Um... Is it a new bulb?

It sounds like it's just not firing up.
If the MH conversion bulb works fine than it's not the ballast...It's the bulb.

A conversion bulb still works with the same HPS ballast.. there's nothing different happening with a different bulb.

Sounds like the HPS bulb is not firing , aka dead.
BobBong Reviewed by BobBong on . BALLAST BAFFLED! Can anyone please give me some input on what may be wrong with my ballast. I got an hps 600 watt lighting system. When i put the MH conversion bulb in my system it lights right up and works fine, but when i switch to my hps bulb, I get a low flickering glow but it wont light up, it lit up only once or twice before but after i kept plugging and unplugging the plug and after that it never lit up again. I thought maybe it was the bulb itself so i went and bought another one, and i made the guy Rating: 5