Turns out that when I blew the cheap chinese controller I took out the Bob too, so when I installed the new driver strange things went on including motor running slow , pulsing on and off . When I checked volts at the relay and pot terminals the motor started and the circuit breaker in the machine blew. Alsofound that the the Bob relay was continually made . Replaced BoB and tried again and this time the controller does not work at all . I dont know whether it is duff or whether I have blown that too. They are unisolated units with a floating pot input like lenze so not suitable to connect the pwm direct from the computer . I hadnt been bothered as I hoped to use the DIYCNC board to overcome that but now when ordering a replacement and after some consideration I have decided to go for this .
https://inverterdrive.com/group/DC-T...0-Isolated-1Q/

A bit more pricey but will take the computer pwm output
Arriving tomorrow so will have another go then.