Hi Frank,

as always – the easiest way is usually the best way! So simple but very effective.

That remembers me to a similar way to test the very first time an unknown table radio with tubes lineup. If a shortcut (power transformer, electrolythic capacitors etc.) occures the lamp (e.g. 75 W, 230 V) shows it by glowing bright. A “breathing” is the actual formation process of  an electrolythic capacitor in the power supply – and dark light means “o.k.”. It is always good to keep such bulbs for testing reasons…

Your Automatic Fuse is another good way – I was looking since years for such a simple circuit for my double meter Lectron block (V + mA) to secure the expensive instruments (and other Lectron components, of course).