I need the schematic for a Blaupunkt "Frankfurt" (no other model ID) car radio made in Japan, probably built in the late 70's - early 80’s. It is AM/FM stereo with an "ARI" interface. The antenna is on a "dongle" and so is a 6-pin DIN connector. It also has a multi-pin male connector on the rear. AM, FM and DNR controlled by alternate-action pushbuttons mounted vertically, at the right side of the tuning dial. Have contacted Blaupunkt corporate in Germany without success. Can you help? Thank you, Bill