Welcome, Guest!

Here are some links you may find helpful

NES Need help with full FourScore mod use on Japanese Famicom.


Original poster
Jun 3, 2019
AG Join Date
Hey I recently modded my famicom to accept the fourscore, as far as I can tell I'm the first person to at least record themselves somewhere how to do it. At any rate I have 1, possibly 2 issues with how I've done the mod.

How the mod is done:
-Cut the audio line trace on the famicom expansion port near the pin. (The audio out line was chosen because it's rarely used for anything)
-Bridge the D0 line of the first internal controller to audio out pin on the expansion port.
-Wire up a neo-geo extension cord to the FourScore, as all controller pins are now present on the Extension port this shouldn't be hard. Ground to Ground, VCC to VCC, Latch to Latch, D0(1) To D0(1), etc. (please note, some pinouts online for the NES controller refer to D0 as D1. NES controller pinout doesn't have D1)

-Now you have a perfectly working FourScore on your Famicom

This all works fine unless you have the D0(2) line from the internal controller for player 2 hooked up. If that's the case for some reason Player 2 on both the fourscore and internal one can't be used except for the mic. (Player 1,3 and 4 still work on the fourscore just fine) This could obviously be resolved with a simple switch on the console or in the internal controller but I'd rather use something more automatic. How can I do this?

Second issue might be due to only having PAL hardware for the NES as I've read PAL NES controllers pull high instead of low. Normally both Data lines are around ~0.5V on the famicom which with the four score attached D0(2)becomes ~2.5V while D0(1) becomes ~4.5V. When nothing is connected at all it reads a nice and steady 5V. So I imagine there is a conflict. This issue might be the reason why I have the first issue, and using a NTSC FourScore might resolve both issues, but seeing as I don't have a NTSC FourScore I can't test that at this time.

So does anyone have an idea how I could resolve these 2 issues to get the FourScore perfectly working without a switch on the famicom?

If there is intrest I'm willing to make a graphic to show how the mod is done in it's completion so others can follow it.
Last edited:

Make a donation