My ballast for my fist tank blew a few times... Reason unknown. Cost of a new one is ridiculous... I took an old blown compact fluorescent bulb and used the internal circuit instead.... Months later and still working.
1.) Simple as this: Remove the aluminium piece and cut off the the wires. Keep them as long as possible. These two wires will connect to your 220V mains supply.
2.) With a knife, split open the bulb's casing...Notice 4 small wires connected. Cut off as long as possible. Two on the left goes to one side of aquarium light, and the two on right to the other side.
3.) Fit all in a small container and seal.
4.) Simple Instuctable, but well worth to know, as these original Ballast's are expensive and my trick works just as good (or better) with an old blown bulb.