PU-23 MM3 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 MM3 chips click here, for more information about PS1 modchips click here.

PU-23 MM3 modchip installation diagram

MM3 chip pinout

PU-23 MM3 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.

  • You don’t need to connect pins four and two.
  • 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.

  1. William Quade (me) (I’ve used this diagram many times and haven’t had any problems with it)

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.

Here are some installations I’ve done on some SCPH-9001’s:

This first image shows a cleaner way to install the chip with six wires. I probed the board with a multimeter to find alternate points to solder the wires to that are much closer together. I use the capacitor to the bottom to get the VCC and GND (pins 1 and 8) connected to the chip with really short wires.

PU-23 MM3 install

Below  are a couple of messier 8 wire installs I did using points on the diagram This installation works, but the wires are much longer than they really need to be.

SCPH-9001 install  SCPH-9001 install

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Curt
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Curt

Hi William, I cant thank you enough for all the work you did here on your site, I do appreciate it. I had the choice of modding my original 1001 or a 9001 which I know to be a little tougher so not wanting to touch my baby (the 9001) I went for it on the 9001 and it booted up first time no problems thats to you awesome and straight to the point diagrams. Cheers mate!! Curtz – I think I may have purchased the chip from you as well, any recommendations for a similar chip that will allow… Read more »

John
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John

William,
I recently purchased and installed a chip for my 9001. After installation, when I put in a disk it tries to spin for around two seconds and then stops, remaining on the main menu page. It isn’t the drive motor or laser as I have already tried putting in a different optical lens/laser drive assembly. I was curious if you had any ideas as to what could be the issue.
Thanks

Nathan Face
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Nathan Face

Hi William,
I’m having problems with my instillation. I’ve tried the discs on other systems and they play perfectly and official PS discs play fine after the install. I don’t see anything bridged, Can I send you pics somewhere and maybe you can tell what I have done wrong?

Dave
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Dave

Successfully completed. Hardest part is of course not bridging the pins on the IC. I did bridge the first two pins, and used a piece of solder wick with a chisel tip iron and a bit of fresh solder [on the iron] to pull the bridge from the pins. Be sure to check with a multimeter after removing the bridge to be sure you got it all. IIRC, there was in the megaohms of resistance on those first two pins. Also, use your meter to check the pins on the PIC 12C508 after installation to ensure no pins are shorted.… Read more »

Brett O
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Brett O

I just installed a 12C508A into a model 9001 / PU-23 and I tripple checked my wiring which seems good and followed this “dummy proof” guide. However, when the PlayStation powers on, the cd drive keeps spinning. Disc or no disc it just jeeps spinning… so the question. what Did I do wrong???

Thanks

Luis
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Luis

Just wanted to say thanks I bought youre chip off eBay and installed it using this guide and it worked fine first go and this was my first big solder job. Just had to practice soldering to the small surface mount parts on an old non working psone. Great job with everything keep up the good work

Nick
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Nick

What is the point of connecting pin 2 in the images if you go on to say that you don’t have to connect pin 2?

Pietro
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Thanks for this guide, it works with my scph9002. One question for you: why we don’t need to connect pins four and two? What are they for? I have soldered pin4, but pin2 is very hard…

Jacob
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Jacob

Hi William, I have a model scph-9001 console with a PU-23 motherboard. My original laser assembly was broken and i replaced it with a model scph-5501 laser assembly. Would the MM3 work with this installation diagram? Thank you.

Andrew
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Andrew

Installed yesterday, just needed a reminder on where pins 5-8 on the MM3 PIC were. Thanks.

Doug Plummer
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Doug Plummer

Installed it in my 9001 and it works great. Also the can you explain if pin 2 and 4 hurts to have them hooked up?

Matt
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Matt

Thanks for your efforts mate 🙂 Good resource. I just installed an mm3 in an Australian PAL 9002 unit. It would not work without pin 4 being connected though. Didn’t need pin 2.