the radio gets power from the amp
Appears to be correct, thanks Tim.
The diagram is showing the power coming from the "Cig & Radio" fuse into the Amp on
pin 7 of the connector as "Acc". I would suggest checking the fuse, but the head works, and they appear to be on the same fuse.
I'm was thinking of it working like my Pioneer Head/Amp. Where, the Amp has power to it all the time through a direct wire (a "+B") to the battery (fused). It also has a second wire (an "Acc")from the Head, but the Amp doesn't actually "power up" until it sees voltage on the "Acc" wire from the head. When it does, it then draws its power through the "+B" wire. So, that's why I'm thinking that the "Acc" acts as the trigger to power up the amp.
Studying the diagram some more, maybe the "Acc" just passes through the Amp to the Head and then the "+B" in their diagram is the trigger for the Amp to draw it's power from A 7 & 16 on the Dome fused line (w/a 20 amp fuse vs the 15 amp cig & radio fuse).
I still think the 'Beep" wire is to trigger the "Beep" sound which the System 10 generates. That is a generated tone. If the head generated it, there would be no need for a "Beep" wire.
OK, scanned the diagrams.
This morning I was looking mostly at the connection between "S-8" and "r 5" connectors.
Notice in the "Service Hints", it shows:
A-7, A16 -Ground,
Always Approx. 12 volts.
B7 - Ground, Approx 12 volts with ignition on (or ACC position)
The first one is going through the "Dome" fuse. Does your Dome light work?
My want to verify: "A-7, A16 -Ground, Always Approx. 12 volts."
And, the 12 & 13 pins have ground continuity.
Since they show A-7 and A16 as "Always Approx. 12 volts", and the other as "12 volts with ignition on (or ACC position)" this would seem to fit into how I "Think" it works. I don't actually know for certain.
Andy