MK4 Kick Harness Mod For JPAC & 7 Button Layout

[Nephasth]

I did this mod for fellow member rapomstage3. He recently acquired an MK4 and is currently in the process of converting it (while maintaining the ability to convert back) to house MK4 and MAME (using a JPAC). He was asking how to connect his kick harness to the JPAC without hacking it up. He also made a CP with a seven button layout and wanted to make both middle buttons Block for MK4. I offered to do this mod for him and he shipped me his kick harness.

This mod contains three modifications to the factory harness. Wires needed to be added to the CP end of the kick harness for the 7th buttons, a connector needed to be installed near the PCB end of the harness to change between MK4 and the JPAC, and the new button wires needed to be tied into the Block wires of the JAMMA harness.

I will try to explain everything in as much detail as I can to help out those who have never done anything like this before. First I’ll cover the tools and parts used to make this mod.

These are my wire strippers of choice. They’re able to strip wires from 16-26 AWG. The wires in the factory harness are 24 AWG, and the wires I added to the harness are 18 AWG.


These are the crimpers I use to crimp terminal pins and other style connecting pins onto the ends of wires.


Here are the connector housings, connector pins, and style of quick disconnect I used in this mod. The connectors are Molex Micro-fit connectors and can be bought on various sites (DigiKey and Mouser). The 2 pin connectors are part numbers 0436450200 and 0436400201. The 10 pin connectors are part numbers 0436451000 and 0436401001. The pins for the male connectors are number 0430300001 and the pins for the female connectors are number 0430310001. I don’t have a part number for the quick disconnects, but I purchased them and their insulation sleeves from Bryan at Paradise Arcade Shop (highly recommended vendor).


You can see the size difference between the connector pins and quick disconnects. Different dies for the crimpers are required to crimp each of these properly.


Here are the different dies used in the crimpers. The ones on the table are used for larger crimps (quick disconnects) and the smaller ones (part number HT-236-2C4-DIE) are used for smaller crimps (connector pins).


That covers tools and parts used. Here is rapomstage3’s CP with his seven button layout. Each button is labeled for reference when viewing the pics of the harness.


Now for the mod. First I cut the kick harness near the PCB connector.


Stripped the wire ends for the connector pins.


Crimped the connector pins to the ends of the wires.


And installed the connector pins into the connector housings.






There are a few unused wires in the main body of the harness (from the PCB connector to the CP connector). I decided it would be best to take advantage of these unused wires. However, from the CP connector to the controls, these wires are absent, and I needed to add a couple of wires for the new 7th button (in this case #5 or Extra Block). For the wires I needed to add to the harness, I disassembled this cable. Each wire inside was 18 AWG.


The CP connector is an Insulation-displacement connector, which makes it easy to add and remove wires to the connector without crimping. The wire (unstripped) gets pushed down into the pin and the pin cuts into the wires insulation making contact with the wire. To access the pins the top cover snaps off the connector. NOTE: These pics of the IDC were taken after I installed the Molex Micro-fit connector, but they show the IDC well.




However, the wires I added are too big for the connector, so I had to improvise. I removed the two unused wires I planned on using from the CP connector and added (just like the 10 pin connectors) a 2 pin Molex Micro-fit connector. Used two new wires for the mating connector, these will run up to the Extra Block buttons.


I cut these two new wires to the same approximate length as the other button wires. Slid the insulation sleeves onto the wires and then crimped on the quick disconnects.


Now back to the PCB end of the kick harness. I cut the two wires of the kick harness I used for the Extra Blocks right at the edge of the label (to help hide and secure the unused end of the wires).


Installed another 2 pin connector to these wires. We’ll call this connector the Extra Block connector.


Used new wires for the mating connector. These wires will splice into the block wires of the JAMMA harness. I left these wires plenty long to give rapomstage3 some flexibility on where he splices into his JAMMA harness.


Next I made the JPAC end for the harness. Same process as the first 10 pin male connector, but with new wires.


What wires go to what buttons.


The JPAC end next to the MK4 end for comparison. I left 2 feet of wire off the end of the connector to give rapomstage3 the option of mounting his JPAC pretty much anywhere in the vicinity of the JAMMA edge connector.


HOW THIS HARNESS IS USED:
When playing MK4, the MK4 harness end will be connected to the kick harness and the Extra Block connector will also be connected. To switch to MAME (via the JPAC) disconnect the MK4 harness end (the Extra Block connector can stay connected) and connect the JPAC harness end. The Extra Block connector of the MK4 harness end will not interfere with the buttons while the JPAC harness end is connected and seven individual buttons will be available for each player. Rapomstage3 mentioned the wanted to install a multi JAMMA board in this cabinet sometime in the future. When he does, a new harness end can be made to accommodate the games he installs in the cabinet and will connect to the 10 pin connector. Also, all the buttons on the kick harness share a ground with the buttons on the JAMMA harness.

I posted this in hopes to help out those who struggle with wiring. If anyone has any questions, please ask and I’m sure someone, including myself, will do our best to help out. The connectors I used for this mod aren't required. You can use any connector or means to connect wires you want, but this should show the basic idea of modding a kick harness for these purposes.

[rapomstage3]

Awesome!

[Nephasth]

Pics fixed...