I was running a "life test" on 2 lamps. One a GE made ACE and a GE Mainlighter that had a bit of use.  The ACE lamp starting making a brown spot that would eventually be black. I should have changed that lamp then. It EOL-ed and also probably took out the mainlighter. It would not light when I put in a new lamp but the filament appears good.I'll see what goes when I put it in my preheat fixture. It had started some end banding. 


A perplexed Powell

This was in a 2 lamp rapid start high power fixture ceiling fixture. Well.....................when I get home the 2 lamp HPF preheat fixture will see what happens........   

That's interesting that it just failed like that. Maybe the ballast you tested it on might have some issues.

Ballast is OK. The mainlighter failed and messed up the other lamp which starts on preheat but is very unhappy. The mailighter lit and did all kinds of swirling and eventually failed.