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iMac G4 Makeover
Enclosure Construction
An Open Source Hardware/Firmware/Software Project

Overview
The project: squeeze a new square motherboard into a round hole.

Starting with an old 800 MHz 15 inch iMac we are going to fit a new(ish) fast(ish) motherboard. All is relative. You can find motherboards here.
Please don't destroy a perfectly good iMac, there are plenty of dead ones around.

Below are the struggles with the first two iMacs as I'm attempting to fit a couple of micro-ATX motherboards into a box that is just slightly too small...

Modifying The Base

This is the version with DVI graphics card.		(Click thumbnail)
CPU (logic board) is already out. Nearly there. Strip the base down to the bare metal, more than this picture. Carefully remove theIEC 320 power connector and save all screws. Remove the antenna and the plastic cover.
The new motherboard is too long so we need a back porch. You need a decent bandsaw for this step. All we're going to do is saw out around the existing hole and extend that cutout to the rear edge. Mark first and then saw this in one cut each side so that you save the centre cutout material in one piece. The cutout should be about nnn wide. Drawing here.
The cutout doesn't have to be exact (see my wobbly saw lines) because we're going to glue it on top of the basement walls. Did I mention that the new motherboard with low-profile PCI graphics card is still too tall? That's right, some of it has to go downstairs. Even if you are using a motherboard with DVI I suggest a basement box. It allows for a larger CPU fan and also a PCI card.
The crude basement box in all its glory. The sides are 1/2" by 3/4" wood glued onto 1/8" thick hardboard. If you live in metricland I'm sure you can find something that works. Drawing here.
Here's a top view of the base on top of the basement box.
And here it is from underneath.
The box is held in with three wood screws, and here the new Foxconn Atom motherboard is in the basement.
Now to see if the inner metal dome fits with the new motherboard in place. As you see, I was very generous, both with the depth of the basement and the height of the cutout. If you are using a DVI motherboard the basement can be shallower and the cutout smaller.
The notch in the plastic cover is to clear the graphics card and again will not necessary with a DVI motherboard. The DVI connector still has to have the iMac video adapter fitted, but first I'm going to look at wiring directly to the graphics card.
Closeup showing the motherboard connectors. Somehow those ugly connectors have to be boxed in. The next major puzzle is locating the mickey mouse AC input connector.

Model

		(Click thumbnail)
The enclosure was drawn before dusting off the saw. The old proverb: 'Measure twice, cut once' is now 'Draw as a 3D solid once, cut once'. The graphics card is in orange and the purple cube is the CPU, heatsink and fan of the D201GLY. STEP is available here.
Bottom view of the model.

Modify Dome
Description here as the prototype is built.

Documentation
BOM (Bill of Materials) is available as a Google Docs Spreadsheet here.