Botched Mega Drive / Mega CD Switchless Modchip? - Tech sleuth wanted

Hi everyone. I recently purchased a Mega Drive 1 / Mega CD 2 combo (both EU) with a three-region switchless mod, but it doesn't work exactly as hoped and I'm wondering if someone could help shed some light on the issues I'm experiencing.

First up, the Mega CD side of things works exactly as expected i.e.:
Red: EU PAL BIOS, loads only EU PAL games (Tested with Sol Feace and Road Avenger)
Green: JP NTSC BIOS, loads only JP NTSC games (Tested with Dennin Aleste)
Orange: NA NTSC (...you get the idea)

So far, so good. However, I have a modest collection of Japanese Mega Drive carts, but all the stuff that is region-protected is hitting a brick wall. Mainly:

Bare Knuckle 2: Works only on Red (EU) - in English (as "Streets of Rage 2"). I recieve a region lockout notification on Green (JP) and Orange (NA).
Dynamite Headdy: Bizarrely, works only on Red - in Japanese (i.e. has text before bosses and different level cards) Region lockout on Green and Orange.
Sonic 3: Displays "Developed to work only on NTSC systems" message on Red, Green and Orange.

I got this console combo as an upgrade from a switch-activated Mega Drive 1 (Again, an EU model), so I have some idea of how the software I have should be behaving (i.e. Bare Knuckle 2 in Japanese or English, Sonic 3 working at all). I'm also confident that I've not rounded up a selection of PAL Asian imports or something weird (Japanese manuals, covers, carts).

While I can actually play all of my current collection (thanks to no EU lockout on two games, and the fact that Sonic and Knuckles bypasses the region lock for Sonic 3), there's bound to be games I may get in future that won't have some lucky workaround. Plus, I just want the Mega Drive side of things to work correctly.

Does anyone have any idea what could have happened? Perhaps a soldering error? (there are differences in certain models)? I've not soldered anything in the last 15 years, but I'm happy to open the console up and perhaps have a poke around if someone has any good ideas...

Mega Drive is a PAL-I 1600-05. Mega CD is MK-4102-50

 

I think this has to be a connection error...

50/60 EN/JP
0 0 Not used (would be 50Hz, JP)
0 1 50Hz / En ("Red" - PAL)
1 0 60Hz / Jp ("Green" - JPN)
1 1 60Hz / En ("Orange" - USA)

So the wires aren't transposed - if they were, then PAL mode would function as Japanese. Can you see the video mode changing? I'm wondering if the console is stuck on 50Hz for some reason...

 

I stuck in a PAL cart (Sonic 1) and NTSC-J cart (Puyo Puyo Tsu) to test, and it seems to behave how I would expect:

• Cycling LED through each region with a long press of the reset button gave expected hz (Green and Orange = 60hz, Red = 50hz i.e. slow music).
• A shorter press of the reset button allows me to switch to 50hz/60hz contrary to the regional default. This preference is retained after power on/off but if you cycle the regions, you'll pop back to that default

As an additional check that only just occurred to me, I've decoupled the MD from the Mega CD. All the results tested thus far apply to the console regardless of whether the Mega CD is connected, unfortunately.

Figured it's best to open the MD up and show off what it looks like (aside from noting where the work has been done, I can't really interpret these myself yet).

Wires soldered to expansion slot:


Wires soldered (and tracks cut?) to major chips and what I assume is some kind of region select:


Wires soldered in vicinity of power switches:


Overview of full board (sorry, this one came out blurrier than I was expecting):

 

It all looks plausible to me - those two wires on the expansion slot presumably select the correct boot ROM in the Mega-CD (which appears to be working correctly) - the wires soldered to the area marked "JP1" to "JP4" are the region select for the console. The blue wire soldered to the reset switch is the input that selects the mode and the red green and black wires running towards the front of the console presumably connect to the power LED.

If you have or can borrow a meter, try measuring the voltage on the green wire soldered to the JP1/JP2 positions - this should be high (about 5V) in PAL and US modes and low in Japanse mode - the yellow wire is the 50/60Hz select, and from your description this appears to be operating correctly.

 

Haven't had any luck finding a meter unfortunately (my housemate apparently lost his, and no-one else seems to own one). Is there anything I can do regardless of whether I have visibility on what's going on?

 

Come on people why do these things if there's a modded BIOS which reads all discs you can use...

The very few discs it doesn't work with actually go out of their way to check which BIOS the system is running.

The traces near the wires you placed actually run "hot 12v" from the power plug (used to signal the CD that the MD unit was powered on) and running signal wires near them isn't really safe. They were left unconnected for a very good reason, you see.