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Old 9th Feb 2018, 12:47 am   #7
broadgage
Nonode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
Default Re: Lamp Limiter Bulbs

I think that you are mistaken in saying that these lamps have carbon filaments.
Almost all these "vintage style" but recently manufactured lamps have a tungsten filament that is a reasonable copy of the early types of tungsten filament lamp, used before coiled filaments.

Many vendors on ebay and elsewhere describe them as "carbon filament" but they are wrong ! If in any doubt, a very simple test will prove this.

Measure or calculate the hot resistance when the lamp is lit at about nominal voltage.
Now measure the cold resistance with a test meter.

In the very likely event that you have found a true carbon filament lamp, then the cold resistance will be higher than the hot resistance.

In the much more likely event that you have a vintage style lamp with a metal filament, then the hot resistance will be much higher than the cold resistance.

True carbon filament lamps of recent manufacture are now very hard to find.

"Vintage type" but recently manufactured tungsten filament lamps are very popular and widely available.

LED copies of the metal filament types are also widely available and are IMHO rather attractive, but no good for a lamp limiter.
LED copies of carbon lamps also exist but are less common, again attractive in some situations but also no good as a lamp limiter.
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