millerjs.org

A couple of weeks ago I found a very reasonably priced iMac G4 being sold locally, and having always been somewhat interested in them (and having never had one before) I decided to get in touch with the seller and go pick it up. What I ended up getting was a fantastic condition first generation iMac G4/800. It has a few minor scuffs and marks on it here and there, but nothing a couple of alcohol wipes couldn't take care of.

What has kept me away from iMac G4s in the past has been the fact that, by and large, they are OS X only machines. I have very little interest in PPC OS X as it largely still feels too new to be "retro" and yet is too slow and incompatible to be used for much. I tinker with it from time to time, but System 7 and Mac OS 8 and 9 are where most of my interest lies. Only the first revision of the first generation of iMac G4 could run 9, and even then only it's special version of 9.2.2 (which is not hard to find), but that is good enough for me. I decided to take a gamble on this particular machine because 1) it was very cheap, 2) it looked to be in good condition, and 3) it was a 15", and all of the first gen iMac G4s were 15", so there was a chance that this one was a first gen. Reading the service manual I also learned that not only is the first gen the only generation to be able to boot natively into 9, but only machines with serial numbers less than xx305xxxxxx will as well. This machine is in the xx200 range, so it should boot 9 just fine. It's also the highest end first generation model sold - with the 800MHz CPU, 60GB HDD, and Superdrive. It was also factory upgraded to 512MB with a single PC133 DIMM, leaving the SO-DIMM slot vacant. The airport slot is also surprisingly empty, but that's not really a problem for me as I have little interest in WEP encrypted 802.11b.

Now, the bad news. Unfortunately this particular machine has screen issues. Particularly, the "white screen of death" that seems to be not entirely uncommon when researching these machines. This one in particular boots as one would normally expect when the power button is pressed - it chmes, the fan spins up, if an HDD or CD with OS loaded is present you can hear it begin to boot - but the screen is forever white. When it first kicks on the screen is more of a gray, in fact it's the same gray that you would expect for a machine of this era's first image (all of my G4s do it too) but instead of showing a happy mac, or the "OS not found" symbols, within a few seconds it transitions to a bright white. One way I know that the machine is booting is that I am able to enter open firmware and use commands to shut down, reboot, and eject the optical drive tray. This is good news, as it tells me that the motherboard works properly, and when I hear it booting from the HDD or optical drive I know that the IDE bus works as well.

I don't know which part is causing the problem, but I have been able to narrow it down to one of three things: the video connector on the motherboard (very unlikely), the video cable that runs from the board, up the neck, into the screen (somewhat likely, but I would expect flickering when the screen is articulated and wiggled), or it's the LCD panel itself - most likely, I believe, and frankly also probably the easiest to replace. The second easiest would be the logic board, but the video cable is contained within the neck itself, and getting a new neck with wiring harness so far seems rather difficult. I would also like to avoid replacing the logic board because there is little certainty that I would get another 800MHz first-gen board, which is what I very specifically want.

Now, this machine does actually have video output. It's one of the few macs (along with a handful of iBooks, PowerBooks, and other iMac G4s and G5s) from the early 2000s to use "Mini VGA" which, aside from having a weird connector, is exactly what it sounds like. On this machine it doesn't allow for adding a second extended display - it can only mirror the primary display - but in this case that happens to be exactly what I want to do. Enough macs used Mini VGA that there are a plethora of the adapters available, and I was able to pick one up for about $4 shipped. So you may be able to see where I'm going here.

What I have chosen to do is remove the neck and screen assembly entirely, and what remains is what I have chosen to name "The Dome". The Dome is, obviously, the bottom half of an iMac G4 - a white plastic hemisphere driving an external monitor. It looks a bit strange, sure, like a mac mini about to pop, but it is a more compact G4 running OS9 than either the Quicksilver or Digital Audio, so that's a plus. And at 800MHz with 512MB RAM, it's no slouch either. Granted the GPU is fixed (GeForce2 with 32MB) but seeing as it's only ever driving 1024x768, that's not really an issue. No potential for a SATA card either, but I plan to at least get it upgraded with a 7.2k hard drive - the original superdrive will stay.

The process for removing the neck and screen is fairly trivial. Remove the bottom case, disconnect all the wires, and set it aside. Remove the drive carrier, power supply, and fan from the upper housing. The hardest part is removing the extraneous wires from the blind mate connector. This connector carriers a number of signals - power/sleep LED, microphone, display inverter voltages, fan, and speaker. Everything but the fan and speaker is in the display, so I removed those pins from the connector. The fan could be powered from the drives' molex connectors, and you could forgo a speaker, but I didn't want to do either. I also took this opportunity to clean out the fan and top of the case, as well as the peculiar two-part power supply. The neck is secured to the base with five screws, and once they are removed it pops straight off, and the various wires are fed through the hole left behind. I may 3D print something to cap this hole, but for the time being I am going to leave it as is.

As mentioned earlier, I do plan to upgrade the hard drive to a 7200RPM unit. The costs of PC133 SODIMMs are also so low right now that, at $8 shipped, there's really no good reason to not upgrade it to 1GB RAM. The fan is a standard 92mm PWM unit, so I plan to upgrade that to a Noctua as well. There's no real need for this - the included fan works just fine - but I would like something with greater airflow at lower speed. I would also like to find something that allows me to monitor the temperature and fan speed in OS9, though I don't know that such a utility exists. I have also noticed, in a couple of days of using it, that it is far more stable than my Digital Audio. This will require some further followup and investigation, and perhaps a future post.