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15 June, 2024
Sega Neptune

Reviving the Canceled Sega Neptune


The Sega Genesis was an absolute hit throughout the 1990s, drawing in gamers with its colorful 16-bit graphics and incredibly speedy gameplay. Cashing in on the success, Sega was quick to create hardware add-ons like the Sega 32X, as well as combo consoles like the Sega CD. In 1995, Sega announced the Neptune, a console that combined the strength of the Genesis and 32X into one ultra-powerful console. Unfortunately, the project was canceled, and never saw the light of day… until now.

Reviving the Canceled Sega Neptune Console

Today, I’m tackling the task of restoring Sega’s dream combo console by creating my very own Sega Neptune. Now, I’m hardly the first to accomplish this task, as talented modders like Longhorn Engineer and infidelty_nes have been making Neptune builds for years. However, thanks to the Neptune replica shell created by Dan (aka DVIZIX) and PCBAssembly99, we can craft a console that looks exactly like Sega had envisioned it.

If you want to build a Neptune yourself, you’ll need several parts, including a Model 2 Sega Genesis (VA3 or VA4 preferably) and a 32X donor console. You’ll also need a triple bypass board, a 90-degree cartridge slot, four extended ribbon cables, and a terminated cable to power the 32X internally. Additional rubber standoffs and machine screws are also needed for tidy internal management. Of course, you will also want to pick up the Sega Neptune replica shell, which can be customized to your preference.

Sega Neptune Console
Sega Neptune Mod
Sega Genesis Mod

How to Build a Sega Neptune

Building a Sega Neptune is no small task, as it requires significant console breakdown and a steady hand. I’ll explain the very basic steps here, but as always, be sure to check my full Sega Neptune mod installation tutorial video on YouTube for detailed instructions. To start, you’ll need to break down the Sega Genesis console to isolate the motherboard. Desoldering the board is a must, and you’ll also have to drill near the Genesis motherboard to remove the cartridge connector, so be as careful as possible. Similarly, you must break down the 32X, and after removing the existing ribbon cables, desolder the two ground wires and one VCC wire, then reconnect them to the other side of the board. After that’s done, you’re free to replace the original ribbon cables with our fancy extended ones.

With that complete, it’s time to prep the Genesis motherboard for the triple bypass installation. Unfortunately, these steps will vary greatly depending on what model Genesis you have, so be sure to consult these triple bypass installation steps from zaxour for your console-specific instructions. From there, it’s all about wire management, which can made much easier with three DIN breakout boards. With that complete, you can now use your rubber standoff spacers to create a gap, as it’s time to connect the 32X board to the Genesis cartridge slot.

If all goes according to plan, it’s time to move on to powering the boards, which can be accomplished by soldering the terminated wire directly to the power connector pins on the Genesis. Moving on, solder your DIN breakout board assembly to their respective spots. With that done, you can now solder the cartridge connector and drop your finished boards into the Neptune shell. After properly attaching the power and reset extenders on the top shell, you’re free to screw everything into place and admire your hard work!

Sega Genesis Mod
Sega Neptune Mod
Image 6 logo

My Thoughts on the Sega Neptune Build

After going through the admittedly tough modification process, I’m absolutely elated by the final product. The attention to detail on the Neptune shell is impeccable, making it a feast for the eyes. In terms of features, this mod delivers exactly what it promises; a powerful Sega Genesis with the ability to play 32X games. There’s no need for a ton of extra bells and whistles, since having a pristine, fully functioning canceled Sega console is more than enough.

Sega Genesis
Sega Neptune

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