It's probably a little known fact but I've got a sideline going (like I don't have enough on!) fixing stuff.

A mate of mine brought me an ACME Samurai which wasn't lighting up. As suspected it turned out to be a fried LED (and driver board.. grrr) & trying to find a cheaper alternative than buying a replacement from ProLight drew a blank so... almost £100 later I fitted the new LED after giving the repaired driver PCB a darn good testing. Ahem. No light. My voltmeter measured 12V across the LED terminals. Oh no! The max. forward voltage of the LED is only 3.6V or so. Bums, so that's nearly a ton down the swannee.

Back to bits the assembly all went & I inspected the LED for signs of having been blowed up. Nope. Not a mark on it. All the little gold wires inside seemed intact too. So, onto my bench power supply it went. Still no output. Weird. Oh well, since it's pretty much a cert that it's broken let's try reversing the polarity (it always seems to work in films) - nowt to lose. ARGHH! MY EYES!!! It WORKS!

So back together with the blighter, noting that the red wire goes to the opposite side it would on the original LED.... and it's all fixed up now. Phew!

But what bugs me is that the original Samurai LED was made by a company called Luminus. It's a Phlatlight CST-90. The terminals are very clearly marked '+' and '-'. The replacement LED looked quite different and had no polarity markings. Before I even put the thing in the fixture I looked at every data sheet Luminus have for anything even resembling what ProLight sent me & in every case the positive terminal was the one on the right. Leave no room for doubt when the component costs that much, I always say. And yet...

So I've learned some valuable lessons with this repair.

Oh, and the reason the LED had failed in the first place? I think a distinct shortage of heat transfer compound between the LED & heatsink was the problem. Its days were numbered from the moment it left the factory. Funny, but the Equinox Promo Spot I fixed this week also had that issue. There was certainly SOME gunk on both surfaces but enough to transfer the massive amount of heat these LEDs produce in a small area? Nah.