David and all,These 120 mA beasts were indeed used for lighting, but not for neon signs. They're "cold cathode" transformers. They used to be quite popular for indirect "cove lighting" for high-end homes and numerous commercial buildings. The gas tubes were larger-diameter (18, 20, and 25mm) argon-mercury vapor tubes with various phosphor colors. Think long straight or custom curved neon sign tubes, on steroids. The higher discharge current provided brighter illumination needed for indirect lighting applications. Google images of "cold cathode cove lighting" to see examples of this lighting technique.
A typical 15 kV unit was rated for 1650 VA (regular), or 1000 VA (high power factor), and is a bit wider and much taller than a typical 15/60 NST. Think BIG. A 15kV unit could power up to 120 feet of tubing. It typically weighed 75-85 pounds (about twice that of a typical 15/60 NST). These behemoths are becoming increasingly scarce as flexible multicolor LED strips and mood controllers are often used instead for new designs.
I've only seen one of these transformers in over 25 years of coiling, and I jumped at the chance to get it. Following is a spec sheet from a 2001 Magnetek catalog showing a variety of them ranging from 5 - 15 kV.
http://www.capturedlightning.com/photos/NST/Cold_Cathode_Transformer.pdfAlthough 5kV, 7kV, 9kV and 10kV/120 mA units are still available, 12kV and 15kV transformers may no longer be manufactured.
Bert David Rieben wrote:
Russell, I believe that those cold cathode type transformers would have mostly seen use in the neon sign shop, such as for bombarder duty and not really much use ‘in the field’. Some of the old shops actually used a pole pig for bombarder duty. Most of the old style, iron cored NSTs that were designed for use in the field were rated at 30 mA, or even less, with the 60 mA rated ones relegated more for use in the colder climates. At least, that’s what I was led to believe. Any that were rated at 120 mA or more were probably designed for in shop use only. Maybe someone with experience in neon sign maintenance could weigh in here? David Sent from my iPhoneOn May 1, 2018, at 6:18 AM, Russell L Thornton <russell.l.thornton@xxxxxxxx> wrote: Hi David and Peter, I don't know about the "gas discharge" part of the description but I have one of those beasts rated at 120 mA and 15 Kvolts sitting in my garage. I did not realize they were that rare. Also not sure about the Arctic climate part either since I got this thing here in Florida. I have not put it to its intended use yet for a coil but I have tested it. The guy I got it from had it set as a Jacob's Ladder. Performs well! RussHi Peter,Yes, though they are a rare animal indeed, there were a few 120 mA gas discharge ballast transformers out there, and I believe they were available in the typical NST voltage ranges (6, 7.5, 9, 12, and yes 15 kV.) >Come to think of it, I can?t recall ever actually seeing one in person myself, just pictures. Don?t know if they even manufacture these type of transformers any more? Seems like IIRC, they were referred to as ?>cold cathode? transformers. Besides possible bombarder duty in neon sign fabrication shops, these beasts would have probably only seen use in the field in Arctic climates, where subzero ambient >temperatures would impede the noble gases from ionizing as readily, thus requiring more startup current. I seem to recall even seeing a 240 mA! NST, (but only 7500 volts) on eBay once. Many neon type signs >are beginning to be replaced by LED based signs and the few that still utilize the ionization of rarified noble gases to obtain their luminosity use those smallinver ter transformers instead of the old iron core >style, which are unfortunately useless for coiling.I would be willing to wager that if you could even find one, it would likely cost you considerably more than a decent 10 or 15 kVA rated pole pig.Another David_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla
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