Recently we had to replace our SMPS for the same reason. This had happened earlier. This time instead of giving the SMPS to the vendor we kept it with us, out of curiosity. Working into the old chap, we soon found out that the cooling fan inside it was intact.
The Cooling Fan:
The fan is rated at 12 volts. This guide will tell you exactly how to place the fan into your cabinet. The power supply for the fan can be taken from the working SMPS in your computer. You have to know a little about SMPS outputs (if you do not know already), and here is what you need.
SMPS gives output as 12v, 5v and 3.3 volt. Your fan needs 12v (rating will be marked on the fan). The standard output connectors and its output powers are given below. The images are self-explanatory.
The required 12 volt output can be taken from one +12v and one ground. Clean the old fan and place it on the cabinet using screws. Most cabinets ought to have a spare fan hole. Our fan was marked with the direction of rotation and direction of airflow. If they are not marked connect to fan to a +12v DC supply and find the direction of airflow. Make sure that you place the fan on the cabinet in such a way that its sucks air from inside to the outside. This will keep the dust out (Thanks Mathews).
The fan will have a +ve wire (usually red) and negative wire (usually black). Identify the +12v of the SMPS output and connect the red wire to it. Connect the black wire to the ground connection. We used cello-tape to make these connections. Turn on the SMPS and make sure that the direction of rotation and airflow are correct.
Now its time to close your cabinet. Congratulations!
