I am working on restoring/repairing a Macintosh SE/30 machine, and I'm at the point now where I'm debugging why SCSI isn't working on it anymore. I found some schematics for it online, as well as some troubleshooting guides. The project ahead of me was to 'buzz out' all 44 pins of the SCSI interface chip to points elsewhere on the board, to figure out why it's failing. I knew I'd need a good continuity tester for this. I have this feature in my multimeter, but I didn't want to hear that annoying beeper... I wanted a visual response instead.
I had toyed with the idea of using an LED Glow Stick flashlight, like I used for my "Sonic Screwdriver", just add in two wires going to test points. I swung by the auto parts store, and instead saw this there for $10:
Knowing now how easy it was to make the "probe" here, and how well it works, I think I might go back to my original idea of using an LED Glow Stick flashlight, and just tapping into the circuit to add in two probe wires, terminating in these pin probes. In retrospect, I already had everything I needed before I bought this thing. Heh!