Have a B&O Budd car set, 30-2144-1, proto sound, that has a buzz coming from the speaker. When initially powering up at about 5-6 volts there is no buzz, advancing the throttle to between 9-11 volts the buzz comes on, disappears, comes on again. I understand this is a voltage regulator problem. Have tried different speakers and volume pots, same thing.
Trouble shooting this is not covered in our Service Manual. Can someone enlighten me as to what voltage regulator it is and the Digi-Key part number?