Dissecting a Cree LED Incandecent Bulb Replacement

[MarkE]

Houston (or Austin), we have a problem.

A second Cree LED bulb has blown in the same fixture as before.  The fixture holds two bulbs.  The bulb that blew today has been installed in that fixture since the first incident of failure when I started this thread.

When the first LED failed I replaced it with an incandescent.  That bulb is still fine.

New info:  The fixture is in my "mud room" that incudes the clothes washer and dryer.  So there is a 240V outlet in use near by.  The new failure also occurred while I was using the 240V dryer unit.  BUT, the LED bulb went dark for a short time earlier when I stopped the dryer to check on the clothes inside.  It came back on a few seconds later once I restarted the dryer.

When the most recent failure occured I turned off the light fixture with the LED bulb after it did not re-ignite when power was cycled to the dryer (and the fixture) and let it sit idle for about 10 min.  After that it still did not ignite, so it was replaced by another incandescent.

The failed LED's glass dome has obvious residue on the inside now!  Definitely on one side, so I assume one of the multiple LEDs actually exploded.

So I am looking for advise (again).  Is there anything to be learned by dissecting the latest burnt out bulb?  What is the likely root cause of the LED bulb failures?  (I am thinking the fixture is probably on one leg of the 240V circuit in that area and inrush currents are f-ing up the silicon based elements in the LED's circuitry?)

Let me know what you guys think.  Especially if there is anyway to test besides "borrowing" a Power Analyzer from work.

I'd like to know that I don't have a potential fire hazard in the construction of this home's wiring.

M.

If you take the bulb apart, you will probably find that an electrolytic capacitor failed.  The problems with LED bulbs fall into:  Electronics vulnerability, and combined LED and electronics temperature limitations.  Whose bulbs are you using?  I would go with bulbs that have good heat sinks.

[mondrasek]

MarkE,

The bulbs are manufactured by Cree.  TK provided some great links to a tear down that showed the "innards" earlier in this thread.

I initially bought a "six pack" of these bulbs and, so far, none, have failed except for the two that were installed in the fixture described before.

Here is another piece of info I just thought of that might me relevant:  When I am in the area that is illuminated by the fixture that has the LED bulbs that I am inquiring about, I believe I have seen flickering of the light level.  The flickering always makes me look at the fixture, but the flickering does not repeat (immediately).  So I have dismissed that flickering thus far.  Hell, I have written it off (as it were) to my aging eyesight.

Thanks for giving this some thought.

M.

[mondrasek]

OH!  After walking around (blood flow) and thinking, I believe you might be on to something...

The fixture where the two LED bulbs have failed is a ceiling mounted unit that is completely surrounded by a glass dome "lens."  So it does not have good heat transfer capabilities by design AKAICT.

The other places that I have installed those similar LED bulbs are open air and therefore have convective cooling in their favor.  So the whole "heat" conjecture is a good possibility that I had not considered previously.  So thank you.

I am still concerned about the residue on the inside of the glass bulb however.  As far as I recall, the electronic circuit for these particular bulbs is isolated in the base of the unit and should not be able to reach the glass bulb.  So I can't see how a popped cap in that circuit could have created the debris on the inside of the bulb.  But it is something cool to check out on a tear down I think.

Let me know if you (or anyone else) has other ideas!

Thanks,

M.

[MarkE]

OH!  After walking around (blood flow) and thinking, I believe you might be on to something...

The fixture where the two LED bulbs have failed is a ceiling mounted unit that is completely surrounded by a glass dome "lens."  So it does not have good heat transfer capabilities by design AKAICT.

The other places that I have installed those similar LED bulbs are open air and therefore have convective cooling in their favor.  So the whole "heat" conjecture is a good possibility that I had not considered previously.  So thank you.

I am still concerned about the residue on the inside of the glass bulb however.  As far as I recall, the electronic circuit for these particular bulbs is isolated in the base of the unit and should not be able to reach the glass bulb.  So I can't see how a popped cap in that circuit could have created the debris on the inside of the bulb.  But it is something cool to check out on a tear down I think.

Let me know if you (or anyone else) has other ideas!

Thanks,

M.

Once the electrolytic capacitor fails the circuit cannot regulate.  Thre's lots of energy available to cook the LED.

[Pirate88179]

Since heat is the enemy to all high powered leds, I add a heat sink as seen in this photo.  It is made from an adult beverage can and works really well.  I have never experienced a failure of any of my Cree LED bulbs.  (Almost a year and counting)  Some of them, as you may know, I have gutted the driver board and use a high voltage JT circuit to drive them, and none of these have failed to date.

Now, if you want to talk cfls, I have had so many failures with them that I will never buy another.  3 of them actually caught fire while I was home...I mean...burst into flames and if I were not here, it could have been terrible.  I had to unscrew them while they were burning and toss them into the sink.  The ones that did not fail this way only lasted maybe 2-4 months.  The longest I have ever had a cfl last was possibly 8 months.

So, as you may be able to tell, I am a big fan of these Cree LED bulbs, both modified, and unmodified.  I am sorry you are having this problem with them and I suggest contacting Cree, and even offering to send them some of your failed bulbs for analysis.  I am sure that they really care about their products and, if this is some kind of design error, they must have had other complaints as well.  Have you checked your home wiring for spikes?  If you live near any large manufacturing companies, when they start up their equipment, there could be over voltages on your end or other damaging spikes possibly.

If your dryer is leaking moisture into the room, that could be a factor as well.  All of my cfl's that caught fire were in my bathroom, where there is high humidity after a shower.

Again, contact Cree and let us know their response.  This might help them improve their product so we can all get rid of those stupid cfl's!

Bill