Recommendations for stepper motor debug / repair

[magicniner]

not sure how many companies like MASSEY COGGINS LIMITED in liverpool that rewound motors are still in business these days

Plenty, Browill Rewinds in Sheffield are my supplier of choice, but I don't think they have the equipment to re-magnetise a stepper motor after you've stripped it and killed it ;-)

[m_c]

How big a machine is this?

Without seeing the machine, my guess is the wiring (or connector) to the motor has failed, resulting the in the driver going pop.
Easiest solution would be a suitable new driver, and replace any wiring between the driver and motor that flexes. It's unlikely the motor will of been damaged, but even if it has, a more modern square style motor shouldn't be that expensive.

However, without any photos or details about the existing control box, we can't really offer much advise.
To suggest replacements, we'd need to know what controller is being used, and the voltage the existing drives are using (along with a make/model number or a link to a datasheet so we can see what signals they need/provide).