Aw man those are F90T17s!!! Until I read the title I was getting ready to gather up my electrical tools and ask you where you saw this and grab a truck and start grabbing these puppies.
I want to get some lamps for my fixtures. I can't find them anywhere! At least not at a less than asinine price. the few left out there go for like $100 a lamp.
Oh wow that's a bit of a hike lol. There was quite a few abandoned mill buildings along the route 6/10 connector but most have either burned down or were torn down.
Yeah the light from them is very diffused and low glare. The large diameter tube gives them a low surface brightness. they don't last long though. Like 3000 hours I think. Modern T8s last 24000 hours. T17s did not exist in the 20s. They came about around 1940 and the fixtures were discontinued by the end of the 40s once slimline T12s came around.
Ok, it throws me for a loop, most building that I see have them are 1920s but hospital code must of made them go back and put them in, for that short of a time, lots of hospitals put them in.
Ah so they're rated to last the same length as the preheat T12s then. Most that I've seen are rated at 9000 hours. Yeah it's too bad no one ever invested in T17s. An F100T17 with a triphosphor coating would probably be VERY bright and with beefier electrodes, they could make one to last longer than T8s! They could have also come out with a special rapid start ballast for them. But the lamps use more materials so they're more expensive to make so they wanted to keep them as cheap as possible.
Yeah these tanks rarely ever die. Stuck starters usually are what kills older preheat ballasts (since it short circuits the electrodes of the lamp rather than the current actually flowing through the tube between the electrodes) but these big T17s rarely seem to get hurt by stuck starters. Other collectors have said they've got T17s that had stuck starters for YEARs and with new lamps and starters, the fixtures fired right up!
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Until I read the title I was getting ready to gather up my electrical tools and ask you where you saw this and grab a truck and start grabbing these puppies. 
There was quite a few abandoned mill buildings along the route 6/10 connector but most have either burned down or were torn down. 
T17s did not exist in the 20s. They came about around 1940 and the fixtures were discontinued by the end of the 40s once slimline T12s came around.
