I'm hoping for some quick pointers in determining the source of a fault with my overhead tile cutter. I'll be honest without taking it to bits I'm not entirely sure what type of motor (induction, synchronous or if it is actually DC other than input is standard 240V AC 50Hz. 

It works so long as I keep my finger on the on button. It is fitted with a KEDU KJD17 B which was assumed to be faulty so was switched for a brand new unit, and did not resolve the issue. Any pointers before I start dismantling and fault finding would be appreciated.

Thanks