PU-20 Mayumi v4 modchip installation diagram

This board was used exclusively with the SCPH-7000 series of consoles.

I sell Mayumi v4 modchips in my store.

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

PU-20 Mayumi v4 modchip installation diagram

MM3 chip pinout

PU-20 Mayumi v4 diagram

Above is the diagram for the PU-20.

The diagram isn't the cleanest so I'd like to clarify a few points that are unclear. Pin six connects to the bottom left most leg of that chip, and pin five connects to the pad to the left of the white line on the board. Pin four connects to the right side of the capacitor, which is the topmost component in that spot.

The second pin connects to the bottom leg of the right side of that chip. Be careful not to use too much solder, or you might connect two legs of the chip together.

Installation tips

Here are some tips I have for you when you are soldering your chip into the PU-20.

  • Cut your wires to be as short and direct as possible.
  • The high speed clock line (pin 2) needs to be especially short and carefully routed.
  • Placing the chip where the pin eight circle is seems to be the ideal location.
  • Be careful when soldering to pin four, if you apply too much solder, or press too hard, you may knock a component off of the board, or bridge the connection with nearby points.
  • When soldering to pin six be careful, you don't want to apply too much solder and bridge nearby pins on the chip.

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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July 28, 2019 9:15 PM

Good this diagram is work

December 6, 2019 7:32 AM

Hi. It's me. I managed to successfully install the modchip I mentioned that i found on my old dead psone Ntsc-j. I just used the method above. The mm3 version does not connect the pin 2. So now i soldered pin 2 and it worked. Im just curious as to why the wire should be short? Mine was a cm long. Is that enough. I tried my old psx backups ntsc u and they all went straight to the cd player. As you mentioned before this backups wont work because of the additional security on all Japan ps1 after model… Read more »

August 9, 2020 10:50 PM

I tried to install in my ps1 jp, and now the ps1 spins the cd soooooooooooooooooooo fast and it doesnt read. I didnt find any situation on internet. I removed the modchip, and it still continues. Do you what it should be?