John jumps to a conclusion although he may actually be correct...
Your VAX will not have stopped for "no reason" - there will be a reason.
The power cord may have been continually strained during use and a wire either become disconnected or even snapped inside the cable. Examine the whole cable between your fingers (unplugged of course) for any signs of weakness or unusual damage. If you can inspect the plug and the wire terminations inside the machine then do so.
There may well be an overheat cut out which is why John suggested waiting 30 mins before trying again - the socket you use may be defective - the on/off control switch may be defective - an internal wire may have failed (most unusual) the motor brushes might have disintegrated (you would have heard or even smelt this) and the motor windings themselves may have burnt out.
John's burnt out motor is an expensive diagnosis - it is often best to hope for the cheaper type of fault.
Good luck...
Peccavi
July 2009