I sometimes ask myself, “Why do I bother with polarity reversal diodes? I use box headers. I check my cables. What could go wrong?”
Today I made a little modified bus board for my workbench. I tested it, looked good; the LEDs on it lit up as they should.
Tonight three VCOs were saved from oblivion by their polarity reversal diodes…
“How could the bus board be wrong? The LEDs wouldn’t light up if it were wrong! … Unless the LEDs were backwards too…”