Fluorescent fixture with what looks like a transformer with only two wires and no ballast

Question

I don't know much about how fluorescent fixtures work, but I have an old fixture from an arcade game that I'm trying to get working and it has what looks like a transformer except it only has two wires going into it and a ground, and it doesn't seem to have a ballast. Though I have never been fully clear about the difference between a ballast and a transformer.

Problem is that the transformer looking thing is making a very loud humming sound and I'm trying to fix that.

Any suggestions of what this is and if I can replace it with a modern ballast?

Answer 1

The thing looking like a transformer is a ballast.

The purpose of a ballast is to restrict current going through a fluorescent lamp, because, like all glow lamps, it can draw far more current, across a 120 or 240 VAC line, than it can survive. The ballast simply adds impedance, dropping the current. Most ballasts are simply inductors (just a coil of wire), but for small lamps, capacitors or resistors can be used. Electronic ballasts for compact fluorescent lamps (CFL) use smaller components because 50- or 60-Hz mains power is converted to much higher frequencies.

Some ballasts have additional windings (acting as a transformer) to provide lower voltage (between ~6 and 12 VAC) to preheat the filaments at the ends of the tube. Those have two leads for AC mains, and two pairs (four wires) for each tube. However, circuits with a starter, as your fixture has, can simply bypass the mercury glow-tube in between the filaments, putting the filaments in series with the ballast to preheat them, causing electron emission. Then the starter pops open, and the filaments are kept warm by the glow-tube current.

You could replace that ballast with one designed for the same lamp, rated for the same power as the lamp and for the line voltage and frequency in your locale, e.g. 120 VAC 60 Hz, or 240 VAC 50 Hz. For a 20 watt tube, see these searches on Amazon and Home Depot.

However, I'd only suggest replacing the ballast if you want to preserve historical accuracy. Given that LED's have a longer lifetime than ballasts and fluorescent lamps (particularly, I find, shorter ones), and LED's can be more efficient, it might be less expensive, in the long run, to use a 20 watt LED replacement, such as these at Walmart or Amazon.

Since that ballast is bad, and would just waste power when used with LED lighting, look for LED's that do not use the original ballast. Check carefully in the description of the product. Again, be sure to pick an LED made for your mains.

_{The links above are only for reference.}