Updated February 20, 2006

In order for ScienceMan to maintain his sanity, he must tinker. Actually, it's getting to be a fact of life for most teachers who want FUNCTIONING computers in their classrooms, considering limited technician time. The latest project is trying to bring some old Power Mac 5200 computers (75 MHz - ugh!) up to speed with faster motherboards. Apple made the Power Mac "Performa" line with interchangeable motherboards (for the most part) that can just be slid in and out. But considering the age of these machines, you probably would be better off just sliding them into a dumpster!

AFter putting a Power Mac 6500 motherboard (250 MHz) into a 5200 shell, but just when I thought I was done, the 5200's fan started making an awful grinding and dying vacuum cleaner sound. So I thought I'd replace it. That's when the problems began! The interior of a 5200 resembles somewhat of a medieval fortress:

It is possible to sneak that fan out of there without complete disassembly. The first step is to remove the back metal piece by removing the four screws indicated:

Once this plate is removed, you are going to have to remove screws holding the analog board in place. The analog board is the circuit board on the right hand side in the picture above. There are three obvious screws to remove - two on the side, one on the back of the computer (keep the one on the back separate, it is a different screw type). Once you have these removed, you will be able to lift the board slightly and lay it down sideways. This may be facilitated by unclipping one cable as indicated in the photo:

Good news! This is all the room you will need to slip the fan out. If you look straight down into the machine, you will see a single screw holding the fan housing in place. Remove it with a magnetic screw driver so you don't lose the screw:

Now you should be able to slide the fan and it's housing out on the analog board side. Two small tabs on the fan housing hold it in place, so you'll have to push it in a bit before it will come out. There's only one thing you must do first - disconnect the fan from the power supply board - you can't miss it, it's at the very corner of the board (disengage carefully, lift the tab on the back of the connector):

Pulling the cord out from the others it is entangled with is a hassle, but it can be done! Now you can pull out the fan and housing:

The rest is easy! The fan is held in by only two screws - take them out, replace the fan, and reverse your steps. It is a 92 mm fan - if you are purchasing one, I highly recommend the Silencer fans from PC Power and Cooling.

But being Canadian, I kick myself for having ordered only ONE of these fans that I used in my G3AIO, and the shipping costs are a killer. So I decided to adapt the housing to a smaller, quieter fan I had laying around. Because the 6500 motherboard has its own processor cooling fan, the big fan in the housing is likely overkill anyway. Here are my steps if you want to try such a nerdy modification (there's probably an easier way, but what the heck!):

1. Clip off the useless fan cover:

2. Remove the screw holders from the fan housing:

3. I chose a significantly smaller fan!

4. If you choose a smaller fan, you need to cut a piece of sheet metal that fits in the fan housing:

5. Before you attach it, trace the fan in the centre of the sheet metal.

6. Cut a hole in the centre that matches the fan diameter, then attach the sheet metal to the fan housing:

7. Drill two 5/16 holes for the screw holders.

8. Attach the fan with the screws (you didn't lose them, did you?)

9. I added some foam to the gaps in the other side to further dampen sound and vibration:

That's it, it's Miller time! Now just put it back into place and you are done. I measured the temperature near the processor before and after with a temperature probe, and couldn't detect a difference. The end result is a Power Mac 6500 250 MHz machine in a Power Mac 5200 shell, that is nice and quiet!