I just insatlled 5/300W/120V outdoor quartz light bulbs for the 3rd time in 6 months. They are installed on an apartmnet complex. The bulbs that have all blown look the same. The tubes are black inside like they received alot more than 120V at one point. When I insatll the lights Im very careful not to touch the glass with my fingers. I installed a surge surpressor breaker in the panel feeding the lights the 2nd time all the lights blew, but now that they have blown again Im out of ideas.They are the only thing on a 20 amp circuit. Any help would ge greatly apreciated.
I don't know if moisture would cause the "black marks" that you described, but would lead to premature bulb failure if they got wet. Check the gaskets around the lights, if all else fails to provide an answer.