LED blew out question

[ReefPharmer]

I have a DIY set up I bought from another guy. Its your basic set up with a heatsink, running 2 strings of 12 white and 12 royal blue cree. One of the royal blue bulbs burned out (it does not light). However all other bulbs are on and light, including the bulbs "downstream" from that led. I thought that if the bulb burns out, the bulbs down the stream stop working since the string is broken?

The strings are not parallel and each string has its own meanwell driver.

Any ideas? (i ran the continuity test on the bulb and it doesnt light up with the multimeter.)

[andbob25]

I am having the same problem with a couple of my Cree less I think I may have had water splash onto the emmiter is there any way that could have happened to yours

[ReefPharmer]

No i dont think so, they have optics and a cover between the lights and water

[ronsonol]

Leds downstream don't turn off since they are still gettting power through the blown led.
The exact same thing can happen when one led is wired backwards, all light but the one that is wired wrong. If your other leds light with a multimeter, than assume its gone.
All the leds won't go out unless the break is in the wire ... then they should all be out.
Since its a meanwell, adjust the current down to the desired setting to compensate for the lack of the led until you can replace it.

[ReefPharmer]

i wired in 1 amp fuzes into the curcuit so that if things go haywire, the fuze blows

[kcress]

The out led has failed shorted.

[jkopp36]

The out led has failed shorted.

I assume they can fail open too?

[TheFishMan65]

Yes and then none of the string will light.

I have to go investigate one of these tonight. Any thoughts for causes other than water splash?

[Chris27]

Yes and then none of the string will light.

I have to go investigate one of these tonight. Any thoughts for causes other than water splash?

Dust, improper soldering, improper connection to the heatsink, faulty LED, etc...

Sometimes electronic components just go for no good reason....just the way it is. The common mistakes can be weeded out with a good visual inspection and a few checks with a multimeter.

[TheFishMan65]

Thanks for the list. Just want to make sure I cover all the bases (I already planned on checking most of those)
Sometimes electronic components just go for no good reason.
Yes, but I thought faulty electronics usually went pretty quick (first 3 months or so). One of the reasons that extended warranties for electronics are not a great buy. This one has been up since November (8 months).

[nuclearheli]

I assume they can fail open too?

Funny thing about short's and open LED's. The definition below say's it all.

A short circuit (sometimes abbreviated to short or s/c) in an electrical circuit allows a current to travel along a path where essentially no (or a very low) electrical impedance is encountered. The electrical opposite of a short circuit is an "open circuit", which is an infinite resistance between two nodes. It is common to misuse "short circuit" to describe any electrical malfunction, regardless of the actual problem.

That being said I admit, I am "common" because I commonly misuse the term short to describe both a short circuit and an open circuit. It's like a song in your head you just cannot get out.

LED's can short out - other LED's in the series will remain lit.
LED's can fail open - no LED's light up. Circuit is broken

[kcress]

Modern semiconductors simply don't fail out-of-the-box. If a LED fails it's because it was run out of specification. It could've been a brief instant or a long simmering assault. It could be both. An example would be a bad commissioning that over-currents the LED for just a moment. That's enough to change the LED's dynamic resistance. That will always be a bad change.. The internal die will run much hotter leading to a premature failure.