Radio or speaker problem

[Mike Arman <armanmik@n-jcenter.com>]

>Subject: radio or speaker problem
>
>Yesterday--suddenly (things gotta start sometime, I suppose)--the Bose
>stereo system (in '91 200q) began emitting a thundering, low-frequency
>noise (thump-thump-thump-....). At first I thought something in the
>drivetrain had crapped out. The noise went away for some minutes, but now
>it's there almost as soon as (and whenever) the radio is turned on (makes
>no diff whether AM, FM or CD). It has a deafening intensity--even at the
>lowest volume setting. All connections at the back of the radio look OK.
>
>Any ideas?
>
>

This noise is called "motorboating" and usually appears when one of the
power supply filter capacitors has gone open. This applies to AC-line
powered radios, and I don't know what's inside the Bose - it might have an
inverter and some rectifiers if anything in the radio needs more than 12
volts.

It isn't a speaker problem - sounds like a bad power amp chip if it is on
one side or one end of the car only, but if it is everywhere, it's the
power supply.

Upgrade time . . . (boo!)

Best Regards,

Mike Arman