I have a pair of DeWalt DC527's (battery powered hand-held florescent lights). The reason I have two, is that one doesn't work! I'm too lazy to go through, what I assume would be, a difficult returns process; so I'm fixing it myself.
The not so functional light does sort of work; the bulb glows; but does not fully light. I may have narrowed down the problem: the not so functional light is running at twice the frequency of the good light. I'm working on a circuit diagram (for diagnostic purposes), hopefully I can determine which components create the AC switching frequency, and test them next.
I may have given up trying to tape and skim coat my walls upstairs, I'm just not very good at it. I found someone to hire to help me with the work. I hope he calls tomorrow.