[julie_m]

I had a dimmer switch that was controlling a bedside lamp with a 40W tungsten filament lamp; but it blew up the triac when the light bulb failed. The replacement dimmer I bought doesn't like dimming a 40W lamp; it comes on suddenly at about 1/3 brightness and flickers alarmingly until turned up full.

The dead triac is a BT138, but the only triacs in my parts drawer were BT137s; which I believe have a less-sensitive gate and so probably would need a higher minimum load if they worked at all.

I think the point of these meters is a quick "sanity check", indicating whether or not it might be worth investigating a possible oddness on the mains supply with a better instrument.