Christmas 2013 yielded many fun gifts, but one in particular was highly unexpected. On my yearly DiDonato Christmas list, I had included a stand upon which I could shine my shoes. To some this might seem a very odd request, but growing up I had always admired Dad D’s shoe shining kit. I remember the biting smell of shoe polish and the unexpectedly loud whir of his Ronson Two Speed Roto-Shine shoe polishing motor.
I wasn’t looking for anything as elaborate as his – just a stand upon which I could apply elbow grease and achieve new levels of luster on my work footware.
You can imagine my surprise when Dad D procured for me my very own Ronson Two Speed Roto-Shine Shoe Polisher!!!
DAAAAANG! HOW AWESOMELY RETRO!
There was, however, a problem. Only the high-speed was working. Dad D and I took the motor apart and found a fairly simple design.
The switching mechanism switches between two different circuits. One of the two circuits provides a direct connection of line voltage to the motor: Full Speed. The second does the same, except there’s a resistor in the path. This is unsurprising. The Resistor limits the voltage going to the motor. If that resistor fried, then the circuit wouldn’t work.
When we tested the resistor with an ohm meter we got nothing. This suggested deadness. Unfortunately, the resister was really weird looking. It didn’t have the traditional color scheme… but being that the unit was from the 50’s, we didn’t think much of it. Still, we had no way to determine what the value of that resistor was.
I decided to enlist an electrical engineer to aid in the process.
Sander and I took a look at the circuit. I told him about the weird resistor and he too agreed that it was weird. “Simple solution!” Sander declared as he pulled a potentiometer from his grab back of electrical goodies, “We’ll use a pot and gauge speed by the sound of the motor.”
And that’s what we did. But the results were somewhat surprising. Figuring out the resistance was easy – but when we tried the unit with various resistors they immediately burned up. Huh?
Sander figured it out in a stroke of obviousness. Despite my insistence that this was an ancient resistor – it was no such thing. The device was a Diode. How Clever!
The diode cut out half the waveform and reduced the speed of the motor by half. By doing so, the designers were able to get away with a much smaller device within the body of the polisher.
We replaced the diode and later that night I shined my shoes to glorious levels of sheen.