Introduction: G4 IMac to Black Mac

By
About: Doing a lot of stuff with computers right now.

Started project with a relatively faulty old iMac G4. DIdn't boot, but the power supply tested OK. Faults appeared to be with the motherboard and the display.

Goal is to make a workable iMac G4 with a modern OS - not too fussed about whether or not it is MacOS since I already have a Mac or two on my desk.

End result is a relatively modern iMac running Linux with a reasonably good matching 22" display.

Lots of inspiration from Dremel Junkie and Macaron

Supplies

Step 1: Rip It to Bits

Both Dremel Junkie and Macaron provide really good help on disassembly. I also made use of iFixIT.

I ended up not using much of the insides. Motherboard, drives, fan etc were all disposed of. The arm needs to be removed and the farraday cage. I painted all the plastic separately and then put it all back together. The power supply in my case I left, but if removed creates plenty of space. Either way to paint it needs to be pulled out.

The arm needs removing from both the monitor and the base first. The monitor can be tricky and different models have different methods so I recommend doing some reading and watch some YouTube before trying. I replaced the monitor which was faulty so I'm not full of advice on how to do this carefully.

Step 2: Setup NUC in Base and Painting

I used a piece of 4mm clear acrylic to cover most of the base where the motherboard had been. This was cut out with a jigsaw on a slow speed and then drilled to match the existing holes.

Some threaded inserts were used to help mount the NUC and other boards. I didn't pull the NUC apart too much - just removed the top case and then mounted onto the acrylic base.

Various extension cables were needed to replace the ports on the back - mostly just glued into the previous holes. A little 3D printing of some extra plates to make them look a bit better.

Early on I completely disassembled and separately painted all the main components with a matte black spray paint. I used a specialty primer+paint product that is intended for use on plastic. It worked extremely well and in general three coats was what was needed. The silver apple logo could be removed easily and was glued back on after painting.

Step 3: The Monitor

The iMac G4 arm is tricky. The Dremel Junkie guides in the link at the top are super helpful if you want to keep the same cables. I had a bit of a play with this but it was beyond my skills/patience. Macaron had some useful tips on opening the arm in his video. He used a HDMI ribbon cable from the LCD through the arm. I tried this (twice) but I damaged the ribbon cable each time.

I settled on:

  • 2 x wires (18 gauge) for 12V power
  • Standard twisted pair CAT 6

It's a tight fit - but these three cables will fit through. I was going to go find a slightly thinner cat5 cable but it was ultimately doable.

These arms are a complete pain, however it is manageable with a few bits of help:

  • I used 2 x needle nose pliers to unscrew the odd screws used to hold the arm together (this also comes in handy for the Apple Pro Speakers)
  • I couldn't stop them falling apart and they are devils to put back together (I gave up trying to stop this and just let it come apart).
  • To stick back together hook up one end and then insert a screwdriver in the other hole to leverage it back onto the spring. It's really really difficult but doable.

Providing the monitor can be converted to 12v this then allows HDMI via the RJ45 cable and the cables can be fed through into the back of the monitor (obviously means drilling a hole).

Converting Monitor to 12v

  • On the back of the LCD panel look for the model name. Search this on Aliexpress. With luck you can find a generic LCD driver board that will accept 12V DC. For example mine was M215HTN01. Plenty of options. If you can't find something try a different monitor. See the example picture of my driver board. This is typical - they come with the digital board, an invertor and a button board.
  • I cheated slightly and mounted the buttons on the back of the monitor under the cable cover. If I was more ambitious I might have tried to solder some wires up to connect them to the original buttons on the front.
  • The Ethernet cable can be used with a set of Ethernet->HDMI convertors. I used some slightly more expensive powered versions so needed to get 5V on both ends to do this.
  • Messy, but as it is it's all hidden inside the monitor it looks pretty slick.
  • You could avoid most of this if you are OK with a normal power cord hanging out the monitor, even more of it if also using an external display cable.

Attaching the Monitor

This was fairly simple. I used the stand VESA adaptor the monitor came with. Taking off the stand left a round gap to fill which was done with a 3D printed part with the right sized hole for the iMac arm. This lets the monitor screw in pretty easily. The real problem is just plugging it all in. Basically I needed to assemble the monitor onto the arm in reverse.

I used a pretty generic Dell 22" LCD. Since it's a lot newer than the original it was still a good weight compared to the original so despite the size it still works fine on the arm.

Step 4: Power

I was using the original PSU but this still left some power problems.

The power supply needs to feed:

  • The Intel NUC (12V)
  • The monitor (12V)
  • The fan (12V) via the fan controller
  • The amplifier (12V)

This is all good - but ideally I only want the monitor, the fan and the amp to have power while the computer is on.

To solve this - I used a 4 channel relay controlled by the 5V header pin on the board of the NUC. This means power is cut to the monitor, fan and amp when the computer is off - or if it goes to sleep. This is pretty simple - a 5V signal from the computer is used to switch on the relay.

Additionally I didn't want the fan running all the time and the NUC doesn't have any easy method for controlling fan behaviour. My assumption is the whole unit could probably manage without much cooling assistance anyway - convection should probably keep airflow working well. I used a small 12V fan controller board with temperature probe. This helps have the fan only run when required.

Step 5: Apple Pro Speakers

These are non-powered 10W speakers. To get them working an amplifier is required. They come with a proprietary 2.5mm jack. I decided on a big overhaul:

  • I completely disassembled and painted the enclosures in the same matte black paint
  • Desoldered the original cables and replaced with a standard black RCA cable set
  • 3D printed a cover for the surround of the speaker (also painted)

Female RCA ports connected to the amp were set as one of the ports on the back of the iMac.

The amp is probably over powered - volume needs to be kept to no more than 20%. Pretty sure it wouldn't be hard to blow these speakers out. I'm trying hard not to find out.

A useful blog to help with understanding and fixing these speakers.

Step 6: Finished Setup

The system has Ubuntu installed.

Front Ports (inside CD-ROM cover)

  • USB-C (really just for charging)
  • USB3
  • MicroSD/SD/CF reader

Rear Ports

  • 2 x USB3
  • Mini Display Port
  • 2 x RCA (powered amplifier)
  • Ethernet (Gigabit)
  • 3 x Audio Ports

Inside

  • Intel NUC 5i5RYH (8GB, 256GB SSD)
  • 30w stereo amplifier
  • USB sound card (3 ports)
  • 4 port USB3 Hub
  • 4 channel relay for power cut off
  • Temperature control board for fan

Outside

  • Dell 22inch monitor
  • Microsoft keyboard and mouse set
  • Reworked Apple Pro Speakers