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To put this project in perspective before we begin, here's a warning: This modification VOIDS the warranty on your console! This project requires familiarity with soldering techniques, handling static-sensitive devices, and a strong heart. Do not attempt this unless you have read this article completely and understand the procedures described in it. You can probably find someone to help you with this who is familiar with these types of projects if don't have this kind of experience. Furthermore, DON'T call Sega of America expecting them to confirm the process or help you out with problems - just like the Secretary, they'll deny all knowledge of your mission should any of your IMF force be caught or killed... Their technicians WILL NOT give any specifics of the system.
On the Genesis I and Mega-Drive (the Japanese version of the Genesis) motherboard there are four jumpers labeled J1 through J4. Two of these are shorted to each other on the bottom of the motherboard. The left one (labeled J2) is closed (shorted to ground) in a Genesis. The right one (labeled jumper J3) has a capacitor across it. (This is exactly opposite in a MD.) To make a Genesis into a MD or visa-versa just swap the state of jumpers J2 and J3, i.e.. short J3 to ground and cut open J3 and place the capacitor across J2 instead of across J3.
Start by removing the six screws on the bottom of the console and separating the two case halves - be careful of the wire connected to the power on L.E.D. on the top half of the case! Remove the shielding from the motherboard and then remove the motherboard. Locate the set of jumpers labeled on the top of the motherboards J1 through J4. J2 and J3 should look similar to the diagram in the following illustration:
To build the switch, get a DPDT toggle switch ON-ON (like a Radio Shack 275-663). The two middle contacts are the poles (commons). Desolder the capacitor's positive (+) side from the motherboard and use a sharp X-acto knife to cut the trace connecting J2 to ground (or J3 to ground on a MD). Make the connections to the switch as shown in fig. 2 (some 4-conductor phone wire is ideal for this).
Be careful of the polarity of the capacitor, it is an electrolytic-type that has a clearly marked polarity: make sure you don't swap them! On the bottom of the motherboard where jumpers J2 and J3 are shorted to each other is the minus-side of the capacitor, so in the drawing above the top side is positive (+) and the bottom is negative (-) for the capacitor.
For those of you not used to working with solid-state devices: NEVER, ever touch a chip unless your are familiar with handling static-sensitive devices! NEVER switch language modes with the console powered-up! And while we're on it: DON'T use the cartridge-swapping tricks where you pull out and insert cartridges while the console is on. This can FRY both the console and the cartridge; moreover, the risks far outweigh the benefits.
Whether or not a game plays in Japanese (or any other language for that matter) is determined by what's burned into the ROM (the cartridge for those who don't speak tech.), so not every cartridge will come up in Japanese. Also, don't expect some radical change in gameplay, new endings, etc. While all of this is possible, it is not very common, and I think you will find it less likely in large (8-Mbit or larger) or newer cartridges, where ROM space is at a premium and extra code is a liability.
Compatibility List
Cartridges that have an alternate language: Forgotten Worlds, Gaiares, Ghostbusters, Ghouls 'N Ghosts, The Revenge of Shinobi, Thunder Force II, Quackshot.
Cartridges that are compatible in Mega-Drive mode but do not have an alternate language: Alisa Dragoon, Altered Beast, Castle of Illusion Starring Mickey Mouse, Columns, Fantasia, Golden Axe, Golden Axe II, Herzog Zwei, Michael Jackson's Moonwalker, Phantasy Star II, Phantasy Star III, Phelios, Shadow Dancer the Secret of Shinobi, Sonic the Hedgehog, Star Control, Stormlord, Strider, Sword of Vermillion, Target Earth, Taz-Mania, Thunder Force III.
Cartridges that are not compatible in Mega-Drive mode: Populous.
The author is not responsible for damages resulting from the use (or misuse) of information contained in this document.
SEGA GENESIS and MEGA-DRIVE are registered trademarks of Sega of America, Inc. and Sega of Japan, Inc., respectively. All games are registered trademarks of their respective companies.
A special thanks to Frank Overman (etmfrov@sunbeamfs.ericsson.se) for the timely information. (The Quest is over!)
May the forces of evil become confused on the way to your house.
Dark Grue <darkgrue@iname.com>
Copyright © 1992 by David G. Hesprich (Dark Grue). All rights reserved.