Amiga 4000 SFX Adapter

SFX form factor power supplies are a good replacement for the original Amiga 4000 Desktop PSU, because they fit well into the same space. This printable is a frame that fills out the empty space below the PSU, gives room for ventilation, and also offers brackets for using cable ties for cable management.

I was inspired by the Amiga 4000 Small Form Factor Power Supply adapter by delsydsoftware, but there I was missing the cable management. Also, without the lock clips, the Amiga can be accidentally turned on by pushing the adapter from the back. So I created a new frame from scratch.

Find some more details in my blog article about the Amiga 4000 refurbishment.

Printing

Print the main part, and two of the clips.

Do not use supports, as they may obstruct the cable tie tunnels. Besides that, there is nothing special to observe.

If you can print in different colors, you can use the adapter-white and adapter-red files to add a colored Amiga logo to the frame. If you leave them out, you will get an embossed Amiga logo, which looks nice as well.

Assembling

After printing, mount the power switch to the appropriate place. Slide the adapter into the mounting brackets at the bottom of the Amiga case, and use the two clips to fix the adapter in place. The flat side of the clip is oriented toward the metal bracket. They snap in like press-studs with a bit of force, no glue is required. When wiring, use cable ties and the printed "tunnels" to fix the wires to the adapter.

About the PSU

I pixeled out the PSU labels on the photos intentionally because that PSU turned out not to be suitable for the Amiga. It has a “hybrid fan control” that completely turns off the fan on small loads (the Amiga 4000 actually is a small load for today's standards), leaving the rest of the Amiga system uncooled.

In general, I don't want to recommend a specific PSU model for the Amiga 4000, as I don't want to be liable for the damage that it might cause in long terms. The safest option is to have the original “Skynet” PSU overhauled by a trained technician, and then use that one, as it was specially designed for the Amiga 4000.

If you choose a PSU for your Amiga, you should make sure…

• that the fan is permanently active. The PSU is the only component in an Amiga 4000 Desktop that provides ventilation. If the PSU fan is turned off, other components may overheat. Make sure that there is always sufficient ventilation, especially if you use mechanical harddisks or 68040 CPU boards.
• that the individual voltage rails deliver sufficient power. An Amiga has the most load on the 5V rail, while modern computers have the most load on the 12V rail. The 5V rail should deliver at least 18A.
• that the specified minimum load is met on all power rails. The Amiga makes no use of the 5Vstby and 3.3V rails, and the load on the 12V and -12V rails are neglectible. Too little load can cause stress to some PSUs. A good PSU should generate the other voltages from the 12V line by DC/DC converters. An optimal PSU should have a minimum load of 0A on all lines.
• that you buy a PSU from a renowned brand, not a cheap “no-name” product. Better invest a few more bucks for a really good PSU, than killing your Amiga with a cheap one.

You do this modification at your own risk.

Do not attempt to open a PSU, as it may contain hazardous voltages even hours after being disconnected from mains.