If you’re testing old stereo equipment, a dim bulb tester can really come in handy. It’s not for testing bulbs, though, it’s a tester that uses a dim bulb to test other things. [Nicholas Morganti] ...

They’re consistently popular with the readers, which is admittedly part of my (and EDN’s) motivation to continue doing them. But I personally also find them fascinating; inevitably I come across at ...