Well I figured out why one of the vintage shoplights in my friend's woodshop is so flickery the other day...I finally opened it up and discovered none other than an obviously-replacement "US Fluorescent" LPF ballast in there! My friend even knows what a full-power Universal Therm-O-Matic or Advance Kool-Koil is, so we were laughing at the pathetic .75 amp line current! (Would be less but it's LPF!) I suggested we stick in 34 watt lamps since those seem to do better on those ballasts than F40s and even if they cook the ballast it it's an excuse to put in something more robust. After removing a GE Watt-Miser from another fixture to pair it up with, I tried sticking in an Ace F40SP41 in it's place, and was having trouble. No sooner than I remarked I didn't want to break a socket, POP! Friend was like, "It's fine, it's fine" but I'm still planning on bringing a socket on my next visit and offering to fix it...doesn't matter to me since, like Mike, I might be getting these fixtures in the future so any lamps/ballasts/sockets will likely be coming back to me.
In the past I've noticed all these fixtures except for one look like the lampholders have been replaced so I wonder if the ballasts are all crappy LPF ones? (Except for one really vintage looking one that's REALLY bright and warms up quickly in cold...I sense a nice full-power ballast in there!
He is considering replacing the fixtures with something else and giving them to me...he would like to move away from linear fluorescents and we're talking spiral CFLs with lots of ceramic JB sockets mounted to a board or something...possibly brighter and less flickery. (Power usage isn't an issue, could use incandescents too!) Any ideas? We're NOT going with cheapo T8 shoplights though!