PU-23 DFO installation diagram (dual frequency oscillator)

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 PS1 dual frequency oscillators click here, for more information about PS1 mods click here.

PU-23 DFO installation diagram

There is just a single diagram below. It shows the top side of the console board. It doesn't really make much sense to try installing it onto the bottom side of the board because there isn't access to the CLK line.

The small 220 ohm resistor marked in orange needs to be removed. This will uncouple the onboard oscillator from the graphics chip. You will also need to make sure that the DFO board isn't making contact with any of the metal shielding on the console.

Most of the points are pretty straightforward to solder to. The one main exception would be the S0 line. S0 requires soldering to a via hole (or a leg of an IC).

Click on the images to see them in a higher resolution.

PU-23 DFO installation diagram (top)

Installation tips

Here are some tips I have for you when you are installing the DFO onto your PU-23.

  • Cut your wires to be as short and direct as possible.
  • Install onto the top side of the board.
  • You can remove the 220 ohm resistor on the console by heating it up with a soldering iron. Quickly switch between heating up each side until it comes loose.
  • If you have a hot air rework station you can remove the IC204 clock chip and use the onboard 220 ohm resistor. Remove the clock chip, leave the 220 ohm resistor installed, and then connect CLK from the DFO to the crystal side of the 220 ohm resistor.
  • To solder to a via for S0 you'll want to carefully scrape off some of the solder mask from the top of it with a small knife.