gpodio Posted March 3, 2004 Share Posted March 3, 2004 Hi all, I have a used 250W MH fixture that was given to me, I finally pulled it out of the box last night and tried turning it on. The bulb fired up, a little on the dull side at first then slowly gained intensity. However after a couple of minutes it just turns off, I still hear the humming from the ballast but the bulb is no longer lit. Not having used MH before I don't know if this is something that occurs when the bulb is old and no longer of any use or if it sounds like there might be problems with the ballast. Not sure if there is an easy answer but it's worth asking seeing I'd hate to buy a new bulb and find out that the ballast is at fault. Any suggestions? Thanks Giancarlo Podio Link to comment
1fish2fish Posted March 3, 2004 Share Posted March 3, 2004 You might try directing a fan towards the ballast to see if it is overheating. I only have limited MH experience so this about all I have to add. It might work though. Link to comment
gpodio Posted March 3, 2004 Author Share Posted March 3, 2004 Thank's I'll open the fixture up tonight and give that a try. I do however doubt that heat would be an issue as the light doesn't even stay lit for more than a couple minutes (2-3). If it overheats in that amount of time I'm guessing the ballast is probably shot. What are the usual symptoms that a MH bulb is reaching the end of it's lifespan? Thanks Giancarlo Podio Link to comment
1fish2fish Posted March 3, 2004 Share Posted March 3, 2004 I don't actually suggest that you open up the ballast box. It's kind of an electrical hazard. I would just try blowing air across it. You would be suprised how much heat they can generate in a short period. I assume it's one of those large black magnetic ballasts? Link to comment
gpodio Posted March 4, 2004 Author Share Posted March 4, 2004 Well strangely enough I turned the thing on again and this time it remained lit! Perhaps it just needed to wake up after many months of storage ;-) Thank you for all your help, I'll put the fixture to the test in the next couple of weeks to make sure it works the way it should. One last question.... As MH bulbs get old, what starts to deteriorate first, spectrum or amount of light output? Link to comment
qfour20 Posted March 4, 2004 Share Posted March 4, 2004 The first signs that a mh bulb is getting long in the tooth is spectral shift. This is not an easy thing to measure in a home setting. The easiest thing to do is to watch for nuisance algae. When you start seeing hair algae or cyano outbreaks, there's a good chance that your bulb needs to be replaced. Hope this helps, and good luck! -q Link to comment
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