How can I tell whether I have a magnetic ballast or an electronic ballast?
While commercial test equipment is available for determining whether a magnetic ballast is in place, there is an inexpensive do-it-yourself test that can be done with your cell phone!
Just point your cell phone camera at the lamp, and take a picture. If the image displays dark bands or stripes, your fluorescent lamp is driven by a magnetic ballast. A modern, electronic ballast drives the lamp at a much higher frequency, and a picture of these lamps will be clearly different, without such bands.
The image below shows a T12 fluorescent lamp with the tell-tale bands generated by a magnetic ballast:
The image below shows a T8 fluorescent lamp with a steady glow indicating that it’s driven by a modern electronic ballast.