light fixture half burned out

Ok, so I have a 55g tank, and the hood is split into to pieces that meet in the middle. The light itself has 2 bulbs, and one of them is not turning on. I replaced the bulb and it didn't come on either. I then put the new bulb in a different fixture and it worked just fine. So it must be that half of my light fixture. It's now humming loudly whenever I initially turn it on. Is there a piece in my light fixture that I can replace instead of buying a new light? Perhaps a fuse?

Any help would be appreciated.

 

The ballast may be the problem. Sometimes they are found on the outside of the housing right near the light. Look for a little cyclinder white or black in color. If not, then you may need to look inside the housing. It will be a cylinder or a little box with wires coming out of it. Take it to the local hardware store and replace it for four of five dollars.
I hope that helps a little!

 

The ballast will be black and square or rectangle in shape. The white cylinder is a starter and will probably have the markings "FS-2" on the side. Very few aquarium lights have a starter but if it does it would be the first thing to replace. They cost about $1.50 each. If it is the ballast it should cost between $5.00 and $8.00. With heavy use a starter will last about 2 years. A ballast even under heavy use will last generally about 8 years. If you're not sure about the wiring on a ballast get someone who knows how.

 

Awesome, thanks for your imput. I replaced the starter, and now the light works, but there is now a loud humming coming from the light. I'm not too good with wiring, so I checked the outside of the light, and when I tilted the light the humming stopped. When I put it back, it started again. Does this sound like a problem with the ballast?

 

It's possible but it sounds more like a poor connection somewhere. Make sure the new starter is seated well. Check the wiring connections at the cap locks and the bulb recepticles. Most likely the problem is at the recepticle. Either the bulb is not seated well or there is corrosion on the contacts where the bulb snaps in. Corrosion on the contacts is very common in areas of high humidity. ALWAYS UNPLUG the fixture completely when working on the light. It is also advisable on fixtures with a starter to remove the starter when working on the light.