Jkirk ... Sorry, I wasn't clear enough in my original post. The solution is already built, using eight (4 per shelf) of the single-tube Lights of America fixtures, mounted on a lightweight crossbar scheme that lets me adjust the horizontal spread between fixtures, and then raise or lower the entire set of fixtures using chains and S-hooks. After my first tube failure last year I discovered the relative lack of supply and cost issues for F20T10 replacement tubes. I can get a replacement with somewhat more driving. I just wanted to know if there are: inadequate brightness / zaps tube / melts fixture / catches fire kind of problems with using a different F20 tube, since a less-expensive F20T12 fits (barely) and starts, and a (presumably?) less-expensive F20T8 would fit (easily?) and might start. Going vertical is a fun idea, but I think it would exceed the tolerance of my spouse, and I really don't want to start enclosing the shelving with a lot of reflector area ... I've got a fan running to help avoid damping-off problems and toughen up the little seedlings for the "real world"; don't want to block any of that airflow. Thanks!

Separating the pic from the description might make this difficult for people to answer. A clearer pic would help. Despite that handicap I am willing to guess that that black ring is supposed to rotate with the pins and has slots in it for the pins. They sometimes get out of alignment and have to be rotated back where they are supposed to be before a lamp can be inserted and rotated into the correct position.

You can tell which you have by how many wires go to each end of the lamp. If one wire goes from the ballast to each end (and then is spliced to the other pin right at the lamp), it's instant start. If two wires go from the ballast to each end of the lamp, it's rapid start. The lamp life difference between a rapid start and instant start ballast is somewhat significant in typical use - 25,000 - 30,000 hours for rapid start and 20,000 - 25,000 hours for instant start. OTOH, instant start ballasts use less energy because they don't energize the filaments. RS ballasts leave them on all the time, even after they're no longer needed. Sylvania says this about the financial impact : "For a normal 12 hour/day, 4000 hour/year operation, rapid start ballasts provide 7 years of lamp life while instant start ballasts provide 6 years. The 5W of coil heat costs $1.60/year in power costs for a 3-lamp ballast, or about $0.53/lamp/year. Over 7 years this would require $3.70/lamp in additional power costs to gain the year in lamp life." So, you would spend more in electricity than the lamp costs, in order to gain an additional year of life. All other things being equal, you'd be money ahead to use the instant start ballast and replace the lamp sooner. But the actual financial impact depends on what relamping labor costs you (if anything). For some people lamp disposal issues are worth considering (either for cost or environmental reasons). IMO, the best of both worlds is the programmed rapid start ballast, which uses the filaments for starting so strike voltage is lower, then shuts them off after starting. The downside is that they are significantly more expensive then either rapid start or instant start ballasts, so you don't see many of them. Rather than replace the fixture, I'd put in a good quality new ballast. I like the GE Ultramax range. Although they're made in China (sigh) they seem to have a softer start than most instant start ballasts, and they are (at least to my ears) dead silent - no audible hum at all.

Thanks, the light in question is the circular type tombstones. I broke the tube to remove it. I had trouble with another that is the "two openings" type. I put on my safety glasses and pried on the metal end caps to get that one out without breaking it. I may have all three types, among about a dozen, under the cabinets in this kitchen. I messed with them for quite a while to get them all going swapping bulbs and starters. Maybe I should have pulled them all out and replaced them with something with electronic ballasts. I may have figured out why the tubes are sticking. I discovered a box of 18" tubes in the detached garage and the pins look to be a little pitted from corrosion. Maybe some in the kitchen came from that box and suffer this same malady. This is a humid environment. I gave the pins a little rub with steel wool and put a tiny bit of dielectric grease on them. The single pin picture reminds me that I have some 8Â T12s in the garage. One is intermittent. Any recommendations for fixing it? I have enough lights in there to keep the interior temp at about 50 F despite outdoor temps in the 20s/30s (night/day) for four days. It is fully-insulated, but there are a lot of light leaks.