Sony CFS-FM7 mini boombox with Sony SRF-7 service fm stereo receiver

Finally, a direct question that I can answer. The tuning string inside the radio only tunes the AM radio. The FM tuner is tuned electronically by way of the electrical connections on the bottom of the blue FM module. However, when you remove the FM module, you can then tune the FM on the blue module by rotating a mechanical knob like you normally would on most analog FM radios. The tuning string has absolutely nothing to do with the FM radio that you insert and or remove from the main unit.

 

I believe that white and red wire connects the tuner to the portable tuner electronics...