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I changed several halogen spotlight bulbs and after less than one hour, one exploded. See image.

enter image description here

It's an Osram Decostar, 35W. Although the bulb doesn't carry a "CE" mark, the box did.

We regularly have bulbs dying, so I suspect something might be wrong with our wiring, but I don't expect the bulb to explode. Usually they just die quietly.

My real question though is the root cause. What could be wrong with the electrics?

I checked the dimmer switch wiring and it is correct (with switched-live in L1 connector). Is there anything else I can check for?

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    1) Touching a halogen bulb with your fingers can do that. 2) Halogen specialty bulbs often have a very short life because of crappy quality. So 3) It isn't likely the wiring.
    – fixer1234
    Commented Jan 24, 2018 at 11:26
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    Doesn't need to be velvet gloves; cotton or latex is fine :-) (or even using a tissue or paper towel between your hand and the bulb).
    – fixer1234
    Commented Jan 24, 2018 at 11:42
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    "One exploded after an hour" as indicated by @fixer1234 this is caused by finger oils or other contaminates on the lamp envelope itself (not the reflector). "We regularly have bulbs dying" is likely a socket problem, replace the bi-pin socket the lamp plugs into. When heat is generated by the lamp pins this type of bulb will prematurely fail. (I know as hot as the lamp gets while burning this is hard to reason, but when the bi-pins generate heat from poor connection the result is premature failure.)
    – Tyson
    Commented Jan 24, 2018 at 13:16
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    Thanks. I will likely replace the whole lot with LEDs anyway, but certainly want to avoid further explosions in the short term. If anyone wants to expand the grease issue into an answer, I'll accept it.
    – Tim
    Commented Jan 24, 2018 at 13:52
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    CE means nothing, it means the builder swears on a stack of bibles that they used non-leaded solder when they soldered it, and other trivial EU requirements, mostly environmental and not safety. Nobody checks this. There's no testing lab like UL, CSA or TUV. Look for those marks.
    – Harper - Reinstate Monica
    Commented Jan 24, 2018 at 18:09

2 Answers 2

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"One exploded after an hour" as indicated by @fixer1234 this is caused by finger oils or other contaminates on the lamp envelope itself (not the reflector). Its very important not to touch anything but the outer edge of the reflector.

Further what type of fixture is this bulb being used in? If the fixture is open faced situation such as this: enter image description here then the MR16CG must be used, (the CG stands for "Cover Glass") which has a self-contained lens. I mention this specifically because CG versions of the bulb tend to be harder to find and many people don't know when to use the CG version VS when the open face bulb is ok (i.e. enclosed fixtures).

"We regularly have bulbs dying" is likely a socket problem, replace the bi-pin socket the lamp plugs into. When heat is generated by the lamp pins this type of bulb will prematurely fail. (I know as hot as the lamp gets while burning this is hard to reason, but when the bi-pins generate heat from poor connection the result is premature failure.)

In the end, the best advice is to give is find an LED replacement that you are happy with. Unfortunately in many situations the MR16 halogen type of bulb is the hardest to replace with LED. It's very difficult to find LEDs that burn as brightly and with the colour clarity of the original - highly energy inefficient heat generating - halogen.

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    Many thanks. I've seen some 6W LEDs that claim to give 450lm/3000k. My current halogens are 430lm/2900k - so pretty close on paper.
    – Tim
    Commented Jan 24, 2018 at 14:56
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    Epic answer, your knowledge really shines through. Wish I could more than upvote.
    – Harper - Reinstate Monica
    Commented Jan 24, 2018 at 18:10
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    Shines through... I see what you did there.
    – JPhi1618
    Commented Jan 24, 2018 at 19:47
  • Spot-lightning is pretty much out of question for LEDs. As a rule of thumb: LED lamp comes with it's own socket. Drop-in replacements are merely a substitute. @Tim Check the light distribution angle as well because 430lm over 60° is "very dim", while over 10° is "very bright".
    – Agent_L
    Commented Jan 25, 2018 at 11:40
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Halogen lamps are very sensitive to oils because of there high operating tempature. Oils from fingers cause a hot spot on the envelope and this hot spot can melt causing the lamp to explode. I have seen reflector types also have early failures on high power projectors. when removing the lamp from the package use a tissue so you never touch the lamp (don't use tissues with softners or creams). If you do touch the lamp some rubbing alcohol on a tissue can clean it off just make sure it is dry before turning on. The life on some of these lamps is only 200 or so hours when run at the rated voltage. I was surprised by this when checking a fixture out for a friend. I added a dimmer that had a upper limit control to reduce peak voltage and that almost doubled his lamp life.

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