Arcade Collecting > Restorations & repair

Sega Mega-Tech Restoration

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mourix:
Front kickplate cleaned up well after some magic eraser and black permanent marker action. Also added new locks, screws and obligatory Sonic keychain.



The Dutch regulatory sticker plexiglass was cracked up pretty bad. To keep it stock, I just 3D printed some washers to hide most of the damage.

mourix:
Currently I have reverse engineered both the Megadrive and Master System based carts. These are on the way from China as we speak:



I'll do a full write up once I got them in and tested. The plan is a Github for everyone to make their own.

mourix:
In today's update: a warning for people wanting to recap the Mega-Tech PCB.

I wanted to try a recap because my cab sounded like a smartphone. So I made the cap list here and got to work.

I own a decent soldering/desoldering station so usually it's a breeze, but not this time. This board got all the difficulties.. Multilayer ground planes, small through holes, bent leads and thin traces right next to cap pads.

After hours of soldering it does look nice though:



However this is what I was greeted with when I plugged it in. Crapp.. Back to debugging I guess.



NES4Life has a nice write up on this so I knew which area to look at. Finally found the issue:



I added one blue botch wire to the green factory botch wire seas:



But hey, we are back!



But... now the left speaker was dead. After a bunch of digging that was a 3mm track without a connection so a solder blob got it back.

And now I own a nicely recapped Mega-Tech that almost killed it...and still sounds like a smartphone. I guess it was 80's speaker quality all along :dunno

mourix:
Progress update on the homebrew. I want more games in my collection, but even sports ones are getting expensive now. There are some guys selling repro gamecart PCBs, but I want open source everything ;)

For the whole library, we need both a Mega Drive and Master System based cart. The 171-5782 is the common 4M Mega Drive cart, and the 171-5783 is the common 1M/2M Master System cart. 

To get both, these were the sport game victims of the day:



After taking them apart and removing every component, I made scans of both sides of both boards and lined them up in Photoshop.



Based on those master Photoshop files, I traced every track in Altium Designer software until I had an almost 1:1 reproduction of the layout and schematics to accompany.



After lots of tidying up I ordered 10 pieces each from JLCPB. This showed up yesterday:


mourix:
The Sega Mega-Tech is pretty much a Mega Drive glued to an additional Master System that runs the menu screen. To make this duo work, the (same as home version) game rom is placed on a circuit board with an additional custom menu rom that contains the text to fill the menu pages.

The menu rom is a 27C256 that can be had from Aliexpress for cheap. So cheap even that my newly acquired T48 programmer freaked out because the Chip ID on them did not match the painted on manufacturer name.. But I got 3 out of 4 programmed in the end.



For the 4M Mega Drive games, a 27C400 EPROM fits in without modifications. But with me owning like 5 copies of Sonic 1, I just desoldered an original game cart chip.



I put it in the cab and was greeted with the following. YESSSSSSSS!!!!

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