Hi,
I would recommend you to check the grounding of each equipment and the
other reason might be capacitors changing values or bad connection
leads. I would like you to visit the link provided below :-
http://www.rane.com/note151.htmlIf the problem still persists, you need to send the unit for repair. To be honest, i would hesitate to get the unit repaired at a local shop.It is not easy to repair Bose. Had this been a different manufacturer, i would have able to advise you to seek a local repair shop or do it yourself. These units are complex and there is a need of service manuals. Moreover, it is not easy to repair these. Even if you find a local repair shop. i doubt if they would charge you less than what Bose quoted you for repair.
I wish i could have a better solution.
Let me know,if needed further assistance.
Hope i helped you.
Thanks for using ' Fixya ' and have a nice day!!
PS - Kindly accept the solution,if 100% satisfied from my response!!