[The Philpott]

I must admit i generally leave o/c bobbins in place, snip one end out of circuit just in case, and replace with a component resistor. Once or twice, having removed a bobbin i regretted it due to flakes of dust and shellac being released to float around inside, unerringly settling on the glass or scale plate.. (This was on avos, not insulation testers)

Dave