I have an odd lighting problem. Banks of 277V drop in and two of them strobe if they both are hooked up. At one time there was a master slave setup but the lights were retro fitted. I changed the ballast and lamps and checked the tombstones did not find a problem. From the looks of it the ballast have been changed more than once, and I don't think they ever worked right. I plan to run new feeds to the lights but was curious what was causing the problem. Rod