PU-23 Mayumi v4 modchip installation diagram

The last version of the original PlayStation 1 design was the SCPH-900x. Most of these consoles have PU-23 boards inside. The most notable difference between the 9000 series and earlier consoles is that Sony removed the parallel IO port on the back. They also shrunk down the size of the board significantly.

For more information about Mayumi v4 chips click here, for more information about PS1 modchips click here.

PU-23 Mayumi v4 modchip installation diagram

MM3 chip pinout

PU-23 Mayumi v4 modchip installation diagram

Above is the diagram for the PU-23. Pin four is located towards the top left side of the board.

Since the diagram isn’t the clearest I’d like to mention that the second pin connects to the top most pin on the left row of pins on the chip. Pin three connects to the left contact on the middle resistor, and pin six connects to the top contact on the left capacitor.

Installation tips

Here are some tips I have for you when you are soldering your chip into the PU-23.

  • Pin 3, and 6 can be tricky. Don’t push on the components with your soldering iron or they might get knocked off the board. You can use tweezers to carefully solder them back on one side at a time, the orientation doesn’t matter.
  • Make sure the wire on pin 3 and 6 don’t come into contact with both sides of the component (this is especially common if you run the wire directly on top of the component).
  • Don’t apply too much solder to pin 2 or you’ll bridge the pins on the chip.
  • Placing the chip where the pin two circle is, or below it, seems to be the ideal location for placing the chip.

Diagram success rate

Here’s a list of people who have successfully modded their console with this diagram. Leave a comment and I’ll add you to the list.

Example installations

This section has photos of some successful installations which you can use to get a better understanding of how everything is wired and positioned.


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