Exploding Light Bulbs

The elderly couple whose house I look after have recently reported that three light bulbs have "exploded" when turned on, and dropped the 6A circuit mcb each time.
They didn't mean that glass was everywhere, but they obviously went with a real bang. This is a 5-branch ceiling fitting, with 40W clear golf-ball incandescent lamps in close-fitting open ended glass shades, cap up at about 45 degrees. The problem has only started since I started using Supalite branded bulbs instead of Tesco branded ones.
Here's the latest failed lamp, with a hole blown in the cap:
http://www.mainbeam.f2s.com/supalite.jpg
I'm concerned because of possible damage to the fitting, and because one of the elderly couple will stumble around in the dark sooner than reset the trip or ask for immediate help. I really, really don't want to go through choosing a new fitting with them, so what should I do?
Carry on and work through the remaining stock of 10 Supalite bulbs, in the hope that the rest will die more quietly?
Throw the Supalites away (the ebay seller is now NARU, though several other sellers still sell this brand) and buy a better brand? If so, which brand?
Report these lamps to Trading Standards as potentially dangerous?
Find an alternative technology lamp that will replace 45mm globe lamps? Which? The overall room light level must not drop - they both have incipient cataracts and other visual problems.
--
Kevin Poole


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It's not unusual for certain types of lamps to fail in this way. The support mechanics for the filament collapse and short circuit. There is usually an internal fuse - but that often can't blow quick enough to prevent an RCD tripping.
All you can do is try a different make. As regards trading standards it's no more of a safety hazard than a single bulb failing and plunging the room into darkness. It's up to the individual to provide a backup system in this event if it is so important.
Or you could try CFLs. They don't normally trip a breaker when they fail. LED types often do.
--
*Did you ever notice when you blow in a dog's face he gets mad at you? *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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I've had a couple go bang, with a lot of magic smoke <http://www.admac.myzen.co.uk/bulb/
--
Alan
news2009 admac myzen co uk
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Alan wrote:

Wonder what C3 and C8 are for?
--
Tim Watts

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RF Suppression? Get it tested and then "forget" to fit them as they don't effect performance?? Cynical? Yes...........
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Bill

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Bill wrote:

:-)
to be fair Ive seen a lot of that in my time..stuff the designer put in so 100 out of 100 radios worked, not just 85%..but then they took em out and decided 15% reject was cheaper than the extra components.
Or sold em anyway and hoped they didn't get too warm...
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Bill wrote:

They do look wide enough to be taking some sort of plastic moderately high value capacitor that might be good for noise suppression.
Yes, I think you're ever so cynical *cough* ;->
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Maybe required in some regulatory regions and not others, or required for some supply voltages or power outputs and not others. Enables a scale of mass production beyond just a single product.
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Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
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On 04/12/2011 10:29, Dave Plowman (News) wrote:

The two end supports and the two intermediate filament supports are intact. All three spans of the filament are broken, and the majority of one of them has disappeared.

Even when it blows a hole in the cap? I haven't looked inside the lampholder, as I don't want to worry the occupier unnecessarily. She only goes out of the house when I take her.

Well, yes: it's a bungalow, and the lights are on two circuits, and there are battery-powered lights in the hall and bathroom which we've advised them to leave on during hours of darkness, but some old people can be stubborn.

Not easy to find within the same overall dimensions as incandescents. See also my reply to fred.
--
Kevin Poole


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They look very similar to the CFL golf ball bulbs that I have frequently bought from IKEA. There are other suppliers but the IKEA ones a re a good price and seem to last.
Jonathan
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If the lamps are blowing frequently. you could increase their life dramatically by fitting a diode in series with the switch. Will reduce the light output and the efficency, though.
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*If you don't like the news, go out and make some.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On 04/12/2011 19:05, Dave Plowman (News) wrote:

Seasonal message: That's what I do with mains powered xmas light strings; I put a diode in the plug in series. I have strings approaching their 20th year!
--

Graham.

%Profound_observation%
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On 04/12/2011 19:18, Graham. wrote:

Our 60 yr old Snow White lights had 12x20v bulbs, but eventually they had to be replaced so I ended up with 10x37v bulbs that show a really nice warm glow and will probably last forever. Pete
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Somewhere in the loft, I too have a set from the same era. I've got a feeling they might also be the 'Snow White' brand. In the end, I ran out of spare bulbs. To keep the set working, I used to put some silver paper in the sockets of the dead bulbs (to short the contacts out), screw the dead bulb back in, and run them from a variac at reduced voltage. When several bulbs had gone, I too changed to using a series diode. Surprisingly, you could see the 25Hz flicker.
--
Ian

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Ian Jackson wrote:

Just trying to get my head round how a diode is only letting through every fourth half cycle?
Surely the normal lamp has 100 Hz flicker, which the diode halves?
Chris
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Chris J Dixon Nottingham UK
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You're right (of course!). 'Twould indeed be 50Hz. But I recall that you could just see the flicker when you weren't looking directly at the lights.
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Ian

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Ian Jackson wrote:

That is because peripheral vision is more sensitive to flicker.
http://en.wikipedia.org/wiki/Flicker_fusion_threshold
Chris
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Chris J Dixon Nottingham UK
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Indeed. At one time, I used to be very aware of it when (not quite) watching TV pictures (on CRTs, of course). In the USA, where the field/frame rate is 60/30Hz(ish), I found it totally absent. In latter years, I seemed to notice it less (or maybe, eventually, simply got used to it).
--
Ian

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On 07/12/2011 09:52, Ian Jackson wrote:

Modern LCD TVs are often generating 100Hz or higher interframe rates and their intrinsic flicker even at 50Hz is usually less than a tube based display. Large plasma ones at basic rate are more annoying in peripheral vision.
A wall full of large screen TVs can be a bit disconcerting in shops. YMMV
Regards, Martin Brown
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It will depend on the lamp design, but the persistence of the filament usually prevents any noticeable flicker even with a diode.
--
*A person who smiles in the face of adversity probably has a scapegoat *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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