USB-NES Power System Upgrade

USB-NES units sold before May 1st 2022 have a hardware bug that prevents the unit from functioning properly when trying to play newer games like Kira Kira Star Night DX and all the Retro-Bit mapper 268 releases like Metal Storm and the Data East All-Star Collection.

This section documents the steps to fix the problem with USB-NES and provides a link to purchase the upgrade part through Digikey.

What you will need

  • Capacitor upgrade (or else a cap in the range of 470 – 1000 uF)
  • #1 Phillips Screwdriver
  • Soldering Iron
  • Solder
  • Experienced rework time estimate: 20 min.
All the essential tools you need to do the upgrade.


  1. Remove the 6 star head screws on the bottom of the unit with a #1 Phillips screwdriver.
6 screws to unfasten.
Screws removed.
  1. Open the cartridge dust cover door completely and carefully take the unit apart, being mindful to not stress the thin plastic blocker below the micro-USB port or it may break off the bottom assembly.
The plastic piece here is fragile.
  1. Pop the USB-NES board out of the middle assembly.
Pop the circuit board out by pulling the plastic frame towards you while pressing your thumb down in the hole where the red highlighted text in the picture is.
  1. Cut the positive lead (opposite the minus side) on the capacitor to 1/2″ (13 cm). Leave the negative lead the full length, and bend the leads apart as per the pic.
Cut the positive lead at one-half inch.
  1. Tin the ends of the capacitor leads with solder.
Tinning the ends of the capacitor will make it easy to solder it to USB-NES.
  1. Add an excess amount of solder to the GND pin on the blue pill indicated by the right arrow.
  2. Add an excess amount of solder to the 5V rail connected to the power MOSFET indicated by the down arrow.
The goal here is to leave enough solder on the joints so that when connecting the capacitor leads to them it is not necessary to add any extra solder while doing the work.
  1. Solder the negative lead of the capacitor to the GND pin on the blue pill as indicated by the left arrow. Leave 1 mm spacing between the negative lead and the blue pill PCB.
Solder the negative cap lead onto the GND post from the side closest to the C13 & C14 pins for the most accessibility.
  1. Solder the positive lead of the capacitor to the lead on the power MOSFET as indicated by the down arrow.
Solder the cap positive lead to the 5V power rail entering the MOSFET. Nice shiny joints with generous amounts of solder are the goals here.
  1. The capacitor should clear the space inside the middle bracket when reassembling the unit; press the cap down against the USB-NES PCB if necessary.
The capacitor has to clear the height of the plastic bracket here.
  1. Re-assemble the unit by working backwards from step 3 and doing the reverse processes.
  2. That’s it! Now your USB-NES will have enhanced compatibility with new NES/Famicom boardset technology and games.
New NES games like Kira Kira Star can properly work with USB-NES after the upgrade.