So your daylight fixture has broken.
The symptoms may be various, in my case the ends of the tube burn orange. First thing you have to check is the tube bulb itself. If after replacing th bulb still doesn’t light up, then check the ballast. My fixture uses electronic ballast lighting up one 36Wt lamp. Replacement ballast cost me about 5 USD. I also was fool enough to throw out the orange burning lamp, thinking it burn out, so I also had to buy a replacement lamp for 1.5 USD more. Well, it may be feasible to completely replace fluorescent bulb with led tube, however, T8 led replacement tube will cost you over 30 dollars, while I paid only 6.5 for fluorescent lamp and ballast. At as ballasts normally work for years, next time I will have to spend only 1.5 USD for the lamp. So in my case, led tubes are not economically feasible yet, and they have too monochromatic light spectrum which I don’t like much. But if you decided to retrofit your existing fixture with modern LED bulb, I’ll show how to connect a led tube in an old lamp. First, you have to understand which type of ballast your fixture uses. The oldest ones have choke and starter, remove them both and connect together two pieces of the wire that was going in the choke and out of it. Now insert the LED tube and it should work right away. Newer fixtures have electronic ballasts and the wiring is more complicated. Cut away the electronic ballast, and swage or solder the tips of all the wires. As my ballast was broken anyway, I decided to disassemble it and cut the already soldered wire tip from the board. This saved me the joy of standing high up the ceiling, with hot solder dipping on my junk. I ended up with 6 wires: 2 electricity input, and two pairs of output for each of the lamp tube ends. If you are retrofitting with LED lamp, you should also cut the two wires that connect both lamp sockets together, of cause if the rapid start is wired that way. After that, take one of the two wires going to the socket from the ballast, and connect it with one of the wires electricity comes from. Connect the other electricity wire with one wire from the other socket. It may be required to add pieces of wire if existing ones are too short. Insert the LED tube and it should light up right away. Replacing electronic ballast is also a relatively simple procedure. Luckily, the new ballast I purchased is longer than the broken one, that’s why I don’t have to make the wires longer. Connect the wires according to the schematics. For some reason, most lamp equipment uses idiotic type of connector posts, so make sure the wires are secured in place. In my replacement ballast the posts are very close to each other, so I had to additionally insulate naked wire tips from each other, just to be on the safe side. Let’s check. Everything works. Now carefully place the wires and the ballast back inside the fixture, and assemble the rest of the parts back. By the way, in some cases you may re-use the ballast inside a burn-out compact fluorescent bulb, if the ballast is still operational of course. You probably won’t find a 36Wt lamp, but 18Wt compact lamps are quite common. The ballast from such burnt bulb has been working for several years in the harsh moisturized conditions of my bathroom with constant flips of the switch, which is also not good for fluorescent lamps.