We have a pair of display cabinets which each have 2 spotlights in. They have small bulbs with a small screw thread and were quite hard to find - at least not in the usual places - when one went a couple of weeks ago - the first to go for ages.
The ones I ended up buying were a different wattage (25w v. 30w) so I bought 6, so I could replace them all, with two spare - thinking that'd be enough to last me out.
One went within a week and it's replacement only lasted a couple of days.
Is there something I should be looking at in the fitting or is that just bad luck/cheap bulbs (though they weren't, especially!), as I'm now down to 4 and the store had no more - and I don't really want to stick another one in just for it to blow, if there's some preventative action I can take first.
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Filaments blow by burning through.
When cold the resistance in the filament is very low so a big current passes when switched on (heating the filament, which increases the resistance, and reduces the ampage being drawn once at a steady state). If there is a particularly narrow point in the filament, this will be the point of greatest heating.
Over time the tungsten sublimates from the filament, and ends up on the inside of the glass causing a gradual narrowing of the filament, and hence failure, usually at the point of greatest current flow, ie when turned on from cold.
When bulbs die early in life I would expect it was a crap bulb: imperfect filament, trace of oxygen in the bulb (or a small leak allowing it in)
LED bulbs usually fail when the circuitry cooks - the LEDs themselves should last decades
Last edited by: Lygonos on Tue 1 Jan 19 at 19:01
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Heat & Over voltage
Most bulbs you buy are designed for 220v. The average voltage in the UK is 243V (its declared as 230)
Heat, very badly designed and poorly made holder/enclosures exist in abundance, poorly made bulbs with little heat transference to holder ditto
Crap bulbs in short.
Last edited by: Zero on Tue 1 Jan 19 at 19:25
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>>LED bulbs usually fail when the circuitry cooks - the LEDs themselves should last decades
>>
I was dumping a box full of "free bulbs " at the tip recently.
As they were the florescent type I of course went to the appropriate cabinet that had mostly
the familiar long tubes in but also an awful lot of LEDs.
So much for long life :-(
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>>Crap bulbs in short.
I have had several fail in the last few weeks.
60W clear candle BC which IIRC and not supposed to be on sale?
The fitting was cap up. The failure was a bang that tripped the RCD and SWMBO was not amused.
I found the glass envelope, intact on the floor and the cap still in situ.
The last time it happened I fitted a branded Halogen version that I had in stock and that lasted a week.
New years resolution.
Bin all the cheap bulbs - I am off to get some LEDs :-)
I do hope they last.
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We were always replacing misc. bulbs in our old house (new build 2008). They were mostly filament GU10 types in all rooms. Lamp bulbs blew quite regularly as well. Blown GU10s were replaced by LEDs which never blew during our tenure. I suspected that there was a supply or wiring issue. Most of the lights here are pendant types. All bulbs have been replaced with LED bulbs, but none of the lamp bulbs have blown (although some of them are LED).
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Thanks folks... I actually had LEDs in these lights from some some back, when they were really quite expensive. SWMBO wanted the old warm colour bulb back in for the withering so that's why I changed them back.
I'll have a browse through the 2000+ page catalogue which CPC sent me just before Christmas for some new ones I think. Or maybe search online, which would be easier!!
btw the recent purchase bulbs were Homebase brand, but I suspect end of line as few stores had them. They were really very cheap too, compared to the few other places I could find them.
Last edited by: smokie on Tue 1 Jan 19 at 23:34
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You Mazda lamps!
I can remember this TV ad from the 50's
www.youtube.com/watch?v=yKDH-cuH3nE
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What causes bulbs to blow? - Lygonos
