Nissan Repair: Nissan Bose Audio System, field effect transistor, nissan bose

Question
I have a 93 Infinity Q45 with the stock Bose audio system.  Out of nowhere it has started this high pitched whine much like feedback.  This is independent of the radio volume.  I have switched out the head unit and the sound remains.  Any suggestions?

Answer
Rus,

The speaker with the noise has a blown amp.  Each speaker has an amp and when they go out they make noise.  The part that fails is either a capacitor or a field effect transistor.  If you take the amp card out you will see a burnt up black thing with three leads or a can that is leaking.  Check out the internet as there are several places to get parts or the entire card if soldering is not your thing.  About a hundred bucks for an amp card.