Power Supply Unit for Atari ST/E and MegaST

A solderless drop-in PSU kit for your Atari ST, STE or Mega ST

The SidecarTridge Mean Well PSU Kit drops a modern, industrial-grade power supply into the bay where your tired original PSU lives. It pairs the well-known Mean Well RPD-60A open-frame PSU with a custom riser PCB, the right harnesses and the mounting hardware to fit the original ST, STE and Mega ST chassis. No soldering, no chassis modifications, and one less reason for your machine, your peripherals and your SidecarTridge boards to die a slow death by sagging rails.

Over time the capacitors and components inside the original PSU deteriorate with age and use. That leads to unstable voltage, erratic behaviour and, in the worst case, electrical shorts that can damage the motherboard. A tired PSU is also a leading cause of SidecarTridge device failures. A modern, stable power source protects the motherboard and every board plugged into it.

Ships from Spain. For the Atari ST, STE and Mega ST.

Key features

• Solderless installation: plug-in harnesses replace the original PSU connectors. No soldering on the motherboard, no chassis modifications, no permanent changes.
• Industrial Mean Well RPD-60A: built around the medical and industrial-grade Mean Well RPD-60A, with clean and stable +5V, +12V and -12V rails sized for the Atari ST family.
• Custom riser PCB: a dedicated riser board mounts the Mean Well unit in the original PSU bay, lined up with the existing case posts. No glue, no zip ties, no improvisation.
• 100-240V auto-range input: universal AC input on both sides of the pond. The PSU detects 110V or 220V automatically, no jumpers, no manual switching.
• Complete harness in the box: motherboard harness with the right JST and TE connectors, AC input cable and Speak-on terminal block. Everything you need to wire the new PSU end to end.
• Fits the original PSU bay: designed for the Atari ST, STE and Mega ST original PSU footprint. No bent metal, no plastic surgery on the case.

Kit contents

• Riser PCB for the Mean Well RPD-60A, with mounting holes that line up with the original PSU bay.
• Mean Well RPD-60A open-frame PSU, 100-240V AC input, +5V / +12V / -12V output. Shipped from our stock in its original packaging.
• Motherboard harness: JST VH3.96 6-pin to TE 171822-6 6-pin, 10 cm.
• AC input harness: JST VH3.96 3-pin (2 pins wired), 10 cm.
• Speak-on 2-pin terminal block for the AC connection.
• 8x Philips M3 4 mm screws for the riser and PSU.
• 4x M3 nuts and 4x M3 washers for the PSU mounting.

Installation overview

1. Unplug the Atari from the wall and open the case.
2. Unscrew the metal RF shield to reach the PSU. On the ST and STE only the PSU portion needs to come off; on the Mega ST the full shield is removed. The shield goes back on at the end, so the machine ends up stock.
3. Remove the original PSU and keep the screws, you will reuse the bay.
4. Mount the Mean Well RPD-60A on the riser PCB with the provided M3 hardware, then bolt the assembly into the original PSU bay.
5. Wire the motherboard harness between the new PSU and the existing motherboard connector, and wire the AC input through the Speak-on terminal block.
6. Double-check the AC wiring, close the case, and power on.

Step-by-step photos and tips live in the PSU quickstart guide and the SidecarTridge PSU documentation.

Compatibility

The Atari 520ST short uses an external power brick that this kit is not designed to replace. If that is your machine, the External USB-C PD PSU is the right product.

Specs

• Weight: 220 g.
• Dimensions: 100 x 100 x 50 mm.
• AC input: 100-240V AC, 50/60 Hz, auto-range.
• DC output: +5V, +12V, -12V.
• Motherboard connector: JST VH3.96 6-pin to TE 171822-6 6-pin harness, 10 cm.
• AC connector: 2-pin Speak-on terminal block.
• PSU datasheet: Mean Well RPD-60A.

Frequently asked questions

Does it work on 110V mains in North America?
Yes. The Mean Well RPD-60A is a universal-input PSU and accepts anything between 100V and 240V AC at 50/60 Hz. No jumper, no switch, no firmware setting.

Which Atari models are supported?
Atari ST (520ST internal, 1040 STF, STFM), STE and Mega ST are all supported. Mega STE, Falcon and the 520ST external power brick are not. TT has not been tested.

Can I use this kit on the Atari 520ST short with the external brick?
No. The 520ST short was sold with an external power brick instead of an internal PSU. For that machine, the right product is the External USB-C PD PSU, a direct replacement for the original external brick.

How hard is it to open the Atari ST and swap the PSU?
The case is held by a handful of screws and the metal RF shield comes off with another few. With basic hand tools, attention to the AC wiring and about 30 minutes of patience, this is a perfectly approachable job for a hobbyist.

Do I need to solder anything?
No. The motherboard side is plug-and-play through the supplied harness. The AC side is wired into the Speak-on terminal block, which is a screw-down connector, not a soldered joint.

Can the PSU harm my computer?
Once correctly wired and seated, the Mean Well RPD-60A delivers rails well inside the Atari ST family's specs, and is safer than a 40-year-old original PSU running on dried-out capacitors. The risk is in the AC wiring on your side: if you leave a Speak-on screw half-tight, you can harm yourself or the machine. Follow the quickstart and double-check the AC connections before powering on.

Is this product for me?
Yes, if you enjoy tinkering with your Atari ST family, you are comfortable opening the case and you are happy to wire an AC mains input. This is a homebrew product built for hobbyists who want a long-lived, industrial-grade replacement for their original PSU. It is not a sealed appliance, and it is not the right pick if you want a fully external, low-voltage-only solution.