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burning in and electric lights

P

philsparks

pfm Member
Recently experienced something that made me muse on the whole burning in discussion.

As an ex electrical engineer I normally hold with the if mantra that if you can't measure it - it's probably imagined. However my Teddy Dac did gradually get better (and I mean REALLY better, noticably better) over a couple of weeks or more.

We had a loft conversion done about 2 years ago and there are 12 little halogen downlighters up there (the little GU10 things).

For the first few months we had bulbs blowing every week or 2. I'm sure I replaced all of the bulbs, and some of them more than once. It was so annoying that I almost got the electrician back to have a look at the circuit.

However , in the following few months the rate of blowing went down. A year later and t's down even more - I guess I've probably only replaced 1 or 2 bulbs in the past year. What's going on?

It could be that by a process of elimination, I've now got a more robust set of bulbs, and weeded out the weaker ones (evolution for lightbulbs?!). However if that was the case - then whenever a bulb did blow, I'd expect to have to replace it once or twice until I found a good one - that's not happening.

I could be that something else has happened - perhaps my electricity voltage has gone down? But if that's the case I'd expect the rate of bulbs blowing elsewhere in the house to have changed - it hasn't.

Given that the loft is a long way from the consumer unit, and the circuit is simple twin and earth wire and a switch I wonder if there is some sort of 'burning in' going on here. I'm sure the circuit wouldn't measure any different, but it is a little 'odd'.

Friday night musings
Phil
 
Assuming that this isn't a wind up have you measured the voltage?

We are quite high here at 252v measured on my trusty Avo and my GU10s last 5-6 years before going to that great spark in the sky. Some are still the original at 9 years. These are used in all of our bathrooms so are always being switched on and off.

What make are you using?

Cheers,

DV
 
Interesting observation. I wouldn't need convincing about new kit 'burning in' to good sonic advantage, but domestic ring mains cable? Fairly low amperage cable too, I'd guess.

However, despite being a total layman, I can see a correlation. My dedicated 10mm2 cables and RCBO/hard-wiring installation steadily improved the presentation/dynamics of my system when it went in a few years back, and in my blissful ignorance I put it down to the molecules 'aligning' themselves with the constant flow of electricity (and possibly lowering impedance?). Friends with similar installations have found the same, but even my physics lecturer friend feels that my theory is a bit far-fetched !:)

However, halogen lights are not hifi, and I know nothing about them, but is it beyond the realms of possibility that they're very sensitive to fluctuations caused by the 'burning in' process? Certainly, i.m.e., 'burning in' of hifi is not a smooth process; more a 'two steps forward, one step back' situation.

All heresy to electricians and sane people, of course (and even manufacturers?), but interesting nonetheless.
 
If all these bulbs are run from a modern 'electronic transformer' aka a crude 5khz SMPS designed to run halogen lighting I'd put money on its output voltage dropping a tad as the main input-side reservoir cap ages.. That's all.

Incandecent bulb life varies very roughly as v^4; tiny changes make an enormous difference. These cheap SMPS are really dumb and poorly-regulated; likely rather worse than the equiv dumb 50Hz 600W transformer in fact (but no flicker)


Edit to add - don;t worry, it is just the classic 'bath tub curve'. We/our engs see the same thing in new buildings generally - a flurry of failures at first, then nothing for years, then failures increase again as natural end-of-life is reached.
 
It's not a wind up - honest, although, looking back I can see that it could easily be a somewhat-later-on-a-Friday-night-after-a-few-more-beers-kinda-post.

- GU10s are 240V, so no transformer as far as I'm aware - just a bit of wire and a switch
- it could have been a less than decent batch of bulbs (can't remember the make), but the first few were replaced with any old bulbs from the local B&Q, and still there were quite a few failures, but the rate of failure still declined after a year or so.

Can't remotely explain it, but I do think it's a bit odd. It's just like the 'burn in on the hifi' - I can understand how the LP12 sounds better after half an hour as it gets warmer, but cannot understand how a box of resistors and capacitors sounds better after a week - it just does!

Phil
 
I find GU10s are terribly unreliable and quality varies greatly. I've had some that blow the light circuit when they go whereas others don't, something inside I am led to believe.
 
Can you remember whether there was a tendency to blow at a particular point in the usage cycle? I mean did they blow more often when switching on or off, or was it just random? The reason I ask is that when a circuit is cut, as I'm sure you know, the magnetic field around the cables collapses and that energy can cause a very high frequency spike. As the switches tarnish over time, they may produce a different frequency and amplitude of spike due to the way and rate at which contact is effected between the two surfaces. You could test this by replacing the switches with brand new ones and see if bulbs start blowing more frequently. If this turned out to be the reason, then inserting a small capacitor tuned to the circuit could save plenty of money in light bulbs. Perhaps the tarnished switches, or tarnish elsewhere in the circuit acts like a small capacitor and smooths the spike.
 
Worth checking your mains voltage carefully, i've had a high of 273 and a low of 215 this week.
Dodgy split phase transformer i suspect.
 
I find the GU10s blow quite frequently in the bathroom if I have been moving things about in the roof void directly above them. Like tungstens they too don't like movement or vibration.
 
sonddek said:
Can you remember whether there was a tendency to blow at a particular point in the usage cycle? I mean did they blow more often when switching on or off, or was it just random? The reason I ask is that when a circuit is cut, as I'm sure you know, the magnetic field around the cables collapses and that energy can cause a very high frequency spike. As the switches tarnish over time, they may produce a different frequency and amplitude of spike due to the way and rate at which contact is effected between the two surfaces. You could test this by replacing the switches with brand new ones and see if bulbs start blowing more frequently. If this turned out to be the reason, then inserting a small capacitor tuned to the circuit could save plenty of money in light bulbs. Perhaps the tarnished switches, or tarnish elsewhere in the circuit acts like a small capacitor and smooths the spike.
Click to expand...

always when switching on
 
Philsparks is certainly not imagining it, but Bob has the correct answer as far as Im concerned.
My office has some 30 of the things controlled by 5 seperate dimmer circuits. They ALL failed within 4 weeks.
I had been warned that this would happen by the guy that makes the light control panel, saying just how variable the quality of bulbs is, and that invariably the ones supplied with fittings will be the cheapest available. He even advised (correctly) that I should be wary of even fitting the supplied units, and just get some proper branded ones from the off. Would have saved me a lot of faffing up and down step ladders for certain.
Philips, crompton and Sylvania seem to work well for me, especially the ones that offer higher equivalent light output - ie a 35w has equivalent output of 50w etc.
Non of the bulbs are exposed to sudden on / off hits - they all have a minimum fade up / down of 15 seconds to help them through thermal shock - looks good too :)
 
Pete the Feet said:
I find the GU10s blow quite frequently in the bathroom if I have been moving things about in the roof void directly above them. Like tungstens they too don't like movement or vibration.
Click to expand...
Particularly when they are on. Quite robust when cold, not so when hot.
 
Bob McC said:
I find GU10s are terribly unreliable and quality varies greatly
Click to expand...

The "redder" they look, the longer they will last. This means, almost without exception, that the 20 or 35W jobbies will significantly outlast the 50W ones.
 
Phil,

I also saw exactly the same issue in our kitchen - all 7 GU10's blew over a period of a month or so. No problems with Sylvania or Philips models since.
I am also more inclined to think that they were a cheap dodgy batch first time around rather than burn-in.
 
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