squealing speaker??? in a 200

[james accordino]

I finally got a working radio with the code (Thanks
Stott!) for my 89 200.  It's a Delta.  After I plugged
it in and turned it on, the rear speakers-actually
maybe just the left one, started a continuous
high-pitched squeal.  Very loud and very annoying.  I
isolated it to the bottom plug group.  That's the one
that supplies #30 track power to the radio and rear
speakers.  There are 2 white, 2 red, a gray/blue wire,
a white/blue and a brown wire.  Any ideas what this
might be?  I know the radio works fine, and I was even
able to code it correctly, but the squeal persists.  I
know I'll figure it out eventually, I just thought
someone might KNOW what this is.

Thanks
Jim Accordino