1960 Wonderbar Motor Noise

[Joe M.]

Re: 1960 Wonderbar Motor Noise

I will try attaching a ground wire from the generic antenna to the radio ground wire and then ground to the frame. Thank you for the info.

[Jim L.]

Re: 1960 Wonderbar Motor Noise

He said the noise was still present even with the antenna disconnected. That strongly suggests the noise is being conducted rather than being radiated.

And since the noise has been present since the on-off switch was replaced, I'd look at it first to see what changed.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

Grounding the generic antenna had no positive effect. I will test the condensers next.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

The condensers tested good as I suspected they would. Everything now points to an internal radio issue that does not show up during a bench test. The radio works great when bench tested or tested in the car without engine running. Now my dilemma, who do I send the radio to that can figure this problem out? I have been unable to contact Charles Siefried. There are numerous Wonderbar "experts" on the Internet.

[Jim L.]

Re: 1960 Wonderbar Motor Noise

You aren't going to give the vendor who rebuilt the radio a chance to make it right?

[Joe M.]

Re: 1960 Wonderbar Motor Noise

No. I just spoke to another Wonderbar repair man and he said that there is a 0.5 mf capacitor connected to the on/off switch that may have not been re-connected when the switch was replaced, but he said that capacitor would not reduce a loud roar like my radio is generating. He suggested that I purchase a 0.47 mf capacitor with axial lead or a radio lead and connect it to the power wire and ground to the radio case and see if that reduces the noise level. He doubted that it would reduce the loud roar as they are not designed to reduce high engine noise.

[Dennis C.]

Re: 1960 Wonderbar Motor Noise

I am wondering if a bad distributor ignition condenser maybe the multiplying your house condition?

[Jim L.]

Re: 1960 Wonderbar Motor Noise

No. I just spoke to another Wonderbar repair man and he said that there is a 0.5 mf capacitor connected to the on/off switch that may have not been re-connected when the switch was replaced, but he said that capacitor would not reduce a loud roar like my radio is generating. He suggested that I purchase a 0.47 mf capacitor with axial lead or a radio lead and connect it to the power wire and ground to the radio case and see if that reduces the noise level. He doubted that it would reduce the loud roar as they are not designed to reduce high engine noise.

It's "radial" leads and the lead configuration doesn't make any difference.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

Thank you Jim.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

I haven't tested the distributor condenser. Wouldn't a bad distributor condenser affect the engine running smoothly? The engine starts, idles, and accelerates great. I will test that condenser next. Thank you for the info.

[Jim L.]

Re: 1960 Wonderbar Motor Noise

I haven't tested the distributor condenser. Wouldn't a bad distributor condenser affect the engine running smoothly? The engine starts, idles, and accelerates great. I will test that condenser next. Thank you for the info.

The condenser inside the distributor affects engine operation only. It doesn't play a role in electrical noise suppression.

[Dennis C.]

Re: 1960 Wonderbar Motor Noise

I wasn't suggesting that it did suppress noise. I was wondering if a faulty distributor might be causing excessive noise.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

Great question Dennis. I hope Jim responds.

[Jim L.]

Re: 1960 Wonderbar Motor Noise

I've been trying to imagine how component degradation within the distributor could increase ignition noise. I'm of the opinion that, if anything, the noise would decrease. Follow my reasoning.....

If any conductor (wire, point contacts) develops resistance, coil current decreases and noise would go down.
If the condenser were to become leaky, the coil/condenser oscillations would be damped out more rapidly and noise would go down.

Of course any catastropic failure.... broken wire, points shift and stop opening/closing, open ballast resistor, etc, .... engine stops.

This said, you've done experiments which indicate your radio is being plagued with noise being conducted through the vehicle wiring as opposed to being radiated through the air. Too, the noise started when you had one specific repair performed on the conductive path into the radio.... the on/off switch was changed.

If it were mine, I'd open up the radio to see what was really done (or, more likely, not done).

[Jim L.]

Re: 1960 Wonderbar Motor Noise

I found an on-line schematic for a '60 passenger car Wonderbar radio. I bet the circuit is substantially identical to the Corvette radio.

The passenger car schematic shows a .47mF capacitor between the 12V input and ground. Following that it appears there is a feed through capacitor (odd symbol.... I'm half-guessing what it is) of unspecified value, then the switch, and then a series choke. Your radio should be the same.