ballast

Fluorescent light ballast limits the current in the tube which is necessary for stable operation. Wikipedia has an article which shows some pictures (but does not fully explain its operation).

You might find it easier to just replace the entire fixture, they are generally not very expensive.

Either way, an electrician is warranted (although in the home it could be done by a competent handyman).

As luck would have it, I used to work in a plant that made electronic ballast. I did failure analysis on them. So I know ALOT about them and happen to have been an Electrician....Shocking personal fact...LOL...

Anyways, Electronic ballast are metal box looking things with wires sticking out. They come in different voltages and sizes. They are in many of your industrial type lights in the ceiling or light fixture. They are sold at many hardware/home supply stores. An Electrical supply place may be the best place for specialized ones.

The price range isn't that high. I am thinking less than $40. It really depends on size and type. There are two types of ballast which electronic are the majority of. They are easy to replace. The job should take about 1/2 hour depending on access.

Honestly, my opinion is your better off replacing the whole fixture than just the ballast. Ballast types expire for a reason. A smaller ballast doesn't sound like the right choice. Knowing what I know, I would just replace it all if possible. The electrician would be able to install it easier and better product in the long run....

By the way, ballast are designed to "burn" out when they fail. This NOT a fire hazaard. They are encased in tar or other material inside so they don't make a fire. A bad ballast can't be fixed. Hope this helps...Who knew my ballast knowledge would come in handy one day???LOL!