Thanks to @angellonewolf I have the use of a megger
having taken the cover off I can see the melted wire that caused the smoke and fuse to blow. Before I bother to repair that- where would I stick the probes to check for insulation failure?
Measuring across the live and neutral supply leads gives me 103ohms - which seems ok?

having taken the cover off I can see the melted wire that caused the smoke and fuse to blow. Before I bother to repair that- where would I stick the probes to check for insulation failure?
Measuring across the live and neutral supply leads gives me 103ohms - which seems ok?