I have a couple old radios now, and I didn't know if they worked. Despite very little electrical knowledge I came up with a ~$20 bench test rig that requires no soldering, no car battery, and no multimeter. Maybe this will help someone else. Details on my blog.

The price of any radios I have for sale or trade has now just doubled (i.e. "tested working!")
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We still have analog AM and FM stations? I thought that was long gone.

Yes.. all radio is analog, and that sends out the digital sync up signal. If the radio is capable, it switches to digital. If not, it just keeps the analog signal. So your old AM and FM radios still work.

Clay

I'm not sure I have listened to the radio since my 914 was new. Once the tape player was an option in cars I never used the radio again.

Even if you don't want to listen to radio via the analog waves, you can still confirm that the radio and internal amplifier are working. Then plug your mobile music player into the aux port. I believe a 6-pin DIN (male) to 3.5mm adapter would be all you need for the Frankfurt.