Quite possibly mentioned here elsewhere, way back in the early 80s, EA magazine featured a project that tests an electrolytic's ESR. My experience at the time i was coming across many failures directly caused by them especially in SMPS units. (Around the same time (although we didn't know it) the infamous bad seal issue for just about all cap manufacturers saw the 'juice' physically puked out of the cap resulting in terrible damage to nearby PCB tracks... i even saw glass body diodes dissolved internally by what was effectively an acid...
Enter a build project by Bob Parker in the EA magazine, a tool that would allow you to test the electrolytics often in-circuit on the board to reveal the device's Equivalent Series Resistance. The test unit was named "Genie" & i recall as young Tech Trainee virtually busting my savings to build the thing & finding just how great a gadget it was... Then the thing rolled out as a kitset (i bought two the day it came available at Dick Smiths & it continues to be available still)...
Here's a link for the original article:
http://www.your-book.co.uk/design/genie.htmThe tester has of course spawned 1000s of other devices by different makers but it amazes me that this one excellent idea by one very clever designer (whom i have massive respect for) has continued to live on, including a few improvements (see
https://www.altronics.com.au/p/k2574-esr-meter-kit/)
I have to ask, has there ever been any other diy-able project that became so well regarded?
Even the Mr Carlson features an EA logo unit in his latest youtube... (scoot to 42:22)