This article will detail the steps for building an external power supply for an early model Atari 520ST. There are ways to improve this build with better connectors, and I plan to design and print a 3D printed case for the final product in a future revision. Cases for Amiga power supplies that use similar builds are available on Thingiverse - but unlike the Amiga, the Atari ST doesn't require a power switch on the PSU. I plan to omit the switch on my 3D print design.



Materials Required

• Mean Well RT-65B AC-DC Power Supply Triple Output 5V 12V 8 Amp
• UL2464 Four Conductor Power Cable (I used 22AWG but I might use 18AWG if I did this again)
• 7-Pin DIN Female Audio / Video Adapter (this one from Amazon should work, but I used this metal connector from Show Me Cables in the tutorial... it's kind of junky)
• A C13 or C14 PC Power Cable (everyone has piles of these around the house like me, right?)

Tools Required

• Multimeter
• Soldering Iron, Solder, and Flux
• Cable Strippers
• Heat Shink Tubing or some hot glue

Build

Step One



Cut the female end from your C13/C14 cable. Expose the three wires and tin (better than I did, ideally).

Step Two



Attach your wires as follows (left to right):

1. Black to L (Live)
2. White to N (Neutral)
3. Green to Symbol (Ground)

Step Three



Plug the power supply in and verify your voltages.

• +5V should be +5V
• +V2 should be +12V
• V3 should be -12V

Step Five



Cut the four conductor cable to length (I cut it to be as long as the C13/C14 side). Cut and strip both ends, the conductor wires, and tin.

For the purposes of this tutorial we will assign the colors as follows:

• Yellow is +5V
• Red is +12V
• White is -12V
• Black is COM

Step Six



Consult the diagram above When you start to solder wires to the DIN connector, remember that the diagram is oriented as though you are facing the back of the computer, not the front of the DIN connector. Remember to add your heat shrink tubing before you begin to solder.

Step Seven



Bridge the two +5VDC pins with the yellow wire and solder into place.

Step Eight



Bridge the two Ground pins with the black wire and solder into place

Step Nine

Solder Red to +12VDC

Step Ten

Solder White to -12VDC

Step Eleven



Attach the other end of the cable's conductors to the Power Supply as follows (Left to Right):

• V3 = White (-12V)
• +V2 = Red (+12V)
• +COM = Black (Ground)
• +5V = Yellow (+5V)

Step Twelve

Plug in your power supply and test voltage at the DIN connector to ensure you have continuity and the correct voltage on each pin.

Step Thirteen

Heat your heat shrink or coat the back of your DIN connector in hot glue if you're a savage :) (I suppose a savage wouldn't bother with either... if you are a gentle savage use hot glue)

Step Fourteen



Assemble the DIN connector

Step Fifteen



Test!

Gotta say, i really love the RT-65B - i made a bench supply for testing SE & SE30 logic boards, using one of those. Still keep meaning to get another one to shove into the original Amiga power brick.

>> Kai Robinson said:

Gotta say, i really love the RT-65B - i made a bench supply for testing SE & SE30 logic boards, using one of those. Still keep meaning to get another one to shove into the original Amiga power brick. Click to expand...

They really are robust and versatile. I know there are some Cisco switch power supplies out there that offer the same features but sometimes being able to hit Amazon and just say "add to cart" is worth the trouble.

I made a similar one from an ATX power supply a few years back, but I couldn't find a good DIN connector at the time, sorta had to jury rig something that fit... good to know that they're maybe easier to source now.

DOS Fox told me that the Cisco 34-0874-01 power brick is another candidate for making an Atari 520ST power supply. Might be good to keep in mind if you have friends in IT, or if you have access to a cheap source.

It's rated for 3A @ 5V, 2A @ 12V, 0.2A @ -12V, and a maximum of 30W. This is higher than the original 520ST power adapter's specifications.