We have a couple of old fluorescent fixtures in our basement, each holding four 4-ft long T12 bulbs. After several weeks of slow starts, the lights finally stopped coming on in one of them so while we eventually will replace the fixtures with LED ones, I went ahead in the interim and purchased four new bulbs. I put two of the new bulbs in the two adjacent slots on one side of the fixture, thinking that it needed both bulbs to be in at the same time. When I turned the fixture on, one of the bulbs looked like it was trying to light up, the other did nothing. So I concluded it was the fixture and removed the new bulbs.
Now I am wondering if I was too hasty in that decision: Is it possible that all four bulbs have to be in place for them to light up or maybe the two inner ones or the two outer ones have to be in place, instead of the two on one side as I tried. Is there some standard in what these fixtures expect?