Blowing Bulbs

[chas]

I have a problem with the bulb in the light over my chart table which keeps on blowing. It is on the same circuit as the bunk lights which seem to last for ever! I don't know how the circuit is wired as it is all behind trim. I seem to have to replace said bulb about three times a season. As far as I can tell, it is not used markedly more than the bunk lights. It is in an open holder, so should not be overheating. If any electrical experts can tell me why it is happening, I woulod be very grateful.

Thanks

 

[halcyon]

Do you run the chart table light with the engine running, do you run bunk lights under engine.
Could be voltage, could be vibration, could be moisture.
Look for what is differant between the two uses or sites.

Few thoughts for this late hour.

Brian

 

[LadyInBed]

Could also be a loose connection somewhere.
You could replace the bulb with an LED as described in PBO.

 

[david_bagshaw]

Most likely to be voltage spikes from charging system

David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[chas]

Thanks - I probably use it marginally more while the engine is running but not much and other lights are used then which do not blow so much. It is mounted on a bendy stalk so vibration should not be a problem and it is dry.

 

[chas]

If it were a voltage spike, would'nt other bulbs and equipment be affected?

 

[david_bagshaw]

Yes, but the enclosure in the chart table light is smaller & perhaps the filiament is run harder to get the brilliance


Have wired 2 festoon bulbs in series to creat a night light in the main bathroom 4 years ago, they are on all the time someone is onboard, & still they work! last season 500 engine hours , 700 float charge by generator,perhaps another 2 weeks float charge connected to shore power, & 12 weeks on board,
Take alook at your nav light bulbs, bet they blacken after 15 hours.

David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[wishbone]

The most probable cause is movement or vibration, This occurs when filament lamps are hot! as lamps can handle a wide range of voltage, if you flick a lamp when on it sometimes go’s brighter before it blows, this is due to disturbance of the filament.

Wishbone

 

[snowleopard]

me too.

have a set of backup nav lights with 'festoon' bulbs. while the main lights with bayonet ends never fail, these blow with monotonous regularity.

you could try using an led instead (see latest pbo for details)

 

[anabel]

Does the bulb in your chart-table light have a close fitting shade? If so the problem may be lack of ventilation & the bulb is getting too hot. This would shorten its life considerably.

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[roger]

You can buy digital veltmeters cheaply nowadays. I bought some from LIDL at less than £5 each. A DVM would allow you to check voltages at the lamp fitting.
Its not difficult to make up bright LED lights.
For background illumination (say on a night pssage) the simplest is to buy a few 12volt LEDs and put 'em at low level around the boat.

<hr width=100% size=1>Roger

 

[Strathglass]

Probably the main reason the light is blowing is because it is on a bendy stalk.
You will be moving the light manually when the filament is hot. Nothing is worse for the life of a bulb.
It is unlikely that spikes are causing the problem otherwise your other bulbs on the same circuit would also suffer.
If you still consider that spikes may be the problem then the wires feeding the chart table light could be passed through a ferrite ring (both wires) and a 0.01 mf ceramic disc capacitor connected between each wire on the bulb side of the ferrite ring. The best place to do this would be just before the wires enter the flex tube. Doing this would minimize the effect of any spikes on the supply line to the bulb.

It may also be that the old bulbs on the same circuit are of a better quality than your replacement chart table bulbs.

Using LEDs as has been sugested would be the best cure.

Iain

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[Rowana]

Most likely cause is thermal stress, IMHO. If you are like a lot of us, you switch the light on to do your chartwork, then switch off again. Possibly doing this several times an hour, depending upon where you are in relation to shipping lanes, close to hazards, etc. I would suggest that part of the problem, as well as the other things described by others, is the number of on/off switching cycles of the lamp.

Jim

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[oldharry]

What type of bulb is fitted? Quartz Halogens being run at reduced voltage ( like throgh poor connections, undersize cable etc) have a much reduced life compared to their tungsten filament counterparts. Super bright LEDs seem to be a good alternative.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by oldharry on 01/04/2003 11:21 (server time).</FONT></P>

 

[oldsaltoz]

G,day Chas,

If the globe is a Quartz Halogen, it must be spotless when fitted, no fingerprints at all, handle with a tissue when fitting. Any rubbish on the lens will generate heat.

If not, the chart light will be a much higher wattage than cabin lights (More light), if you reduce the wattage you will loose some light, but it will last a little longer in this environment.

Hope this helps

Avagoodweekend. Old Salt Oz /forums/images/icons/cool.gif

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