Ballast or Bulb?

Say, what's the symptom of a bad conversion bulb? I have a 400w hps ballast (from HTG), a mh conversion bulb, and a hps bulb. I used the conversion bulb for a couple grows, switching to hps when I flipped the lights to 12-12. This last grow, however, using the conversion bulb resulted in the ballast buzzing louder than normal and the light popping out then returning after a few minutes. The hps bulb continued to work fine.

Is the problem the bulb or something to do with the ballast. If it's the bulb, I'd like to buy a new one; I liked what the mh did during veg. But I don't want to waste my money. If it's the ballast, I'll just have to suck it up and replace.

Any ideas? Thanks.

Digital or magnetic ballast? cn

It's a magnetic.

Magnetics can be repaired. The igniter or capacitor might be wonky and can be changed out.
Unfortunately, i don't know enough about'm to tell you from the symptoms which of those two is more likely to fail. Maybe some old hand with electrics will chime in? ~hint~
Conversely, if it misbehaves with the MH but not the HPS, I'd lean toward the bulb starting to fail.

Well, normally when your trying to diagnose a problem you start with the cheapest solution. In your case, replace the bulb first, if that doesn't fix it then you know it's the ballast, problem solved, and you have a spare bulb.

Thanks for the replies. Looks like I'll shop for the bulb and see what happens.