PET power supply questions

I thought that the Motor-On signal was just a swtich to ground inside the tape recorder that signaled to the PET that the play or record keys had been pressed. IIRC it goes to a TTL-level input somewhere. It's independant of the actual motor control circuit, which IIRC is a power transistor connecting the unregulared 9V line to the motor. About 20 years ago (is it that long???) I built an interface between a PET casstte port and a Radio Shack tape recorder, The recorder i used had the useful design feature that the internal power switch (operated by the keys on the recorder) was 'before' the remote control socket. That means I could use a relay conencted to the socekt to control the motor (relay coil driven from the motor drive output on the PET) and could sense the power voltage on one side of that socket wrt ground (outside of the audio sockets) to determine if the keys were pressed. So my interface worked just like a real CBM tape unit. I should still have the scheamtics, etc for that, but they will take some finding... -tony