Why does my halogen G9 bulb's wire break at the edge? - Page 1
Forum section: electronics / beginners

author: xchcui
author_rank: Newbie
timestamp: June 15, 2024, 12:21:19 pm
content: Hi.During the past 6 months,i replaced 3 Halogen G9 bulbs.Each one failed just after 1.5-2 months.They are rated as 40W/220V.Before that,i usually need to replace them after1.5-2 years.The interesting thing is that ALL the 3 bulb(which failed very fast)were not burned out at the coiled filament.The coiled filament remained intact,while the wire at the edge burned-out/disconnected(see attached photo-the wire between the foil and the coil filament).What may be the reason for that specific failure?Thanks.

author: soldar
author_rank: Super Contributor
timestamp: June 15, 2024, 02:16:57 pm
content: Same brand and batch?

author: xchcui
author_rank: Newbie
timestamp: June 15, 2024, 02:33:45 pm
content: Quote from: soldar on June 15, 2024, 02:16:57 pmYes,they were the same brand and i bought them the same day.I took into account that it could be a manufacturing defect(as you hinted in your question)but i am not sure.I am trying to understand why did the wire break precisely at that edge and not the coil,as it usually does?

author: themadhippy
author_rank: Super Contributor
timestamp: June 15, 2024, 02:50:44 pm
content: thermal expansion/contraction ,either of the glass or wire thats causing the 2 to rub together?

author: xchcui
author_rank: Newbie
timestamp: June 15, 2024, 04:27:45 pm
content: Quote from: themadhippy on June 15, 2024, 02:50:44 pmDo you mean that the wire may rub with the glass and break the wire?I assume that it is normal for a proper halogen glass and wire to expand/contract when heat/cool.Do you suggest that a bad design/defect halogen bulb construction may cause the glass to expand beyond the normal and rub/break the wire at that specific spot?

author: Gyro
author_rank: Super Contributor
timestamp: June 15, 2024, 08:06:26 pm
content: The halogen cycle works by re-depositing evaporated tungsten back onto the filament rather than the quartz envelope. The filament terminations run too cool for this process to take place so they thin over time. It used to be a problem with the amber lamps on (pre-LED) traffic signals, they weren't on for long enough to get up to proper operating temperature.

author: Gregg
author_rank: Super Contributor
timestamp: June 15, 2024, 08:09:05 pm
content: The bulb shown basically has two parallel open core and non supported inductors running at very high temperature. My guess is metal fatigue due to the filaments moving at mains frequency as well as thermal stresses at the sharp glass-filament juncture. A better design would be to make the thicker contact wires fuse to the filaments inside the chamber.

author: CaptDon
author_rank: Super Contributor
timestamp: June 16, 2024, 02:05:20 am
content: Were they Feit (I think that is the correct spelling)? That brand has had issues. I run a very similar design bulb in some special effects units for bands and I have had bad luck with certain brands. The first time I saw that 'dimple' in the quartz to support the filament I thought my bulb had melted!! My original bulbs had a free standing filament and lasted much longer. With the free standing filament I believe the support wires were much heavier. Mine were 200 watt 120 volt. We down scaled to 100 watt 120 volt with very little light loss but far reduced heat damage to the lenses as well as 1/2 the power consumption. Each of the effects units has two of these bulbs. Perhaps you can buy a different brand?

author: BILLPOD
author_rank: Frequent Contributor
timestamp: June 16, 2024, 12:47:40 pm
content: Imperceptible vibration is my guess. Set up a parallel bulb connected only by a thin wire.

author: xvr
author_rank: Frequent Contributor
timestamp: June 16, 2024, 12:55:18 pm
content: Older incandescent light bulbs have a special thinner right at this location in one of the power wires (as if the light bulb were an incandescent light bulb).It is used as a fuse to prevent a worn lamp from exploding if it is turned on when the AC mains voltage is at its maximum (but that doesn't always help).Maybe this halogen lamp has the same fuse, and your mains voltage is too high?

author: SeanB
author_rank: Super Contributor
timestamp: June 16, 2024, 01:17:05 pm
content: Just cheap junky lamps, run a little hot because they can save 1c over 100 lamps, from using less tungsten wire in them. The more reputable lamp manufacturers, like Osram, Tungsram and Phillips, despite being made now in China, at least do last longer. If you can find old stock made in the EU even better, I always had long life out of lamps made in Poland, France, Belgium and Germany, before those factories were closed, sold off and moved to China where labour was cheaper, and the quality dropped.If you can get the LED retrofits, if they will fit in the application as they will last longer, or change the socket to a different type of halogen capsule.

author: themadhippy
author_rank: Super Contributor
timestamp: June 16, 2024, 02:46:16 pm
content: QuoteAnother though,whats your supply voltage? If its 230v they aint gonna last as long,regardless of the make.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: June 16, 2024, 05:18:22 pm
content: Years ago, (back-in-the-day), fund raisers would sometimes sell light bulbs that were guaranteed to outlast common bulbs by a factor of 5, or more. Naturally they were quite a bit more expensive. Being the curious fellow I am, I ordered a few of these bulbs. The ones I got were marked 'Made In Poland', but then I saw the difference in the bulbs....they were labeled '130 Volt', and here in the USA, the voltage is 120 Volts. Upon further inspection I noticed the filament was thicker, which made sense. So, no fancy , technical breakthrough, just logical engineering.

author: amyk
author_rank: Super Contributor
timestamp: June 17, 2024, 02:33:37 am
content: Quote from: BILLPOD on June 16, 2024, 05:18:22 pmAnd lifespan of incandescent bulbs is inversely proportional tothe sixteenth powerof the voltage, so that 10V difference has a huge effect.

author: xchcui
author_rank: Newbie
timestamp: June 17, 2024, 10:49:16 am
content: I also thought that the voltage is the problem,but i had already checked the voltage and it is the same as the bulb specs,which is actually 230V and not 220V as i stated before.I didn't paid much attention to that,as i was pretty sure that the problem is the poor quality bulb and not the voltage,while my interest was why the wire breaks at the edge rather the coil.I was happy to buy the osram bulbs that were made in france/germany(which i used to buy few years ago and last long time),but you can't find them anymore and around my area you can find only 2 chinese brands of this bulb,which are not good.I guess i will keep searching for another brand of the halogen bulb.Thanks everyone for the help.

author: SeanB
author_rank: Super Contributor
timestamp: June 17, 2024, 12:05:12 pm
content: Yes I have light bulbs that date from the Phoebus Cartel era, and they will all last around 1000 hours, and then fail.https://en.wikipedia.org/wiki/Phoebus_cartel