WARNING: Power supplies contain high voltage. Monkeying around in them can be fatal. Always unplug before touching anything, and familiarize yourself with high voltage safety. If you are not comfortable doing this sort of work, please don't do it.
I love my LulzBot Taz 4, but recently, the power supply started squealing like a pig, and generally making horrible noises, suggesting that the cooling fan was dying a slow and painful death. I knew I had to fix it right away.
A thorough cleaning of the stock cooling fan didn't fix the problem, so it became apparent I would need to replace it. I scrounged around for a suitable fan, and found this Cooler Master CM12V, which is a pretty standard CPU cooling fan for a desktop PC. The CM12V had a 3-wire plug, while the original Taz fan only had 2 wires. I chopped both cables and spliced the wires together (red to red, black to black), disregarding the extra (yellow) wire on the CM12V. I twisted the wires together and soldered them, finally wrapping them in electrical tape to prevent shorts.
At first, I fashioned a primitive cardboard fan mount, and held it in place with electrical tape. This worked long enough to print the ABS version, which I immediately installed in its place.
So far, it seems to be working fine. I use my Taz pretty heavily, and the factory fan lasted about one year. If I have to change the fan every year, I want it to be accessible, standardized, and easily swapped. This system is much better (IMHO) than the stock fan, which I actually broke trying to remove, because it refused to come off of the top cover. The power supply also seems to breathe easier in this open configuration, meaning it outputs more heat through natural convection and doesn't need to turn on the cooling fan nearly as much.
Don't leave yours open like this if you have small children or pets that like to climb around on things -- they could be electrocuted. Otherwise, I think this is a great solution to the problem of having an unreliable and unserviceable cooling fan.
Printed in black ABS. Assembled with #4-40x1" brass machine screws, nuts, and washers.
Make sure to bolt those screws on hard enough that they don't fall into the power supply and short something out.