Amiga 1200 Power Supply Made From An Old ATX Power Supply

I was having some issues with my A1200 constantly crashing and resetting, and at the time I had been using an old, original white power supply box. A friend of mine had suggested that I get a new one, as the caps might be going bad in it. It would certainly explain the resets at random occasions and a few other things, so rather than buy a new one, I decided to convert an old ATX power supply I had laying around and make use of it.

As with all things power related, if you plan on trying to make one of these things at home, make sure it is unplugged and de-energized! I will not be held responsible for anyone electrocuting themselves!

So, what do we need to get going?

• An old ATX power supply, any size will do. I used an old 250watt supply.
• An old Amiga Power Supply or Power Connector
• Multimeter
• On/Off switch. I was creative and re-used one (See Below)
• Crimp Tool/Insulation Tape

Step 1 – Prepare the Power Connector

Before we can start, we need to be able to connect the power to the Amiga. The best way to do this is to acquire one from an old Amiga supply. Most Amiga fans have several laying around, I used one from an old supply I had brought over from England years ago. It’s not much use to me here in the USA anyways 🙂

Open up the power supply, and cut out the wire at the base of the transformer. This will give you the maximum amount of length available on the new project. You can of course cut it down if you want a shorter one. My current desk doesn’t have a very good power layout, so having a 6 foot cord worked out quite well.

Step 2 – Acquire A Power Switch

Due to the ATX power supply needing a short to work, the best and easiest way to regulate this is to use a simple power switch. Being creative, I used the one that was already in my existing Amiga PSU and cut it out with a length of wire. It also helps to keep it a little more nostalgic!

Step 3 – Prepare the ATX Power Supply

The easiest way to make this work is to cut off one of the Molex connectors on the line that powers a HD. Most ATX supplies have some that are longer than the rest, just cut the plug off the end. You also need to cut the Blue line from the ATX Motherboard connector (-12V). Make sure to clean the other end up, so theres no exposed wiring hanging around. In the next step, there is a table showing the common colour codes for the Amiga wiring.

Step 4 – Assemble The Wires Together

Theres a number of different ways to connect the wiring, some people prefer to just twist wires together and tape them, but you can also use a crimping tool, or a terminal block. The good thing with terminal blocks during the testing phases is that you can swap the wires around if you do manage to get them mixed up. Below is a table showing the common wiring colours of the Amiga to ATX connections. Some Commodore wires may vary in colour, if this is the case, see below to determine how to make sure you have the right ones. It is crucial that it be correct before it is plugged into your Amiga. Don’t blow it up!

Assemble/Connect the wires as shown in the table. Make sure they are safe from coming into contact with each other.

Step 5 – Connect The Power Switch

Now we need to connect the power plug to the ATX supply. On a normal motherboard, this is done by shorting out 2 pins together. This is why using a switch makes the job perfect. The simple way to acheive this is to look at the blue wire we cut off the motherboard connector. The pins to short are directly next to it (See the picture above) in the form of the Green & Black wires.

Cut these wires and follow them up to the power supply, you can then attach the switch directly to these Green & Black wires and voila! You now have a working switch. When the switch is on, the power supply will work, and then flick the switch to turn it off again. Remember, not all ATX power supplies have a power switch in the back of them, so this is a perfect solution to the problem.

Step 6 – Test The Crap Out Of Your Wiring!

I can’t stress enough that you DO NOT plug this new power supply into your Amiga until you have FULLY tested that it’s wired up correctly. If even one wire is not correct, your Amiga would be toast. Take the time to test your work, before plugging it in! All you need is a simple multimeter to read the voltages.

I drew a quick diagram of how to read the values. When you are holding the ATX side of the power plug and looking directly at the pins, each one should measure exactly as they are pictured in the diagram. Place the Negative electrode on the outer shield of the connector, and touch the Positive electrode on each of the pins. You should get very close to the values shown. If a wire is in the wrong location, then you need to fix it and test it again. It’s extra-important to test this when your Amiga wires don’t match the colour table above.

Step 7 – Give it a whirl!

When you are confident your wiring is all good, you can give it a try in your Amiga! She should boot up just the same as before, so take note if any wierd behaviour occurs. In my case, my A1200 booted a lot quicker and almost all my crashes and random resets stopped happening. It wasn’t until I did this, I realized how bad my original power supply really was!

If you have any questions about this, feel free to ask them in the comments. I hope you find this useful!

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