Bias/Erase oscillator.

Back on top, the bias/erase oscillator PCB is retained by a single screw. This shows the board, it contains a pair of germanium transistors (one NPN, the other PNP) in a push-pull oscillator circuit. The screened cable soldered to the board carries the erase head drive (blue wire) and bias to the record/playback head (red wire).

Done