With more and more stuff running on 3 V, I decided to make a quickie adapter for the very nice SparkFun 5V-from-an-AA supply that lives on my bench. Then I’d have which ever voltage I needed right at hand.
Just a 3.3V reg with 0.1″ male and female connections – simple as could be. Until I tested it and found I’d wired the input of the regulator to the female side.
At least I found it before I potted the wiring on the bottom in epoxy…
A little later: The regulator is replaced and it all works fine. There will be no need to discuss what the alcohol I used to clean the flux from the repeated solderings on the bottom did to the pretty labelling, or the jelly-side-down incident with the potting epoxy.