Re: Wonderbar Radio funtion

Posted by HH56 On 2016/7/5 19:02:57

I have a 55 schematic but don't have a 56 Wonderbar schematic to see if there is any difference in polarity of caps vs the 55 unit. It would be interesting to compare closely and see what if any difference there is. I know some radios do not really care because the electronic components are referenced to voltage and ground internally and don't care about any external influence. That can be verified by all the cars with batteries that accidentally get switched by mechanics or whatever and the radios keep right on working.

The radio works essentially all on DC. 12v is fed to the tuner unit into the on/off switch and also directly powers the dial light, solenoid, relay and tube filaments. The switched 12v is also fed to the speaker and power unit. The vibrator takes that 12v and starts oscillating. With the use of a center tapped transformer, the vibrator energizes one half of the transformer primary and then the other half in rapid succession. The vibrator is running at 115cycles so with the transformer primary alternating sides it starts mimicking AC. The secondary side of transformer feels the "alternating" primary and puts out a voltage of 280 VAC. That voltage is fed to a rectifier tube and comes out as a positive 255V DC which is fed to the rest of the radio.

As that video explained, there is no motor in the unit. When the needle moves, a spring pushes the mechanism and thru some gears and a flywheel the speed is controlled. There is a relay which either releases a stop to let the flywheel go or shoves the stop into the flywheel to block the rotation. When the mechanism reaches its end a switch is tripped and a solenoid pulls the mechanism back and compresses the spring again -- sort of like the way the clock winds itself.