Has anyone any experience with is unit , is the motor adjustable , and if so how the heck does that grey holder come off that’s holding the motor
No experience with that one. But normally there is hole in the back of the motor. Behind that hole is a potentiometer with which you can adjust the motor speed. You can better leave the motor on the cassette frame and then dismantle the entire cassette frame from the boombox. Adjusting the speed is also easier, because you can still play a cassette with the cassette player removed from the boombox. Have fun
All went well , both were out together at one stage to get them to the same speed , plenty of swearing but great fun , onto the next