Quote Originally Posted by DreadedHermie
Thanks for the continued support. The LED's may have won the first round (a Pyrrhic victory, for sure) but I am not giving up (yet). Taking the mutts for a walk to clear my head, and prolly reorder parts tonight.

Your analyses of the potential causes for the problems seem valid to me. All I know of operating this Mastech is the little pamphlet it shipped with. Doesn't cover much; includes a couple of recipes for LED disaster, apparently. I definitely was disconnecting the LEDs abruptly and this possibly resulted in some of my catastrophies, since the LEDs appeared to be working fine when I disconnected them. I think I was subconsciously (rather, consciously and ignorantly) trying to avoid a turn-off spike from the PS and in the process spiked them even more effectively.

Good analysis!

Disconnecting an alligator clip sounds "clean" until you see it on a 'scope.
Literally, thousands of "off n onnies" in a fraction of a second. Looks like a burst of rf.
If there's any inductance at all in the circuit, at these currents, the spikes will be higher than the dc level and will be in the wrong direction!
Once you get over a few amps, coiling a lead for strain relief is enough inductance to make trouble.
Then there are small, distributed capacitances...

Anything you can think of to help keep the next batch of LEDs alive will be appreciated.
So, next time, hard wire the leds and use the power switch on the supply to power down and we should be OK.
I've been running 13. 5 Watt leds from my Mastech for months with the supply on a timer.
Keep it set at 12.6V 3.4A.
So I bang the AC on and off with few problems.
(it did occasionally cause my UPS to "freak out" and beeeep at me.)

Had to plug the timer into a plain old socket and eschew the UPS for those leds because when it siezed-up like that it shut down the airpumps.
Not acceptable!

I feel your pain, brah.
Fried my first home-made geiger counter in the '60s.
Almost cried when the magic smoke got out.

Aloha,
Weezard.
Weezard Reviewed by Weezard on . Calling out to Weezard for LED advice My friend, I've read your stuff here and at Steve F.'s site. I want to build a dedicated flowering lamp using Ledengin 15 watters. (4 reds, 1 blue, and possibly 1 warm white; LM 317's so I can tweak the ratios.) Essentially, a copy of your 4+1 cake pan lamp but built on a 4 x 18" finned heatsink so I can see what's going on under it.) If I were to post my picks for power supply, resistor ratings / values, etc., would you critique and perhaps offer some guidance? I have already purchased Rating: 5