My iMac 233's video had failed with lots of fizzing and crackling. I expect it was the flyback transformer. I wasn't that keen on getting it fixed — I was much more keen on having a bit of fun resurrecting it into an iMac with a difference.

The symptoms of a possible candidate
When you power on the iMac, it powers up for a few seconds, the LED glows orange and it immediately powers down again.

To check if the unit is suitable for 'conversion' and not totally bust, take off the bottom case cover and disconnect the internal monitor cable. Power it up again. If it seems to power up normally instead of reacting as before, it's a suitable candidate. If you like, at this point you can power down, fit a Mac screen to the video connector (or a PC screen with suitable adapter), and power up again to see the iMac back in action. Have a look in the Monitors Control Panel and be pleasantly surprised at the expanded video capability!

In which case?
After considering various options including a homemade case to contain the motherboard I decided the most practical option was to recase the electronics in an old PC case. The one I used was a desktop-style case from an old 386. I removed its power supply; it's not suitable for an iMac anyway, and that location was spot-on for the iMac motherboard.

Click these pictures for a larger version. The numbered items will be clearer then. If you have any questions email me and I'll do my best to help. I'll document the disassembly of the original iMac if enough folks ask as I need to repeat this project shortly with another iMac.

Disclaimer: this operation will indeed invalidate your warranty and anything you undertake is at your own risk!

Guy Hemmings

The Drives
(1) In the iMac, the IDE bus normally supports the hard drive through the standard connector and the CDROM drive through the special slim connector. Rather than have to try and deal with the slim CD connector I got a standard three-connector IDE cable, fitted an Apple CD drive set to use as 'slave', set the hard drive as 'master' and set one above the other in the PC drive bay. This would be an ideal opportunity to fit a CDRW instead of the standard CD drive. I'll probably do that later on.

The Motherboard
(2) The iMac's motherboard is fitted upside-down (ensure you are happy with the amount of fitted memory first), and is set on two pillars giving enough clearance above the PC powersupply platform; if you can do, fit a third to give better stability. I fitted a PC processor cooling fan on the underside of the platform blowing cooling air onto the iMac's processor. In the original configuration it would have got quite a draught (draft) from the iMac's fan, and I felt it could overheat in this location. The plan for more cooling is to fit the iMac's original fan across the empty expansion card area, to blow across the iMac power supply board.

I unwound all the grey tape from the cable (3) between the motherboard and the power supply to make it more flexible. It is able to reach across the case far enough to be able to have the power supply board orientation ideal for the power cable entry (6). I rubber-mounted the power supply board with thick self-adhesive pads to allow good clearance, and added an extra earthing cable from it to the case metal.

Here you can see the drive arrangement. The iMac's motherboard just fits in neatly enough to allow the drive connectors not to interfere with it. The PC processor fan tucked in underneath is powered from a double-headed power connector fitted to the hard drive.

The orientation of the motherboard is ideal in that it allows all the ports to show out the back (needs to be covered by some kind of a tidy panel), through the hole normally occupied by the fan outlet of the PC's power supply. Ensure your mounting is steady enough to allow connection to the ports without distorting the motherboard. The modem is rather delicate in this respect, it doesn't have 'any visible means of support' and could do with some reinforcement. I'm not using the modem, as I use the network for internet access. I think you will find that the iMac will not pass the POST (power-on self test) if you remove the modem and therefore not start up at all; so leave it in place.

I just used self-adhesive pads to fix the speakers to the inside of the case. They work fine. I skipped refitting the microphone though.

The PC's reset switch has become the iMac's power-on switch; as the iMac uses soft power, it can use the momentary-action reset switch as a substitute. The switch was simply wired across the iMac's power button's connection. The small circuit board can be tucked away somewhere convenient.

I was fortunate enough to have a short adapter cable (see '5' in top photo) which has the Mac 15-pin video connector on one end and a 15-pin VGA connector on the other; which was ideal for having a video connector fitted into one of the expansion slots. I took apart an old PC video card, and fitted the VGA connector to its steel end bracket, to give a good stable connection for fitting the screen. Talking about the screen, an added bonus of recasing the iMac is that the VRAM can support up to 1600 x 1200 pixels, which means you can now work on a 21" screen if you like!

I mounted the small video board (that in the iMac lives behind the drives) to the case with a metal bracket. I think if you had to you could chop the redundant end section off this board, but I had the space and didn't bother.

The finished result works just fine. I just need to locate a blanking plate to cover up that floppy drive space. If you are feeling really adventurous, you can even fit a floppy drive connector to the motherboard, and connect up a Superdrive. On the original 233 motherboard there is an unused location for the 20-pin floppy connector, so you could finish off the illusion completely.

I fitted the processor from a 333Mhz iMac to give some extra oomph, and now I'll load OSX...

March 31: It appears that there are different configurations of the power supply board. For identifying which one was used here: the power supply connector on the PSU board for connection to the motherboard, has a single black connector, rather than twin white connectors (see (8) here). If I get any useful info on success or otherwise with other configurations I'll report back. Guy.

April 1: I'm getting a bit of interesting feedback, so I've set up a forum for chat about the resurrection project here so thatfolks can share their experiences.