I've been running a T5/LED hybrid fixture for about 4 years (Giesemann Aurora). It was one of the early ones that had 120V T5 ballast for 60" 80W ballasts. About a year ago 2 of the bulbs stopped firing (fixture has 2 sets of dual bulb so 4x80W T5's which work in pairs). I swapped bulbs around and the problem stayed with the pair of fixtures. I've been just using the other pair and was doing my yearly bulb swap yesterday. I decided to max out the channel that hadn't been working on the software and just try again swapping bulbs to ensure I hadn't missed anything. The bulbs that had been in the non-working fixture fired up fine in the one that had been working. Moved that bulb back to the non-working fixture and it still didn't work. So I just changed the bulb in the working fixture and tested it out. All good. Then I noticed that the non-working bulb was trying to start, then finally kicked off (I still had the slider at 100%). My question is I guess how would I check the ballasts to see if that's the problem (as opposed to loose wire or corroded contact etc). It's a real pain in the rear to take the fixture apart but it can be done. Is there a single ballast for each pair of bulbs? Not sure where to start if I want to get the other pair going.