The local church that I attend have asked me to try and find a bulb supplier in the UK preferably, who can supply some 120V 7.5W (7 point 5 W) Screw-In bulbs which are used to illuminate the foot pedal keys on the Allen organ.
I have looked at that many websites, I feel that I am going dizzy.
Could anyone possibly help with some information lease ?
With kindest regards,
James
What size screw base?
Could try the UK distributor? Chances are they will know where to source in the UK if available?
PS some other options when you have established what ES fixing it is:
Does the church have a maintenance contract for the organ? If so, you should be able to get failed bulbs replaced under that.
Otherwise, have you contacted the Allen Organ people?
Failing that, you may be able to re-wire the lights to connect to the incoming mains rather than to the 120v transformer, and then use 240v bulbs.
[Since the organs are made in the USA, everything is designed round 110/120v, and they use a step-down transformer for Europe. The church I used to attend has one - which I was instrumental (sorry!) in acquiring for them, and the transformer causes fun and games at PAT testing time because it's connected straight across the mains even when the main switch on the console is off!]
Might be better to run low v to the holders instead, and make up LED clusters. You get 50,000 hour lights that way.
NT
I see you haven't got much help yet.
What's the diameter of the thread on the bulbs concerned? 7.5w suggests candelabra base (12mm) lamps, often used to illuminate the translucent base of table lamps in the US. Give us an idea of the overall shape and dimensions and the base dimensions. If my guess is right, then if you've any problems ordering from the USA, an E11 base with a 230 volt 15 watt rating will probably fit OK and be available here and give the same sort of illumination level. Also last forever at that sort of downrating.
It would be way too dim.
NT
Right, he wants 230v 30w.
Any 230/240v filament bulb on 110v would be way way down on efficacy, and be no use.
NT
I'm assuming that the filament resistance is constant, in which case the power draw for a 230v 30w bulb on 120v would be about 7.5w. Am I missing something?
R varies over a ratio of 8:1 for typical filament bulbs. But more important is the filament temperature. When one is underrun, filament temp falls, and efficacy plummets fast & hard. The result would be more a glow.
NT
yes. Thermal coefficient of resistivity.
Current will in fact be a lot higher.
Correct. decent heater, not much light.
Plus the fact that even for a tungsten blub run normally, the energy peak is in the infra-red, below the visible range. Under-running just shifts the peak further down.
Might it be easier to fit a transformer to the lighting circuit and fit 240V bulbs? It would certainly make things easier in the future.
Tim
Let's see if I understand this correctly. Even if the bulb did dissipate 7.5w at 120v (and presumably the power would be lower than that, because the filament resistance would be higher than when the bulb is used with 230v), this would give a filament temperature much lower than when the bulb is dissipating 30w, causing more radiation to be emitted in the non-visible range (infra-red). So it seems I was wrong twice.
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