MH bulbs vibrating and shutting off...

[fivel]

I have a light fixture with 3, 250W MH single end bulbs. I bought the fixture brand new from ebay and everything worked fine on arrival. I had a stock bulb burn out about 2 months after I received the fixture, so I bought 3 brand new bulbs and kept the remaining two as backups. Lately I have noticed that the middle bulb will vibrate and flicker right as it tries to turn on, but then will kick off. It will start this again about a minute later and after about the third or fourth try, it will actually stay on and warm up. Today I noticed that after 2 hours of trying it still had not managed to actually stay on. I turned off all of the MH's and let them sit for about 10 minutes. I turned them back on with the same result with the middle MH and the far left MH started to vibrate and flicker as well, although finally kicked on after the 2nd attempt.

I did find a thread on here that was talking about "corrosion on the pins", although not sure how that translates with a screw-in, single sided MH bulb. Any suggestions would greatly be appreciated. If the specifics of the bulbs or fixture itself prove necessary, I can post that information as well.

 

[DaveK]

I'm sticking my neck out a bit, and this is a bit speculative, but I suspect your problem is low quality ballasts in the fixture. Also, did you get "bargain" replacement bulbs? They can also give you similar problems.

I'm assuming that the "vibrate and flicker" refers to the bulb's light output, and not an actual physical vibration.

Here is what to do.

Swap you bulbs around. If the problem follows the bulb, the problem is with the bulb, replace it. If the problem does not follow the bulb the problem is with the ballast, replace it.

If you replace ballasts, replace them with quality electronic ballasts, rather that the traditional coil and core ballasts. Electronic ballasts cost a lot more, but the electricity savings will pay for them in about a year. Electronic ballasts also run much cooler.

 

[Frankie]

Yeah the problem is the ballasts. What's happening is they are cheaply built magnetic ballasts. This happens also with high end ballasts after they degrade over a long period of time. You can replace the ballast with a better one. I would recommend an electronic ballast for they have not been reported to do this after years of use. I found Galaxy to be the best for the buck.