former depth overall (including ⅛" lip) 1½"
former width overall 11¼"
Former height 7"
Tuned winding 20 turns 0.5mm ø single silver plated ttfe insulated, (originally rubber over cotton covered copper single).
Aerial winding 1 turn 0.5mm ø ECW.
