I recently picked up some Sega mahjong panels. The standard seems to be a 12 pin and 10 pin AMP/TE connector that doesn't actually plug into anything directly. (I'm sure it probably plugs into a City with a Mahjong harness or something equivalently old.)
Anyway to use a mahjong panel with a Sega JVS I/O there's a few adapter harnesses depending on your cabinet.
With a Naomi/Net City/New Net City you want harness L90-04930A. This connects the mahjong panel to the P1 controls and the 8 pin output connector.
For older Sega cabinets (Astro, Blast, Megalo) with the JAMMA JVS I/O you need two adapter harnesses.
L90-04931A connects the I/O to the cabinet. You also have to change the jumper near the 14 pin connector on the I/O to switch it to enable outputs.
Then L90-04932A connects the mahjong panel to P1 and the extra buttons connector.
Anyway to use a mahjong panel with a Sega JVS I/O there's a few adapter harnesses depending on your cabinet.
With a Naomi/Net City/New Net City you want harness L90-04930A. This connects the mahjong panel to the P1 controls and the 8 pin output connector.
For older Sega cabinets (Astro, Blast, Megalo) with the JAMMA JVS I/O you need two adapter harnesses.
L90-04931A connects the I/O to the cabinet. You also have to change the jumper near the 14 pin connector on the I/O to switch it to enable outputs.
Then L90-04932A connects the mahjong panel to P1 and the extra buttons connector.
