Usually it is fairly simple to use the TM motor controller manually, if controlled by a analogue input it just requires a 5k pot.
If, as in some later versions, the input signal was 20Hz PWM and requires a suitable circuit, some have built them from a 555 circuit.
I have done it with a 8 pin Picmicro 12f series.
Post a pic of the motor board or any part numbers.
If the board is shot, then you either need to repair it or use one of the after market made by KB drives etc.
Max.