Hi, I replaced my florescent with a mercury vapor bulb today. Self ballastered. I positioned it above the basking platform, and measured the temperatures below it after it was on for like 30 mins. It was a little too hot. I noticed that the ceramic socket was quite hot too. So I switched it off, and positioned it higher up above the platform, and switched it back on again. When it went on, I heard a slight rattling sound, almost like the sound when you switch on a florescent light in a garage, for about a second or so. The light switched on as normal, bright as ever, hot as before. Didn't think much about it then. Now, I just read online that SBMVBs can burn out when you switch them off and then on again before they are 100% cooled off in temperature! In that website, it says that the bulb will completely burn out, no light, no heat, no UVB. But I can't help but wonder what was that fizzing/rattling sound?? It lasted like half to one second. Can it be that the UVB emitting mechanism has burned out but it still produce the same amount of light and heat??? I am not talking about a decay over months here. This is a brand new bulb. As long as the bulb switches on, it should still be emitting UVB, right? How can you tell? I can't really get a UV meter now.