Thanks for the guide and appreciate the details.

Is it possible to just replacement the cartridge holder unless the through hole connections are broken? This adds many wires which could cause problems such as shorting, electrical hazard, etc... Maybe a continuity test between each corresponding through hole connection and point could determine the problematic pins so that only a few wires need soldering and attaching.

Warning 1:

If soldering, ensure each wire has plenty of insulation left so that event with movement of the wire, electrical shorts are not possible.

Warning 2:

Also, ensure the n64 is unplugged and the power supply is fully disconnected from the back of the unit before attempting this for electrical safety and to prevent damage to the unit. Additionally, wait a while to ensure any capacitors are discharged before disassembly as well for the same reasons (not sure how long). The unit unplugged is shown here.

Thanks for writing this guide up. Your many tips are good. The one warning I would give is to not connect two batteries in parallel with significant voltage differences and to safely dispose of batteries connected in this way (careful of overheating, battery expansion/explosion in any case so thanks for the safety glasses tip). Maybe the batteries are not directly connected in parallel unless parity battery means something else in this context depending on the PCB layout. The max voltage difference of batteries would depending on max amperage specs of the battery and resistance and so on.