Mercedes: radio, alternator brushes, becker radio

Question
I have a 90 560 SEC and had to replace the original Becker radio.  I every now and then have a whining that matches the RPM when driving and listening to radio.  Any suggestions how to stop it?  Thanks

Answer
Hello Lola,
Just find a better channel to listen...Just kidding.
The whining is a signal caused by arcing in the alternator brushes, or in the ignition system. The arcing is normal in the alternator, so the signal need to be trapped.

Because the noise is intermittent I would look for a bad loose ground in the radio. The first place would be at the antenna or the antenna lead.

Make sure the antenna is secure against the fender. If it is retractable, make sure the mounting bolts are secure.The radio ground wire need to be clean and solidly attached to the body.
The next would be the power leads to the radio. Make sure that the negative and positive leads to the radio are clean and tight.
Finally, you can contact a radio install shop, or supply house,"Radio Shack" and purchase a noise filter. It will need to be installed at the alternator power lead.
Good Luck, let me know how it turns out.
Rob