There are 4 total ballasts. Two of these are brand new, and two are from a long 4 bulb fluorescent light where one side was having blinking issues, so I was told to replace the ballasts. I don’t know whether one of the ballasts was bad or it was a tube issue as I ended up just replacing the fluorescent lights with LED lights. So, I believe there are 3 good ones and possibly one that isn’t good.
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