Believe me, I feel your pain. I have the same problem with a store full of F12 U tube fixtures. Some work, some don't, all are daisey chained also.
I replaced tubes, used another brand tubes, used energy saving and full wattage, replaced the ballasts, checked ground and voltage all without success.
Out of despairation I take the ballast (electronic), both tubes and the strip that holds the sockets out of the fixture and bring it all back to the shop.
I set it on a wood workbench (remember, not even a ground). Connect the ballast leads to a cord and plug and it works perfectly. Use ANY of the tubes I tried back at job and they now work perfectly too. I put some aluminum foil under the tubes to simulate the grounded fixture sheet metal. I ground it to the ballast case and the receptacle ground. Now they light even faster.
I can't see anything wrong with the sockets or wiring but I replace the sockets just so I can say that EVERYTHING electrical is new.
I bring it back to the store and now it's been working since. Don't ask me why. I'll let you know what happens with the others.
-Hal
[This message has been edited by hbiss (edited 02-19-2007).]
