Quote Originally Posted by DreadedHermie
Don't think it's static. Hot and humid here, all year long. (That's why I need the LEDs.) Dirty power's probably at least as likely, and I don't think that's it either. The problems occur when I hook up multiple LEDs. And they never seem to "blow" while they're operating.

When I got started, I deliberated toasted a whole grab bag of Radio Shack cheapies just so I'd get a feel for how it happens. This is strange. They seem to be working okay, and when I go to start 'em up again, nothing happens. On exam, they're cooked. I 4 x color-coded the wires so I'd be able to easily tell 'em apart--pretty certain I didn't reverse-bias 'em, too.

Maybe I "milliseconded" them by accident. In that case do they keep working but refuse to fire up next time?
Let's think about this.

If you apply input power to a constant current regulator with no load.
It will "see" almost no resistance at it's output.
Whatever your pre-set current is, the supply will raise it's voltage as high as it can to try to hit that preset.
So a supply with no load will sit at whatever voltage you have preset.
That means you must have a load connected when you turn on the supply.
If you power-up the supply and then try to connect or disconnect a load, the supply may get confused and voltage spike your load.
It's a very short spike, but more than enough to punch a hole in a led junction.
When testing I start with everything tightly connected, use variable voltage setting and bring it up slowly until I hit my target current. Then record the voltage reading.
I turn off the supply and wait a few seconds for the supply to drain before disconnecting anything.
Have not fried a big led yet.
Did eat a couple 3 Watt mpcb when I was learning, though.

Keep in mind, that it's before 11 am my time. So take anything I write before noon with a boxcar of salt.

Not a morning person.

Breakfast is up, I'll be back later.

Weeze