PU-20 MM3 modchip installation diagram

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

For more information about MM3 chips click here, for more information about PS1 modchips click here.

PU-20 MM3 modchip installation diagram

MM3 chip pinout

PU-20 MM3 modchip installation 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.

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.
  • Don’t connect pin two of the chip to anything.
  • Pin 4 can either be connected to the pin 4 location in the diagram, or pulled high by connecting it to pin 1 on the chip.
  • 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.

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.

  1. William Quade (me)

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.

This is an installation I did on an SCPH-7001:

SCPH-7001 MM3 installation

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Johnny smythe
Johnny smythe
December 14, 2018 2:49 PM

Hey I picked up the mm3 chip from you off eBay a couple weeks ago (hotdogs_stuff). I have a scph-7001 with the pu-20 board. I installed the chip securely with all the wires measuring less than 3 inches. I did use pin 4 – because you had it connected in the diagram (but I did not use pin 2) I made sure nothing was bridged (I have some experience building boards), unfortunately after the mod my ps1 no longer read discs it just goes to the cd screen. I removed the chip completely and it works normally again. Do you… Read more »

March 28, 2019 9:47 PM

Hello, when connecting pin 6 I accidentally ripped up that trace from the pcb. can I fix this or are then any alternative pins? or is it dead.
it still boots but doesn’t read any disc. I didn’t continue install the mm3.

September 3, 2020 7:49 AM


I have same issue exactly as Johnny smythe, 7001 board and tried 2 chips (MM3), fitted, nothing works (originals or backups) removed originals boot perfectly

Is there a solution for this? do i need to sheild the chip? I have resoldered the first board 4 times using dupont wires, second time i use Kynar, on the replacement chip i use kynar. I know my soldering is perfect!

November 20, 2020 10:59 AM

Hi William,
i bought a scph-7002 (PAL) replacement motherboard.
has the modchip already installed (photo) with 5 wires instead of 7.
I noticed that the diagram is different from yours, in particular I notice that the wire of pin 8 is soldered differently from your diagram and there is a wire for pin 2. in your opinion the chip is not a multimode?

November 20, 2020 11:05 AM
Reply to  William Quade

ok, thanks, i think i will replace it with yours, without unsoldering the points connected correctly with your scheme.
since the wire of pin 4 is soldered to a resistor, I read on your comment that it is possible to make a bridge and solder the wire to pin 1.
If I do so then is that correct? will i always have stealth as a result?

November 20, 2020 11:20 AM
Reply to  William Quade

I beg your pardon but I don’t think I understand, I believe that with an example image you would help me.
Thanks for your help.

November 20, 2020 11:25 AM
Reply to  William Quade

ok, i try to follow the diagram.
Thank you so much.

November 28, 2020 5:18 PM

hi william, i have successfully installed the chip on the board of my psx pu-20 scph-7002. i placed the chip on the board without electrical tape. in a comment you wrote that the card is electronically noisy and can annoy the chip, in fact I have problems with cd backups, while the originals (both pal and ntsc) work fine.
do you think wrapping the chip with electrical tape solves the problem?
thanks. juri.