BulbCollector Forums
BULB DISCUSSION BOARDS => Antique Bulb Discussion => Topic started by: Chris Kocsis on October 05, 2000, 09:15:00 pm
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Hi all, here's a bulb I just got and I wonder if anyone (James?) can tell me what the "rectifier" on the label means.
The bulb is about 7 inches high with a mogul screw base. Edison Mazda etch on the glass. The filament is a single thick silvery strand. I take it from the label it's intended for series burning.
Please forgive the lousy pictures, I'm capable of much better but didn't pull out the good lamp. Thanks for any info!
(http://www.radix.net/~chrisk/rect2.jpg)
(http://www.radix.net/~chrisk/rect1.jpg)
(http://www.radix.net/~chrisk/rect3.jpg)
[This message has been edited by Chris Kocsis (edited October 05, 2000).]
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Hmmm...yeah that is an unusual lamp. Judging on the filament, bulb, and mogul base, I would say that it closely resembles a series streetlighting lamp. Series streetlighting lamps with tungsten filaments from that time had the same assemblies, to my knowledge. Also, your bulb has the somewhat rare cotton fiber getter, which is located inside the hollow end of the glass arbor. These were employed in high wattage Mazda B lamps around 1912-13...in wattages of 150 watts and up. These were eventually replaced by the Mazda C lamps around 1913-14, to my best knowledge. Sorry...about this lamp being a rectifer lamp...I can't be of much help...but hope the info I provided helps you in any way.
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Hi Chris, I'd agree with Dave that this looks like a series streetlighting lamp, but I don't have any idea what the rectifier bit is referring to. Perhaps its for an old DC streetlighting system? But quite why a special DC bulb would have to be made I do not know.
BTW Dave - do you have any more info about that cotton getter in the glass cane? I have a few books on lamp getters but this is one I've never come across before and I'd love to know a bit more about it!
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I assume that the lamp was made about 1912 as the stem structure is that one designed for Skaupy's getter. The cotton was probably used to contain the powdery getter. See Howell & Schroeder, page 132.
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Thanks to Pete, I have a little more info on series street lighting lamps. Quoting freely and adding to what he said (any muddling is mine):
Some street lighting systems were (and some still may be, or were until recently) operated on DC. They began as arc light systems, using high current, where the goal was to maintain a constant current in the system rather than a constant voltage.
The more lamps on a circuit the higher the voltage required to keep the current the same. They used moving core transformers for this. The voltage is less for the smaller wattage lamps, but a 1,000 lumen lamp usually runs at about 10 volts for the proper current rating. Higher lumen lamps need more voltage. The drop across each lamp can be different based on the size, but the regulator keeps the entire circuit at the proper ampere value.
Incandescent lamps were made for use on these systems and consequently are rated in amperes (and candlepower) rather than volts. The most common current rating was 6.6 amps but there were 4, 5, 7.5, 10, 15, and (judging from a lamp I have), 16 amp lamps.
If 60 candlepower seems small for a street light, remember that gas lights did not put out much light so their replacements did not need to either. The small wattage lamps were usually used in alleys.
These current-rated lamps all seem to have mogul bases. Looking through my bulbs I see I also have a tipped 7.5A one with a short coiled filament, a similar tipped 6.6A one, and a tipless 6.6A with the same filament construction. Here's a picture of the 16A one (my interpretation of the marks on the press), which is about 13 inches long and tipped:
(http://www.radix.net/~chrisk/bigst1.jpg)
(http://www.radix.net/~chrisk/bigst3.jpg)
[This message has been edited by Chris Kocsis (edited October 10, 2000).]