Thanks.I opened one of these dual 600 ballasts to service. After I replaced a burnt diode, it worked fine. I used two 1-ballast flips and it flipped both lights together to the other two bulbs and no problems. I would reccomend using two timers and flip them individually a minute or two apart in case there might be an issue. They're easy to service as any of these electronic ballasts are, the black resin comes off pretty easy.