Before you spend money replacing your tube lights, this blog post will help you diagnose whether your bulbs are really at the end of their life, or if the external ballast or driver is really the problem. Common Signs It’s Your Ballast and Not Your Bulbs details causes and signs of ballast failure as well as causes of LED driver failure. Not only does it help you diagnose the current problem, it helps you learn how to avoid encountering the same failure causes with your replacements.