Problems with new MH Bulbs not working

[jezzeaepi]

Howdy All,

Was hoping someone could give me some advice on troubleshooting a problem I am having with some new MH bulbs.

I have been using 250W - 20k Radiums for about 7 years now. It was time to replace them again, so I picked up two new bulbs this weekend. I installed both bulbs before leaving for the day, and came home to find that neither one was working. One bulb was completely cool, and showed no signs of problems other than it wont fire up. The other bulb was very hot to the touch, and the inside of the bulb is now covered with a silver/chrome coating that covers 70% of the bulb. I took out both new bulbs, put my old bulbs back in, and they both fired up just fine.

Any ideas of what is going on here? Pretty confused how both bulbs could fail to start, with one of them seeming to have catastrophic failure to the bulb.

Thanks,
Jesse

 

[kevinpo]

Hello,
Are these mogul mount type or double ended bulbs? Are they also Radium brand?

Regards,
Kevin

 

[jezzeaepi]

Howdy Kevin,

These are mogul mounted and Radium brand. I am using a PFO 250W HQI Dual ballast, and some lumenarc minis. Been using this combo with Radium 20ks for about 7 years.

Thanks,
Jesse

 

[kevinpo]

Hi Jesse,
Radium bulbs should run on HQI type ballasts (M80) and pulse start (M138) for the 250w. They will appear much more blue using the M138. It is actually a 270W bulb. Bulb mfgs change bulb design from time to time which can change which ballasts work best. In your case the old PFO ballasts have a capacitor that deteriorates over time. Bulbs that have been struck many times light more easily. New bulbs need about 80 hours (or about a week) to burn in. My guess is that the capacitors need replacement in your ballast. If you know someone with an electronic ballast (or maybe your LFS) can test the bulbs for you to eliminate the possibility of faulty bulbs.

Regards,
Kevin
PS: If you need a capacitor I may have one or know where you can get one.

 

[jezzeaepi]

Howdy Kevin,

Thank you for your response. Would the capacitor deterioration cause the bulb to "break"? I mean, it didn't physically explode externally, but the inside of the bulb is all messed up and has a silver coating on the glass. I don't think it will ever be useable again. Ill try to post a picture when I get home.

Thanks,
Jesse

 

[jezzeaepi]

the silvered bulb

 

[kevinpo]

Hello,
It appears the inner envelope has ruptured. The bulb is not useable. I have not seen that happen from a bad capacitor (I'm not saying it's impossible just I have never seen it). I would suggest removing the current bulb from the socket that it was in and checking the small tab at the bottom of the socket to see if it is burnt or melted. A poor connection can cause that condition. I have seen the thickness of the tab on the end of the bulb that contacts the bottom of the socket vary enough to make bad contact and cause bulb failure. Hold the old bulb and the new one next to each other and check the thickness.

Regards,
Kevin