Repairing the "Magic Keyboard" on a Stewart Warner

There's not really much in the magic keyboard on a Stewart Warner (model 03-5S1). It's just a push button station selector. It works pretty much the same way as other push button selectors except that it has a different way of tying the button shaft to the tuner shaft. It uses some kind of material that's sort of like an oil paper, but it's made of cloth; like canvas, but thinner.

Reminds me of the old, aged, window shade material before they were made of plastic. On this beautiful radio (after restoration), two of the push buttons didn't work because of failure of this aged material.

Here's the mechanism. Click on the pictures to see the strips of material. They are made of two strips joined together by rivets pushed through brass spacers.

Here's the torn material. Notice the brass rivets holding the strips together.

The brass rivet has to be driven out of one of the brass spacers to release one end of the flexible strips. I used a punch made from heavy gauge piano wire from the hardware store and a strip of wood to support the mechanism so it wouldn't get bent out of shape during the pounding. Otherwise, the pulley on the right end in the photo would have been bent on it's shaft since the mechanism lays on the tuner on the left and the pulley on the right.

These strips of material are riveted, two ends together, so that they make a loop. Here, both rivets have been driven out, and the outboard brass spacer has been removed by carefully prying open the surrounding arms that hold it in place.

Here's the punch, the brass spacer, one half of the torn strip, and the board with a hole in it, which is used so the rivet can be driven out without putting the spacer into a vise that could damage it.

Here's another view of the spacer and fabric. Where the fabric is riveted into the spacer, there is a bit of reinforcement material added to strengthen the union.

I looked everywhere around the house to find a similar material to use to make new strips, but to no avail. Then I happened to notice that a canvas bag in the wife's closet looked pretty close to the right thickness, weave, and flexibility. I decided to perform surgery.

Here's the new fabric strip marked out with microscopic precision. (sort of) The strips should each be about two inches long. Measure your original strips to make sure. Your's might be different. (Shorter strips rather than longer work better. They stretch a bit afterward, making the mechanism action a little loose. If it's loose, it won't stop exactly on the station.)

Make sure you put the bag back in the closet after the surgery. Act dumb if your spouse questions you about the hole in the bag.

I wanted to make sure that the threads in the fabric didn't separate, so I coated the strips with tacky fabric glue.

Reinforcements for the riveted ends were cut out of manila card stock.

The ends of the fabric were perforated with an awl to make the hole for the rivet. Punching the hole would have cut the threads of the fabric, weakening it. The reinforcements were glued to both sides of the overlapped ends with fabric glue, and the rivet was pushed through the hole into the brass spacer. (The rivets aren't "set". They are just force-fit into the spacer making it easy to reassemble.)

Rather than try to drive the rivet home in the spacer and take a chance on clobbering the mechanism, I used a nifty parallel jawed pliers (Ace Hardware) to squeeze the rivet into the spacer. Any large size pliers should work.

Here is the mechanism with two of the loops replaced. After working the mechanism several times to see if my work would hold up, another of the loops broke, so I decided to replace all of them. Evidently, they were all weak from age.

Here's the mechanism mounted on the chassis, shown from the back after replacement of two of the loops. (This is where I broke the third one.) I replaced the other two loops after this picture was taken.

The stations are set using this procedure: Loosen (unscrew) one of the buttons. While pressing the button down, tune in the desired station. Still pressing down on the button, tighten it by turning it clockwise. Do that for each button.

How does it all work? The upper part of each loop is attached to the tuning shaft itself, so it can rotate with the shaft. The lower part is attached to the brass spacer which can rotate within a saddle shaped cutout. This spacer is held in place by the inner "U" shaped steel part, which is attached to the button shaft. When the button is pressed, the shaft pushes the inner "U" down, taking up all slack in the fabric loop. When this happens, the spacer bottoms out within the loop and the loop pulls the tuning shaft as far as it was when the button was set on the station.

It was a lot of work, but satisfying to know that the radio is completely restored now.

Too bad the "Magic Keyboard" doesn't work as well as other tuning mechanisms. It rarely seems to hit directly on the station the button is set to. Maybe the metal parts are worn, or maybe it never was very good to start with.

Still, it's complete now. I like the way the buttons sit in the recess cut into the top of the radio.