After 25 years, A ballast burned out and I replaced it: It lights 2,75 watt, T12, 8 ft, single pin tubes. After I replaced it , I left the cover off the fixture and let run 2 hours to make sure it worked. The ballast felt pretty warm so I measured it with infrared meter, 125 F. I know the ballasts get warm Although I never touched one directly while it was on. I have left the cover off as one cannot see the fixture. Does the temperature seem excessive ?
Ballasts are designed to run hot, around 140 degrees F.
Here's a quote from "Fire Engineering.com" that spells it out a bit.
"Overheating ballasts often exhibit symptoms. They may cause the bulb to flicker, shine, dim, or not work at all. Sometimes, smoke stains can be seen around the fixture. A light exhibiting such symptoms should be considered suspect and examined. A further test would be to check for heat from the ballast. Ballasts usually run hot, about 140 degrees F, but if one is so hot that you can’t keep your hands on it, it is likely the culprit."