The second hardware revision of the Sega Genesis (or Mega Drive if you're outside the US) is by far one of the easiest consoles to take apart, it's essentially four layers of plastic and stamped metal with a static mainboard sandwiched in-between. The Genesis used in this guide had already been taken apart 5+ times for various cleaning and repairs and still works like new.
Nevertheless, this guide will walk you step-by-step through a complete teardown of the Sega Genesis/Mega Drive II
PreparationEditBegin by preparing a flat, clean surface to work on, and disconnect any controllers, games, cables and add-ons that are connected to your console. The only supplies you will need besides the console itself are a standard Phillips-head screwdriver and (optionally) something to contain your screws. If your Genesis was recently plugged in to power, it's a good Idea to turn the power on wile the system is unplugged, and let it sit for a few minutes to drain the capacitors before starting. This will greatly reduce the risk of an electrical discharge that could lead to shock or damage to the console.
Getting InsideEditTurn the console over to expose the underside. Remove the plastic cover concealing the expansion slot as shown on the left, and set it aside. You can also remove the red "DO NOT REMOVE" sleeve on the connector itself if you like, although doing so will leave the connector pins more susceptible to damage during the remainder of the disassembly.
Next you will need to remove the four highlighted screws on each corner of the console base. They are a bit tight at first, but should come loose with minimal effort. It may be necessary to turn the console back over and gently tap the it to get the screws to come all the way out of their holes. Once the screws are out, the top cover should lift straight up from the base.
The Cartridge Bay DoorEditSet the base of the console aside and turn over the top plastic cover. Undo the three bronze-colored screws highlighted in the picture below, and lift off the spring-loaded door assembly that protects the cartridge slot.
Set both pieces aside and continue to the next step.
The Upper Heat ShieldEditReturning to the base of the console, you will now need toremove the upper heat shield to gain full access to the system mainboard. Remove all nine screws highlighted in the images on the left, and lift the heat shield straight up from the base. Be sure that ALL the screws are removed before attempting to lift off the heat shield as it's made of cheap stamped sheet metal that has a tendency to bend.
The MainboardEditOnce the upper heat shield has been removed the top of the system mainboard will be exposed, this is where all the consoles working components are. The vast majority of Genesis II repairs and mods will involve soldering something to the mainboard. To remove the mainboard form the console base undo the two large screws on either side of the cartridge connector, and carefully lift it straight off. If you left the "DO NOT REMOVE" sleeve on form earlier you can use it as a grip to hold the board easier without risking damage.
The Console BaseEdit
As one final step, you can remove the plastic cartridge support and lower heat shiled form the base of the console,as all the screws holding them in place have been removed.
To reassemble the system, just follow these same steps in reverse order, here are some things to remember:
- Do NOT let any screws get between the lower heat shield and the mainboard
- Make sure to put the cartridge support back in place before screwing the mainboard to the base
- Check that the heat shields are oriented correctly before trying to tighten them down
- The screws used for the upper heat shield and the cartridge door are identical, it doesn't matter if you get them mixed up
- Be careful not to put screws in too tightly or you can damage the plastic threading