What's wrong with these LEDs?

[Peter Venkman]

So indecently relieved an order from Tayda and instead of sending me 4 red 3mm LEDs they sent me 41. The SKU number is A-661. I tried them out in my boards and none of them seem to work. I was using a 1/2 watt 2k2 resistor and nothing worked at all. I finally tracked down there problem to the LED and swapped it for some random 3mm clear/white ones I have know idea where that came from. What LEDs do you guys use? I've been wiring my switched to the foot switch PCB's from bitcheslovemyswotches and they worked great until I tried these LEDs. Am I missing something here? I tried testing them out on a bread board with different size resistors and born of them would light up. I'd like to stick to the 3mm size, color isn't important, but if I'm using the wrong size resistor for different colors please let me know what I should be I using for each color of you would be so kind.

[Ed Nice]

I use this: http://led.linear1.org/1led.wiz to avoid doing maths. You need to know the Vf and If which do differ from colour to colour and size to size.

The 3mm LEDs I have from bitsbox are 1.9Vf and 20mA, so for a 9v circuit, the [cheat] calulator says 390r.

If you get the resistance wrong, they'll either not light up or be really bright for a short period of time. Then pop.

HTH.

[Peter Venkman]

Thanks for the info but it turns out that after testing all of them, I just got a bunch of junk LEDs in the shipment.