# Neon transformers



## Big John (May 23, 2010)

I know roughly speaking, as the distance increases between the electrodes, you need a higher voltage to ionize the gas in order to light the sign. So longer tubes get higher voltage trannys.

The amount of current you pass depends on the total volume of gas and how brightly you want it to glow. The transformers are inherently current limited so there's not a risk of short-circuiting them, but I think that passing too much current can affect sign life expectancy.

While I know there are loading charts for tube length and diameter, my understanding is that a lot of it is literally trial-and-error: They ball-park a transformer and see if it works.


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## Electric_Light (Apr 6, 2010)

farlsincharge said:


> I have been dealing with some neon sign guys to help me over the phone. (rural area) and I have come to the conclusion that they are idiots.
> 
> The 9kv transformer *wasn't big enough *and has an open secondary. Just wondering what to replace it with.
> 
> The transformer the neon guys sent me as a replacement is 12kv and *even smaller*, so it is going back.


I don't really know what you're talking about. Who made this diagnosis? 
Modern electronic transformers are much smaller and lighter than old coil and core style. The size of case is not how you size a neon transformer. 

mA determines the brightness, so you match the original. 

The total length+, number of sections+, diameter- and fill gas (red+ vs any other color-) determine the voltage you need. The + /- on the end of each word indicates the direction of voltage change. 

The kV is the open circuit voltage. The voltage needed to strike the lamp is about four times the running voltage. Leaving the transformer energized with a broken tube will unduly stress the insulation.


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## Electric_Light (Apr 6, 2010)

http://ventextech.com/downloads/neon-power-supplies/outdoor/VT12030CL-120.pdf
Look at the very wide range of application. 

They're just like T8 electronic ballasts that let you run anything from 2 to 5' lamps. In the magnetic ballast days, that was not possible. 

If it still doesn't work, one of the tube segment is probably dead. Test each segment with a lamp test wand or a plasma globe toy.


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## Texas_LED_Guru (Mar 1, 2013)

farlsincharge said:


> *Can anyone explain what dictates the voltage to be used?*
> 
> Working on a sign with two transformers. The tubes are the same size and about the same linear feet for both sections.
> 
> ...


Length & diameter of tubes & if they are neon or argon filled. Also the MA rating of the electrodes & transformers...30, 60, 120, 200, etc.

Now there is such thing as "self adjusting" magnetic or electronic neon transformers taking the guess work out of load matching reducing the number of transformers.

A typical 15,000 volt 30MA transformer will do 50 feet or so of 15mm glass tube.

Note: You can almost always get more footage out of mercury doped tubes versus standard red neon.


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## Da M (9 mo ago)

Neon tube circuits are series circuits. Resistance is higher for neon (red gas) tubes than for argon (blue gas) tubes. Blue gas tubes actually contain 3/4 neon, changed to blue by addition of argon. A tiny bead of liquid mercury is added to the blue tubes to brighten their color once vaporized. This results in a lower resistance, much brighter tube. That is why these “mercury tube circuits” can be longer, in feet of tubing, than neon tubes. 
Tube size is the other main factor in matching a transformer with a given number of feet of tubing. In millimeters, typical sizes are 10, 12, 13, and 15 mm. Most outdoor signs use 15mm tubing. In sizing a circuit, each pair of electrodes forming the ends of a tube is considered equal to a foot of tubing. Processing under heat and extreme vacuum cleans the inner surfaces of tubing, then a tiny amount of gas is allowed to enter before glass is melted to seal off a new tube. 
An old, partially dimmed tube can sometimes be “burned-in,” re-vaporizing some mercury and coming “up to color.” 
Length of circuits are larger, mercury, properly processed - longer with a given voltage. Smaller tubes, red gas, and more electrodes result in that higher resistance circuit running less footage with the same transformer voltage. Current is typically either 30 mA or 60 mA on some outdoor signs.
Never take a chance to become part of a circuit. Voltage is electrical pressure, and current is electrical volume if compared with water. Neon is high pressure, low volume.


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