As I worked today at the Retro Electronics Store where I help out two days a week I came across a box of metal cylinders with four pins on one end. They looked like this:
They were called car radio vibrators and they came from another age. I immediately remembered my first car, a fairly beat up 1957 Chevrolet and its radio. Cruising around was great fun but it was even better with the radio blaring out the tunes of the day. The radios that were being used at that time had not yet come into the new transistor age. They had tubes and tubes require a higher voltage to operate properly than do transistors. The problem was how to get the required 100 to 200 plate voltage from a six or twelve volt car battery. The Vibrator was the answer to this problem.
When I wanted to listen to the radio I would turn it on. The dial light would illuminate immediately and there would be a soft hum (the vibrator at work) and ten to twenty seconds later the sound would be available. Tubes had to warm up before they would function properly.
When I first tried to get this vibrator to work it would not start. Eventually I gave up on banging on it and got out the cutters and removed the case. The contacts were very badly surface corroded. It was as if they were coated several mils thick with a white oxide powder. I went to work with some fine sand paper and after about a half hour I finally had the contacts making good contact. I wanted to hook the vibrator up to a center tapped 6.3 volt secondary of a transformer and see what level of voltage would be generated on the primary of the transformer. Here are the internals of the vibrator: The black on the end closest to the bottom is a coil with one magnetic pole near the switch throw which can swing back and forth between the outer contacts.
Here is a schematic of the simple circuit that I wired up using the vibrator to generate 200 + volts AC:
The vibrator itself is a single pole double thrown switch with a center off position when it isn't powered. The coil of the vibrator sits across the power and one side of the switch. When power is applied the magnetic field of the vibrator coil causes it to deflect but as soon as it does the contacts energize one side or other of the center tapped transformer. The counter EMF of the transformer causes the coil to reverse polarity and jump back which causes the other side of the center tapped winding to be energized. This process continues for this unit at a rate of about 600 Hz output. The transformer which is usually 115 Volts primary and 6 volts center tapped secondary now takes the fluctuating 6 volts on either side of the center tapped secondary and transforms it to 200 volts plus on the primary winding.
I took a short video of the unit in operation. Apologies for the poor videography.
As soon as transistors became available in car radios in the early 1960s this technology was quickly obsoleted. I was hoping that the contents of the box that I found might be of interest to the rebuilders of old cars but after my experience with the corroded contacts I feel that it is unlikely that any of the units in the box are still functional after the 50 years since they were manufactured. Of course there is always the possibility of opening the case and filing the contacts just as I did but this unfortunately doesn't leave the unit in a very pretty condition.
John
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