if i disconect the igniter in my hps can i then run a mh bulb in a hps ballast?

Yes if you add a capacitor to fire the halide. There are directions out there somewhere for adding a switch and wiring this up to just switch either way.

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cool,thank you. ill look for them they must be on the net some place.

I wouldn't advise it.. It might work, but not as its intended.. Bulb life will be shortened, possibly drastically to the point of independability for a single grow, and output will be diminished at a higher power cost.. Granted a proper capacitor to atleast match the reactance will help, but while you're at it buy a proper transformer too..

Edit: Or your ballast may not be suitable at all..