I have a 250w HPS that is cycling bright and dim. The magnetic ballast kit I used is brand new, as is the lamp. Whenever I turn on the lamp, it warms up normally than dims down and turns a little more orange. This is by no means turning off. In its dim state the light is still blinding, just not as much as it should be. I found the lamp stays dim for 43.5 seconds and is bright for 39.5. I used a stopwatch and found these times are consistent within about a quarter of a second. This makes be think the ballast might have something to do with it. Any ideas?
I decided to check the voltage across the lamp as it cycles. Didn't have a chance to check the open circuit voltage however. When the bulb starts it's bright phase, the voltage immediately drops to 80v and continues to 78 over a few seconds. The voltage slowly climbs to 95, and then instantly dims. The voltage then jumps up to 105v and continues to 112 over a few seconds. The voltage then slowly drops to 90v before starting the cycle over again and brightening up at 80v. +-12v from the nominal 100v is quite the variation. The lamp was a cheap one from ipowergrowlight.com, but I am inclined to believe that is not the issue considering it seems to work at full capacity half of the time.