Troubleshoot the Wonderbar


Quoted from the 1964 GM Radio Service Manual "Wonderbar AM-FM Automobile Radios and Reverberation Amplifier" (No copyright notice displayed.) Publication #PSD 53-102.



Automatic tuning is accomplished in the following manner:


1. The wonder bar is depressed.

2. The start switch closes completing a circuit through the stopping relay. The DS-46 Relay Amplifier starts to conduct and holds relay energized.

3. The stopping relay energizes and allows the governor to run.

4. The rack and worm gear is allowed to go toward the front of the tuner. The power spring pulls this unit forward.

5. The worm gear passes across the flat anti-backlash gears causing them to turn similar to the manual tuning operation and the pointer travels from left to right across the dial.

6. When the worm and rack reaches the front of the set, the "turn on" tab strikes the solenoid switch causing the solenoid switch to turn on. This allows the solenoid to energize, pulling the worn and rack to the rear of the tuner. This action stretches the power spring and returns the pointer to the low end of the dial. The pointer is pulled back by the treadle return spring. When the treadle bar strikes the "turn off" tab the solenoid switch is turned off and the solenoid is de-energized.

7. When the tuner is seaking and crossing a strong station, the Relay Amplifier transistor cuts off, the relay deenergizes, the governor stops, and the tuner stops.


Submitted by: Mike Frederick




Is there a motor that can be bad in the radio?


A motor? Heavens, no. It's FAR more bizarre than that. When you push the button, it uses a solenoid to simultaneously stretch a coil spring and move the tuner to the far left. I.e., it 'winds' the tuner. Then the spring tension is released to pull the tuner to the right. So that the tuner doesn't unwind all at once with a big *snap*, the scanning speed is controlled by a little gearbox/governor gizmo. One of the gears on the gearbox/governor is partially exposed to another solenoid, so that when you find a station, the solenoid latches the gear and stops the scanning.

When I fixed mine (it had the same problem,) the gearbox/governor thing was full of dust, hair, sand, etc., so I flushed it out with WD40. It now works fine on the bench (in fact, I just opened it up and ran it a few times just to remind myself of how the mechanism worked) but I haven't had time to implant it into my '67 yet.


It also quits playing sometimes, so I tap on the wonderbar and it will play again. Anyone with suggestions???


Yes, when it stops playing, tap on the wonderbar and-... *SLAP*

Oh, so that WASN'T the answer you were looking for?

I'd open it up (easy) and see if the problem is caused by the solenoid failing to 'wind' the tuner, or if the gearbox contraption is jammed and preventing it from unwinding, or if the latch solenoid is staying latched. That should point you to the solution -- which will most likely involve spraying WD40 and/or tuner cleaner (as suggested) on a sticking or dirty part.

The fact that it clicks when you push the button, but the dial doesn't move, suggests that it's not winding. It's probably because overcoming the grime friction is more than the winding solenoid can handle, but maybe the insulation on its wires have failed, or it might (sorry) be burned out. The audio cuts out because the latching solenoid is also a relay which is designed to cut out the audio while the tuner scans.


Submitted by: Dave Voorhis