I just finished a couple of Cigar Box amps. Everything went well until I soldered the LED leads. I bought 2 prewired kits from Gitty. I checked the the leads with an ohm meter and had good continuity from the circuit board to the ends of the lead. Neither one of the LED's lit up when I turned on the switch. The amps both work well although not to loud. I can't figure out why the LED's don't lite. Take a look at the picks. Any help would be great
you had it right: depending on the the LED type, it will operate at a voltage drop of anywhere from 1.7v for dim red LEDs to 4.5v for bright white LEDs (check your spec sheet) and you need the resistor to drop the rest of the voltage (wired in series) or else you get a wonderful one-shot flashbulb-LED and then all the magic smoke will leak out.
A lot of LED's have a flat spot next to one leg. That's the Cathode. I could never remember what that meant until somebody pointed out that Cat's are negative... So Flat spot to ground.
Just as an added note, though they are cheap you can salvage LEDs out of old junk appliances and save some change.