I had a spare Magical Drop so I threw one together:
If you want to say thank you help
@Hammy source a Data East 233 Custom.
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EDIT: I keep getting PMs about this so here is a more noob friendly guide:
This works with any of the "Data East" games on this hardware:
Magical Drop
Magical Drop Plus 1
Chain Reaction
Joe & Mac Returns
Fix Address Map:
Swap the PLD at 5C with the Osman or Cannon Dancer PLD for this location
Fix Security:
re-write the Serial EEPROM at 3H with data from MAME (this controls whether you get Osman or Cannon Dancer, all other data is the same).
It depends on your setup but you will likely have to byte swap this data when writing.
Wire mod to expand GFX2 ROM space:
Cut the traces to Pin 32 on the EPROM sockets at 13A and 14A, wire these together then Wire them to Pin 9 of the 74LS373 at 11A
Run another wire from Pin 8 of the 72LS373 at 11A to Pin 30 of the EPROM at 13A
new GFX2 ROMs can be burned to 27c322s like this:
mcf-04.14h + mcf-03.14d = 14A
mcf-02.14a + mcf-01.13a = 13A
Wire mod to fix Music speed:
Cut the trace going to pin 5 of OKI audio chip at J13 (the one closer to the center of the PCB), this needs to be cut between the pin and the first via. Run a wire from this pin to Pin 5 of the other OKI chip at J14, alternatively you can also run this wire to Pin 9 of the 74LS74 at H10 as this also runs to Pin 5 of the J14 OKI.
Burn the rest of the ROMs as normal:
Program ROM -> 27c4096/27c4002
GFX1 ROM -> 27c160
OKI Music ROM -> 27c160
OKI FX ROM -> 27c020
Technically this guide should also work if you wanted to convert One of the Data East Games to Gonta 2
If you wanted to convert One of the Data East Games to Charlie Ninja you can skip the GFX2 Wire mod step
If you wanted to convert any of the Data East Games to any other Data East game you ignore both the GFX2 Wire mod Step and the Music Wire mod step (but you'll still need to do the 5C PAL and Serial EEPROM)