I just finished installing the factory am/fm radio in my 65 chevelle after it's restoration. I am getting a high pitched noise through the speaker (alternator? Ignition?) when the engine is running. I have installed a power line filter and an antenna filter to no avail. In the factory assembly manual, they show a capacitor going from a terminal on the voltage regulator to ground. It is missing on my car. Could that be the culprit? Where can I find one if it is????