i made a vaporizer once out of a automotive cigarette lighter, some glass stock and a ac/dc converter.
It worked, but got too hot, so i broke down and bought one, best investment ive made yet.
The amount of bud i smoke is way less now with the vap, just buy one if you can, you will be glad you did. AND it pays for itself after a few months of use with all the bud your gonna save. ( gotta hit the bowl every now and then for the funky flavor, vaps taste fine, but bowls are better for good genetics, but they waste bud)
cool, disco, now i'm about to spend an hour looking at lights on ebay! lol, I'd love to have a digital ballast, maybe i'll dig up a thread explaining them so i have a clue.
I hear nothing but good things about CMH. I read they may operate a little cooler than HPS. If there's anything remotely negative, they may promote a bigger leaf to calyx ratio. If you have a strain that throws heavy trichs on bud leaves, this might be a plus.
If you get a compatible watt size, both CMH and HPS lamps can be operated from the same ballast. You could use CMH through early flower and switch to HPS for more lumens and enhanced color.
I know a 400w HPS ballast will operate a 400w CMH bulb. Not sure about 250w. A 150 watt CMH bulb requires a pulse-start metal halide ballast. Hope this helps.