The 1958 Mercury sales manual announced that the radio for 1958 was partially transistorised and consequently used no vibrator and rectifier.
This was a major step forward for car radios and was possible thanks to the development of transistors. The only valve in a radio that requires really high gain is the audio output valve. To get high gain the valve needs a full +250V on the anode. The only way to get +250V from the 12V DC car circuit was to convert the 12V DC to 12V AC square wave with a vibrator, which is a mechanical switching device, then step the 12V AC up to 250V AC with a power transformer and then convert the 250V AC to 250V DC with a rectifier. This was all very cumbersome but worked fairly reliably. Once transistors came along, the audio output valve could be replaced by a power transistor, the remaining valves could use +12V directly from the battery on their anodes and the vibrator, power transformer and rectifier valve could all be eliminated. This made the circuit much simpler and more reliable. It's little wonder that car manufacturers were very quick to implement the new technology and proudly announced the improvements to car radio design.
When my car arrived and I took the radio out to repair it, I was intrigued to see that it was a vibrator circuit design, contrary to the sales specs. Why had my car a different radio ? The radio certainly didn't look like it had been replaced by an older model. I looked up the model number on the Internet and found that it was a 1957 Mercury radio. What was a superseded design of radio doing in my car ?
Here is my guess. In those days most accessories were installed by the dealer. We suppose that the dealer who sold the car had a stock of radios left over from the 1957 model year and wanted to get rid of them. So either he installed the superseded radio in the car unknown to the buyer, or he offered the buyer a discount on the price of the radio if he would have the older model. We suspect the latter since it should have been obvious to the buyer from the buzzing of the vibrator that he had an old model. But on the other hand an inattentive buyer may not have realised he shouldn't have been hearing the vibrator buzz.
