For the last week I have been messing around making a "look-alike" of a 1939 Little Maestro, I hasten to add "look-alike" as I am not certain what the original radio was that the cabinet I am using came from, but it is very similar to a Pilot Little Maestro. (does anybody recognise the cabinet with its 3 control holes, one spaced out to the left.)
I have used the cabinet before, some of you may recognise it from the original Vrat Minimalist Superhet Radio project.
This version is going to be used for 1940's wartime military "exhibitions" and displays, and will play some music and radio programs of the period via either a Bluetooth or FM transmitter from an Iphone. In order so it can run all day off readily obtainable batteries it is now going to be a "Minimalist" transistorised radio.
The radio module happened to be in a spares draw. It is based on a Toshiba TA7613AP radio IC.
The 300mW audio output seems to have more than enough volume when just turned down a little from the onset of distortion. It is feeding into a 4 inch 6 ohm loudspeaker.
I cant remember where the little radio module came from, but it may have come from a clock radio that I dismantled.
Rather than making slats to go over the speaker opening I used some old speaker cloth, that looks like it is woven from twisted raffia and looks fairly in keeping with the period.
I knocked up a small wooden chassis to mount the circuit board and controls on. At a later stage I added an extension in order to add the volume control and battery clip to the same chassis board.
We designed and "printed" an drive drum adaptor to fit onto the existing tuning thumb wheel, with posts to terminate the ends of the drive cord on, and I dismantled an old potentiometer with a broken track from a KB 333 to get the fixing nut and bush with spindle. The end of the spindle was turned down to make a capstan shape. It ended up lot smaller diameter than intended as the bakelite on the end I was machining disintegrated leaving just the ¼ inch spindle. This worked out fine in the end, it gave a nice and smooth operation with a 10:1 reduction.
Another duff potentiometer was found and used to get a drive spindle for the wave change switch. This was a fiddly job and took several attempts to get it to work as the slider switch would not operate if pushed from the end of an extension fitted to the switch slider. In the end I used an intermediate lever/pivot to operate the switch.
David kindly sent me some images of a Little Maestro dial and this has been edited, and resized to fit the slightly taller aspect ratio of the cabinet I am using. The final dial will be printed on a colour laser printer when Sam goes back to work.
I made a couple of runners to slide a Perspex dial glass into and Sam printed a new dial pointer to be a push fit into the centre of the new capacitor drive adaptor we made.
It wasn’t planned, but I had to cut a large round hole in the trial dial as it soon became obvious on assembly that it was impossible to fix the drive cord to the drive adaptor.
Anyway it is all working and now just needs the final dial to be printed and glued in place and possibly a back made for the radio.
I hope nobody will notice that the wavelength markings on the dial will be reversed.
Mike
I have used the cabinet before, some of you may recognise it from the original Vrat Minimalist Superhet Radio project.
This version is going to be used for 1940's wartime military "exhibitions" and displays, and will play some music and radio programs of the period via either a Bluetooth or FM transmitter from an Iphone. In order so it can run all day off readily obtainable batteries it is now going to be a "Minimalist" transistorised radio.
The radio module happened to be in a spares draw. It is based on a Toshiba TA7613AP radio IC.
The 300mW audio output seems to have more than enough volume when just turned down a little from the onset of distortion. It is feeding into a 4 inch 6 ohm loudspeaker.
I cant remember where the little radio module came from, but it may have come from a clock radio that I dismantled.
Rather than making slats to go over the speaker opening I used some old speaker cloth, that looks like it is woven from twisted raffia and looks fairly in keeping with the period.
I knocked up a small wooden chassis to mount the circuit board and controls on. At a later stage I added an extension in order to add the volume control and battery clip to the same chassis board.
We designed and "printed" an drive drum adaptor to fit onto the existing tuning thumb wheel, with posts to terminate the ends of the drive cord on, and I dismantled an old potentiometer with a broken track from a KB 333 to get the fixing nut and bush with spindle. The end of the spindle was turned down to make a capstan shape. It ended up lot smaller diameter than intended as the bakelite on the end I was machining disintegrated leaving just the ¼ inch spindle. This worked out fine in the end, it gave a nice and smooth operation with a 10:1 reduction.
Another duff potentiometer was found and used to get a drive spindle for the wave change switch. This was a fiddly job and took several attempts to get it to work as the slider switch would not operate if pushed from the end of an extension fitted to the switch slider. In the end I used an intermediate lever/pivot to operate the switch.
David kindly sent me some images of a Little Maestro dial and this has been edited, and resized to fit the slightly taller aspect ratio of the cabinet I am using. The final dial will be printed on a colour laser printer when Sam goes back to work.
I made a couple of runners to slide a Perspex dial glass into and Sam printed a new dial pointer to be a push fit into the centre of the new capacitor drive adaptor we made.
It wasn’t planned, but I had to cut a large round hole in the trial dial as it soon became obvious on assembly that it was impossible to fix the drive cord to the drive adaptor.
Anyway it is all working and now just needs the final dial to be printed and glued in place and possibly a back made for the radio.
I hope nobody will notice that the wavelength markings on the dial will be reversed.
Mike