Open source Sega Mega-Tech reproduction game carts

mourix

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246CR
During my restoration I found game prices for this machine had skyrocketed and ended up reverse engineering original carts to make my own cheaper copies.
Because sharing is caring: I've open sourced the designs for everyone here!

There are two most common carts for the Mega-Tech:
  1. 171-5782 - 4 Megabit Mega Drive based games
  2. 171-5783 - 1 or 2 megabit Master System based games
1711310264552.png

For both designs I have made two versions:
  1. A 1:1 carbon copy "repro" version, which is the result of my reverse engineering.
  2. An optimized "redux" version, which removes unused parts and adds features to make homebrew carts easier.
I invite everyone to make their own :)
 
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mourix

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246CR
How to assemble the Redux PCBs :)

2024-04-02 19.09.25.jpg

To assemble a single cart you need:
  • 1pc Japanese Mega Drive shell.
  • 1pc Redux PCB:
    • 171-5782 for Mega Drive based games.
    • 171-5783 for Master System based games.
  • 1pc 47uF 16V electrolytic capacitor.
  • 2pcs 22nF ceramic/MLCC capacitors.
  • 1pc Menu EPROM - 27C256.
  • 1pc Game EPROM:
    • For Mega Drive:
      • 27C400 - 512KBs (4Mbits)
      • 27C800 - 1MBs (8Mbits)
      • 27C160 - 2MBs (16Mbits)
      • 27C322 - 4MBs (32Mbits)
    • For Master System:
      • Remove the ROM from an original Master System cart as they contain logic.

Let's make a Spider-Man vs. The Kingpin cart (4Mbit Mega-Drive based)

First, order the PCBs on JLCPCB. You upload the 171-5782_Redux_Gerber.zip file and put in the following settings:

Screenshot 2024-04-03 121518.png

Next up is programming the EPROMs.
I used a Xgecu T48 Programmer. It can program 27C256 directly but needs a 16-bit adapter for the game ROMs. A label printer is handy too.

2024-03-28 16.27.23.jpg

Unzip your *legally* dumped ROMs, with the 32kb ROM always being the menu one:

Screenshot 2024-03-28 161957.png

Now, burn both of them.
The 27C256 is mandatory for the menu ROM, but you can use a larger EPROMS for the game ROM. I used a 16Mbit 27c160 for this 4Mbit game.

Screenshot 2024-03-28 162508.pngScreenshot 2024-03-28 163152.png

Note: the quality of EPROMs I got off Aliexpress has been really hit and miss. You can ignore a check ID error, but be sure the flash finishes like this:

screenshot-2024-03-28-163213-png.18384
 

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mourix

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246CR
Finally, soldering time (don't forget the solder jumper!):

2024-04-02 19.16.54.jpg

And enjoy your game:

2024-04-02 19.22.39.jpg

To finish things off, put it in a shell:

2024-04-02 19.19.41.jpg

And maybe use that label printer to mark the shell:

2024-04-02 19.20.51.jpg
 

mourix

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Credits
246CR
What about the Master System based carts?
  • Same JLCPCB settings as before, but order the 171-5783_Redux_Gerber.zip this time.
  • Burn the 27C256 menu EPROM.
  • Desolder the game Sega ROM from a real Sega Master System cart.
  • Solder everything to the new PCB, noting the solder jumper for 1M ROMs.
2024-03-23 23.15.06.png
 
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Adamski

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Where do I get parts?
Good job,jolly good effort you put into this.Out of curiosity too,how easy is it to repurpose a megatech cart (ice hockey or basketball) to a more exciting title?
 

mourix

User
Credits
246CR
Where do I get parts?
Good job,jolly good effort you put into this.Out of curiosity too,how easy is it to repurpose a megatech cart (ice hockey or basketball) to a more exciting title?
There is an old tutorial here, but even the value of Basketball/Hockey is much higher than the the cost of one repro above, not even counting the desoldering efforts.
 

mourix

User
Credits
246CR
2024-04-23 00.11.17.jpg

For the Mega-Tech Mega Drive Converter you need:
  • 1pc Mega Drive Converter PCB.
  • 1pc 47uF 16V electrolytic capacitor.
  • 1pc 22nF ceramic/MLCC capacitor.
  • 1pc Menu EPROM - 27C256.
  • 1pc "2x32P 2.54mm pitch edge connector" or "Mega Drive cartridge connector".
Besides of the PCB, all of these parts are available from Aliexpress.
 
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