Blowing GU10's



This is what is hard for people to understand, TNP, even though they experience just that every day in their own lives.
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On 2013-05-16, The Natural Philosopher wrote:

That's a lot more substantial than a 50% decrease in life.

Ha, you got me there. But seriously, I was hoping for some explanation involving the dissipation of the extra 10% of heat generated.
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On 16/05/2013 13:59, Adam Funk wrote:

I _think_ the bulb life is limited by the filament evaporating. Take the temp up a little, and it evaporates much faster - it's an exponential relationship.
Andy
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It's a very fine relationship between efficiency and life. Drop the efficiency and the life goes up dramatically. Think of, say, panel illumination lights on a car versus headlamps - the headlamps are likely to fail three or more times as often.
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On 16/05/2013 14:37, Andy Champ wrote:

The formula quoted in the wiki (don't know its source) is:
new life / old life = ( old voltage / new voltage ) ^1^3
(that raised to the thriteenth power in case it does not look ring in ASCII)
so 1000 hours at 230 volt would become:
nl / 1000 = (230/240)^1^3 = 0.58
so life = 1000 x 0.58 or 580 hours at 240V.
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On 16/05/2013 18:08, John Rumm wrote:

They aren't lasting that long. It's a matter of weeks.
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Dave - The Medway Handyman www.medwayhandyman.co.uk

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On 2013-05-16, John Rumm wrote:

Far out: you don't run into 13th powers very often.
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snipped-for-privacy@nospam.invalid says...

Changing the subject slightly.
I wonder if people understanding of bathtub curves has altered, now that baths come in so many strange shapes?
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Sam

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On 16/05/2013 18:47, Sam Plusnet wrote:

The cross section is basically the same regardless... ;-)
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On 16/05/2013 20:43, John Rumm wrote:

Lengthways or sideways :)
I always use the length. Give you the chance to have a different slope at the two ends.
Andy
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wrote:

Fnarr fnarr.
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snipped-for-privacy@nowhere.null says...

Not true. Our "new" bath is vertical at the tap end (fair enough) but is d@mn near vertical at t'other end as well. It wouldn't do to illustrate a bathtub curve at all.
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On 18/05/2013 22:28, Sam Plusnet wrote:

I was referring to across the bath's width rather than length... but either way, the only real requirement for a bathtub curve is one that falls, stays levelish for a bit and then rises again.
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snipped-for-privacy@nowhere.null says...

If you modify that to... Falls very steeply at the start, stays at a fairly constant low level and then gradually rises - I would agree, but it's that initial plummet & the gradual rise at the end that is characteristic.
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On 20/05/2013 19:27, Sam Plusnet wrote:

Sharp fall at the front sure... the end rise will vary depending on the typical causes of failure. Some designs hit a wall at end of life due to particular component limitations etc, so it can be as steep there aswell.
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On 16/05/13 13:59, Adam Funk wrote:

when clearly that cant be the failure mode? I'd look at oxidation at or around the operating temperature. I bet that's a sharp knee.
Or whether in fact the material strength starts to undergo a transition at that temperature
To get light efficiency you run filaments as hot as they can go.
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On 2013-05-16, The Natural Philosopher wrote:

That's rather like what I meant by heat input & dissipation. I guess in your example, a 10% increase in heat generation is enough to push the temperature over the edge.

Right.
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On 14/05/13 20:02, The Medway Handyman wrote:

that's about how long they do in fact last IME
10 weeks on average.
install LV and get around 3-7 years.
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Why you fiddling about with incandescents? Get LED ones.
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Tim

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On 14/05/2013 20:02, The Medway Handyman wrote:

Others have already mentioned voltage, and vibration. Lamp brand also has an effect. I found a batch bought from TLC outperformed some others that I had tried previously for example.
There have been various discussions on this in the past (a particularly good one some years back that got hijacked by one of our US based trolls).
One thing that a number seem to agree on (myself included) is that mains voltage halogens are also intolerant of noisy switching, So it is worthwhile swapping the switch for a new one as a precaution. (or better still using a soft start dimmer to drive them)

For a real fix however, swap them for LV halogen or LED
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