I had been collecting failed Compact Fluorescent Lights (CFL), not sure if they can be repaired. As part of the year-end cleanup, I spent some time with these lights to decide what to do with them.
They were hard to open. Maybe you are not supposed to open them, but it was easy to cut them with a saw. Inside you will find an inverter circuit board that takes 120V AC and converts it to about 330V DC. The output is four wires, two on each side of the inverter board.
The inverter board is crammed with parts in a small space, so I wasn’t about to attempt component level repair. The fluorescent tubes (FTs) are not soldered in, but the four wires coming out of them were actually wrapped around the terminals on the inverter board. I unwrapped FT terminals from each inverter and separated them.
So now I had a pile of FTs and inverters (connected to lamp bases).
When these lamps fail, the failure is either with the FT or the inverter. First we need to find a good inverter. In my case I found one inverter that I knew was good.
Here is the picture of the connections needed to test.
The black and red wires at the top go to 120V AC, the white and green wires at right, and the yellow and green wires at left are connected to pair of wires on the FT. The pair of wires can be swapped without any problems.
Above is a picture when the CFL is powered up. Obviously in this case the FT is good. With this setup we can check each FT. I threw away any FT that did not light up.
In the picture above you can see that the FT is just starting to light up. I had a varactor so I could slowly increase the AC voltage. I noticed the FT starts to light up when the AC voltage gets to just about 55 Volts. After that it gets brighter as the voltage go higher.
In the picture above you can see that I used a simple lamp socket to provide AC power with Varactor.
Once you have a working FT, you can test the rest of the inverters. I kept failed inverters for parts just in case. Now any working FT can be paired up with any working inverter. In my case out of five lamps I threw away three FTs. Note that none of the lamps worked before.