'91 100 Bose Issues

[wadd-wadd at usa.net]

I am getting the following symptoms when I hook up a known good Bose unit to
my '91 100. 

Only the front driver door speaker works after it emits a lot of static. Then
it settles and I hear the radio. No other speakers work.

Any advice on where I can start to troubleshoot my Bose system?

Thanks.