Becker Mexico Sound System Inquiry--how to test

I have a 70's vintage Becker Mexico AM-FM-cassette unit that I'd like to bench test. It has a "loudspeaker" module connected by a multi-pin
plug. The back of the main unit has an antenna jack and another smaller multi-pin jack, with 8 positions.
One black wire leads from a small box on the back. Another multi-pin jack appears, with five positions arrayed around a center position; it is covered with a polyethylene cap containing a jumper that connects two pins.
Damn-! This ain't no Delco!! I need help.
The label on the unit reads:
"Mexico Cassette Vollstereo 485 Gerat Nr. 2002151"
**Can anyone suggst where I might download a wiring diagram for this thing-? Pdf file, maybe-?**
Thanks, Danke, Buzzy
PS----I no longer have the old Mercedes from which this radio was pulled. I'm contemplating placing it in an old Volkswagen dash.
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It is not this complicated. Black wire = 12V ignition line Chassi = Ground Power pack black and white socket = 2 x speaker outputs power pack spade connector = antenna trigger
- they should be

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