The Wondermega is one of the nicest ways to run Mega-CD games: Sega and JVC's 1991 Japan-only deck that combines a Mega Drive and a Mega-CD in one unit, with a motorised CD lid instead of the usual flip-top or sliding tray. This is my second HWM-5010.
It reached the bench with leaking capacitors and a CD tray that would only open aided by hand. The fix was a full recap of all five internal boards, a clean and lube of the laser assembly, and a new CD drive belt. The CD side got particular attention: the laser pickup PCB, which carries the JVC Optima-5 pickup, was recapped, the CD-ROM/servo board too, and the traverse gears were greased with Molykote DX paste.
The result is that both sides work and, with the new belt, the motorised tray opens and closes on its own again. I ran Silpheed off a real Mega-CD disc to prove the CD side, and Contra Hard Corps on the cart side.
If you have serviced a Wondermega or a Mega-CD drive, did a new belt sort your tray problems on its own, or did it take more than that?
I want to start getting into sega cd imports. What’s the easiest way to get started. Is there anyway to play them on a US system that isn’t a huge pain in the ass. Or is getting a Japanese sega cd the easiest option? With that would I need a mega drive then if I use a Japanese sega cd?
Side note, wow Ecco really benefits from that improved soundtrack. Love the weird eerie feeling of this game so much :)
Next step now is to leave it on for a while to see if it successfully charges up the battery inside. I’ll check later and see if it holds a charge. Then time to start rippin’ 😁🤙
Like with my recent post about Popful Mail I have also made a version 2 of my Vay PAL conversion. The original while techincally working had lots of audio issues. These are now 99.9% sorted with only the odd split second of a line trying to repeat once or twice.
Additionally for both PAL and NTSC I have increased the XP and Gold gain by x 4 to match the 1 - 4 encounter rate hack. So if you use either the PAL or NTSC versions it has the UnWorked mod and the 1 - 4 encounter rate but boosted by x 4 XP and Gold so you don't need to grind to keep up.
The PAL version has been fully tested on original hardware using a CD and had tests with an Everdrive Pro as well.
I'd like to share a project I've been working on for quite some time. It will be released as open source on GitHub under Electroanalog VICE, but I wanted to give the Sega CD community a first look.
Neptune BSS TX/RX consists of two independent components.
The TX board is installed in the Genesis and provides Region Mod functionality while transmitting the selected Genesis region during startup.
The RX board is installed inside the Sega CD, where it receives the startup command and automatically selects the corresponding BIOS bank.
The goal behind Neptune BSS TX/RX was to solve one of the biggest drawbacks of existing Sega CD Multi-BIOS mods, the need to cut and reroute expansion bus traces between the Genesis and the Sega CD.
Neptune BSS TX/RX takes a completely different approach.
Instead of routing address lines between both systems, it communicates the selected Genesis region during startup over a single native connection already present between the Genesis and the Sega CD. The RX board then selects the corresponding BIOS bank. Once the BIOS bank has been selected, no further communication is required.
The system supports four BIOS banks:
🇺🇸 North America
🇯🇵 Japan
🇪🇺 Europe
Fallback (default compatibility BIOS)
The Fallback BIOS bank ensures full compatibility with an unmodified Genesis. If the RX board does not receive a valid startup command, it automatically selects the Fallback BIOS bank, allowing the Sega CD to boot normally.
TX (Genesis)
The TX firmware runs on a PIC16F630, the same microcontroller widely used in classic Genesis Region Mods.
Besides providing the traditional Region Mod functionality, it automatically transmits the selected Genesis region to the Sega CD over a single native connection during startup, allowing the RX board to select the corresponding BIOS bank.
The last selected region is stored in the PIC's internal EEPROM, so it is automatically restored every time the console is powered on.
Features include:
Reset button controlled Region Mod.
Automatic restoration of the last selected region after power cycling.
Automatically transmits the selected Genesis region to the Sega CD.
In-Game Reset (IGR), including support while running in Master System mode.
Uses only one existing native connection to the Sega CD expansion interface.
RX (Sega CD)
The RX side consists of a compact decoder board that intercepts EPROM address lines A16 and A17 while tapping a small number of existing motherboard signals.
It works together with a 27C4096 EPROM, automatically selecting the appropriate BIOS bank according to the region received from the Genesis.
During startup, the RX board listens for the command transmitted by the TX firmware. If a valid command is received, it selects the corresponding BIOS bank. Otherwise, it automatically selects the Fallback BIOS bank.
This means a Sega CD equipped with the RX board remains fully compatible with both modified and completely stock Genesis consoles.
Installation only requires:
Replacing the original BIOS with a 27C4096 EPROM.
Lifting and rerouting EPROM address pins A16 and A17 through the RX board.
Tapping the required signals on the Sega CD motherboard.
Communication over the Native Audio Connection
On Sega CD Model 2, Neptune BSS TX/RX uses the existing B27 connection, which normally carries the Genesis audio signal.
Communication takes place only once during approximately the first second after power-on. After the BIOS bank has been selected, the line immediately returns to its normal audio function and no additional data is transmitted for the remainder of operation.
The transmitted signal is extremely brief and, in most cases, completely inaudible. Even on systems where it can be noticed, it is limited to a very short moment during startup before normal operation begins.
On Sega CD Model 1, the same connection is unused, making the implementation even simpler.
Why this approach is different
Uses only a single native connection between the Genesis and Sega CD.
No expansion bus traces need to be cut or rerouted.
Works with both Sega CD Model 1 and Model 2.
Automatically synchronizes the selected Genesis region with the appropriate Sega CD BIOS bank.
Stores the last selected region in non-volatile memory.
Fully compatible with unmodified Genesis consoles through the Fallback Sega CD BIOS bank.
Cleaner installation than traditional Multi-BIOS implementations.
The attached photos show:
RX decoder PCB (front).
RX decoder PCB (back).
RX decoder installed inside a Sega CD.
EPROM with address pins A16 and A17 rerouted through the RX board.
I'm currently finishing the documentation and preparing the GitHub release.
I'd really appreciate any feedback from the Sega CD community.
Would this be something you'd install in your console?
A couple of years ago I shared my PAL conversion of PAL so it would work on real hardware without any mods or flashcarts needed to change the BIOS. That original conversion had some graphical issues in cutscenes but they have now been fixed for the V2 release!
This has been tested with a CD and also with an Everdrive Pro thanks to a friend of mine.
Just got my new Sega CD and while I'm waiting on the power supply (BTW gametrog item shipped!) I figured I'd clean it up. Honestly though it barely needed it. Whoever owned this before kept it in great condition. But I did the full disassembly, soap and water bath I always do and dusted and cleaned up the board with isopropyl as well.
While I was in there also cleaned up and re-lubed the cd drive assembly and laser and checked the fuse and battery. Fuse was good but the battery will definitely need replacing so that'll be my next project.
Got two games with it so can't wait to test this puppy out!
P.S. Anyone know specifically what that daughter board is for from Sega? I did a little googling but couldn't come up with a concrete answer of what it fixed.
(I'm not sure if r/SonicTheHedgehog would allow this thing being posted, so I posted here)
This is an mockup box art of a game called Amy Rose for the Sega CD
If you guys don't know about how would this game look like, I could tell you guys that this game includes elements of Chinese mythology and traditional Chinese festivals or other cultural elements, and it was also inspired by Journey to the West.
The way the FMV of the stages is done looks so perfect and matches the foreground graphics so convincingly, that if you were ignorant to how the SEGA-CD works, you'd swear it's all real-time 3D. The fakery on display is just THAT damned good.
Does anyone know what the capacitance is for C22 and C23 on the sub board? On the Mega CD manual it shows both as 0.1 uf on the list of parts, but on the schematic itself it says 0.022 uf? Just want to be sure before replacing them since the previous owner likely used the wrong power supply on it and blew the fuse as well as these capacitors. Thanks!
I accidentally discovered something interesting while playing Sonic CD on Kega Fusion using a real CD drive.
I first booted the game with my burned Sonic CD, started a level, then ejected the game disc and inserted a CD containing my own music playlist. As long as the music CD stayed in the drive, the game's soundtrack was replaced with the corresponding audio tracks from my playlist.
To keep playing, I had to swap back to the Sonic CD whenever the game needed to read data, then switch again to the music CD whenever I wanted my custom soundtrack to continue.
I didn't expect Kega Fusion to handle disc swapping like this. Has anyone else tried this before?
