Originally posted in r/LampRestoration in ~2018

I have a large aquarium with a few fluorescent light fixtures. I noticed that one had started to occasionally take a few flips of the switch before it would turn on. Finally it just quit for good. I suspected the ballast, since the bulbs never flickered or anything. Swapping in a known good bulb from one of the other lights confirmed it, the issue is something other than the bulbs, and there isn’t really much else other than the ballast.

Didn’t take a proper before pic, but all that’s been done here is removal of the bulbs and the plastic clips that hold the reflector to the black housing.

Reflector removed from the housing. Everything is attached to the backside of the reflector, the housing does literally nothing beyond, well, housing everything.

No pics of the multi-meter in action because I only have two hands. I could either measure the voltage or hold the phone to take a pic, not both at the same time. Voltage measured ~115 on the black and white wires coming in from the outlet, but nothing on the wires going to the bulbs. This confirmed my suspicions.

Fluorescent fixtures are not my strong suit so I labelled all the wires. In retrospect I didn’t really need to do this.

The other side, and more notes on which wires go where

Close up of the old ballast. The label has a little diagram. This is where I realized that I maybe didn’t need to label all the wires.

New ballast. New wiring diagram. Different color wires. All that labeling work I did was in vain. I had a hard time selecting a replacement ballast, there may as well be an infinite number of choices nd like I said this isn’t my strong suit. I wanted one for two T8 bulbs, and the same number of wires as the original. The Fxx number refers to the length of the bulb. I’ve got F30 bulbs. This ballast is labelled as working with F25 bulbs and F32 bulbs (as well as some others. I decided that since 30 is between 25 and 32, this will be fine. Makes sense to me, hopefully I’m right and I won’t be drastically shortening the life of the ballast.

New ballast installed and wires reconnected to the sockets. The new ballast is quite a bit smaller than the one it’s replacing, so I used one of the existing holes, and made a new one for the other mounting tab.

Success!