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G6Tanuki · 5th Feb 2019, 7:44 pm

What's the supply/earthing scheme involved? (I'm only really familiar with "TT" since that's what I've had in my houses/outbuildings for the last 30-odd years).

If the problem was shorted turns somewhere within the transformer I would expect it to blow the unit's fuse or the plug-fuse (or at least get very hot and smelly!).

My initial opinion is that the issue is a primary-side live-to-ground fault-current - either in the transformer (insulation breakdown/primary-to-ground short) or because a primary-side suppression-capacitor/mains-filter to ground is failing. Even shorting neutral to ground will cause a trip on a "TT" scheme.

5th Feb 2019, 7:44 pm	#5
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,997	Re: KW 108 monitor scope woes What's the supply/earthing scheme involved? (I'm only really familiar with "TT" since that's what I've had in my houses/outbuildings for the last 30-odd years). If the problem was shorted turns somewhere within the transformer I would expect it to blow the unit's fuse or the plug-fuse (or at least get very hot and smelly!). My initial opinion is that the issue is a primary-side live-to-ground fault-current - either in the transformer (insulation breakdown/primary-to-ground short) or because a primary-side suppression-capacitor/mains-filter to ground is failing. Even shorting neutral to ground will cause a trip on a "TT" scheme.