Please don't set about modifying mains-powered electronics unless you know exactly what you're doing, which clearly is not the case here. A darkroom fire and/or electrocution is not worth it.
If it's a 19V bulb, the cheapest and safest option is to use a laptop power supply of sufficient power rating. It will even have better regulation than the old magnetic supply!
If it's a 24V bulb, you can buy 24V switching power supplies off eBay for peanuts, well under $100 for 300W+.
The faceted reflectors on some bulbs will be irrelevant for an enlarger; they're just a slightly different approximation of the parabola behind the filament. If you're replacing the bulb with a new/different kind, what matters with a condenser enlarger is that you get the filament in the exact same spot or the condensers won't be focused right and you will get uneven lighting of your negative. If you're building a replacement bulb mount, include some fine sliding adjustments to get it all aligned. Don't put a higher-powered bulb in the enlarger unless you upgrade its cooling.
Last edited by polyglot; 02-16-2013 at 06:50 PM. Click to view previous post history.