Fluorescent lamp ballast

I have a ballast for a 27W fluorescent lamp that appears to be broken - does anyone know if there are any ballast components that are more prone to fail than others?

It's an old lamp, and it has electrolytic capacitors, which have a limited lifetime...

Is it an electronic or magnetic ballast?

If it's magnetic then the capacitors are just for power factor correction.

What are the dimensions of the tube?

A ballast has to be designed specifically to match the tube dimensions, simply throwing in another 27W ballast isn't good enough unless it's the right one.