I have a Lumatek digital ballast that runs both MH and HPS. There was a note included in the box that stated it might not be able to fire certain bulbs because of power draw needed to spark the bulb. The bulb you're using may be border line and only fires sometimes....?

Haven't had an issue with a solarmax MH and hortilux HPS. What bulb are you using?
greenbastard Reviewed by greenbastard on . HPS/ballast issue. Having an issue with my HPS bulb. MH bulb works fine. Went to 12/12 and changed to the HPS bulb. Was working ok, then one morning when I went out to check on the grow it hadn't come on. Juice was getting to it since when I replaced it with the MH it went on immediately. Contacted the people I bought it from and they sent out a replacement bulb. Got the new HPS bulb, replaced it the next am and it lit up fine. Went out the next am, same thing not on and when replaced with MH works, fine. Rating: 5