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 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.

  • 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.
  • 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).
  • 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 is an installation I have done on a PU-23 board. I used some alternative points for the power and ground connections (pins 1 and 8) for a cleaner installation. Pin 6 is also different but is connected to the same place.

PU-23 MM3 example installation

 

 

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Dave
Dave
April 7, 2018 12:09 AM

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 »

Curt
Curt
March 16, 2018 9:28 PM

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
John
March 26, 2018 12:08 PM

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

John
John
March 27, 2018 12:14 AM
Reply to  William Quade

Thanks for the prompt reply! So I took out the modchip and it still won’t read audio CD-Rs. I just put a new laser and drive motor assembly because I also thought that could be the problem. The drive spins the disk twice like it is attempting to read it but then gives up. If you have any insight on why the unit won’t read audio CDs even without the chip installed let me know!

Nathan Face
Nathan Face
March 26, 2018 8:40 PM

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?

Brett O
Brett O
May 1, 2018 12:25 AM

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
Luis
May 25, 2018 4:20 PM

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
Nick
June 19, 2018 5:00 PM

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
August 12, 2018 12:57 AM

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
Jacob
August 28, 2018 11:46 PM

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.

Jacob
Jacob
August 29, 2018 4:20 PM
Reply to  William Quade

Thank you very much.

Andrew
Andrew
September 21, 2018 10:26 AM

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

Doug Plummer
Doug Plummer
November 2, 2018 6:01 PM

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?

Elder Bog
Elder Bog
December 22, 2018 9:52 AM
Reply to  William Quade

Hi william, i’ve just install the mm3 modchip now, i’ve much experience in soldering, i Made a good clean job. But there si 2 strange things that i’ve ti notice, i hope you can help me: 1) i burn Moto Racer 2 EUR with cue file, the playstation read the disc like a music disc, start the media player software and not the game, i used imgBURN at 10x becouse the disc minimum speed is 10x… 2) i tre ti play ah original disc, it load, but sems that the down button is ever pressed and i can’t do nothing… Read more »

Ryuzaki
Ryuzaki
March 5, 2019 3:19 AM
Reply to  Elder Bog

Elder Bog,
Not to jump in place of William. Try cutting your wires shorter.

Matt
Matt
December 11, 2018 9:24 PM

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.

brian weaver
brian weaver
March 12, 2019 12:23 AM

man i love you easy install with your picture much appreciated works flawlessly

Holger
Holger
July 19, 2019 4:26 PM

Successfully assembled! The schedule works fine but i would appreciate a better image quality. There should also be a ~100 nF capacitor between the power pins on the PIC.

Jvc
Jvc
December 26, 2019 3:07 PM

Hello, long time ago i had a PS1 with PU-18 and 12C508A modchip, but it stopped working at one point through the years. I had bought me a year ago another ps1 with pu-23 but it did not had a modchip. I have tried now to transfer the modship in the new ps1 with pu-23 with the help of the diagrams on the webpage here, unfortunately now it does’nt play anything at all anymore? it always transfers directly to the main menu. i’ve checked the wiring couple of times but can not find any fault in it. Checked with a… Read more »

Jvc
Jvc
December 26, 2019 4:51 PM
Reply to  William Quade

I don’t know much about it i’m afraid, this picture shows the chip as it was installed in the first PS1 (and always worked very well till the laser was worn out)

https://ibb.co/qN3ccFY

Jvc
Jvc
December 28, 2019 12:11 PM
Reply to  William Quade

Thanks for the information. i have tried it with the new wire diagram, but no luck, same result.
Also removed the chip completely again, and also same result, doesn’t play any disc anymore now, so i messed it up probably.
But thanks again for the information and your help.

Jakub
Jakub
June 26, 2020 3:08 AM
Reply to  William Quade

Hello William, right now I’m looking for a modchipped Playstation 1. I’m a newbie in modchips but I found one for a good price, which I think is modchipped just like the diagram you posted above. Is it diagram for the old chip you were talking about or 4 wire diagram for MM3? If it’s the old one, are games like Crash Bandicoot, Spyro and Tony Hawk Pro Skater anti-modchip games? Thank you very much!

Tomas Zartman
Tomas Zartman
February 18, 2020 7:19 PM

I have installed the MM3 mod onto my PU-23 SCPH-9001. After installation, the PS1 no longer spins discs or outputs video. Could I email you a picture of my install to get your input on what I may have done incorrectly? The device does still power on, and worked fully before I attempted to install.

Tomas Zartman
Tomas Zartman
February 18, 2020 7:28 PM
Reply to  William Quade

Thank you. That is the kind of thing I assumed, and this is the first time I have soldered anything before.
https://imgur.com/a/9Jj13pH

Tomas Zartman
Tomas Zartman
February 18, 2020 7:35 PM
Reply to  William Quade

Thank you, I will do so and report back once done! I appreciate your quick reply and help.

James Boggs
James Boggs
May 1, 2020 3:19 PM

Bought one of these from you, and got it installed, and when I kicked my psx on, the disc dive spun up to max speed and stayed there, while the unit didn’t seem to register there was even a disc inside.

I did some tests and eventually removed the chip, and even with the chip out its behaving the same. It doesn’t look like I bridged any, I cleaned up everywhere that wasn’t an open pad.

Any idea where on the standard installation I might have created a problem like that?

Thanks!

Morgan
Morgan
May 13, 2020 2:27 PM

Just used this diagram and it works like a charm! First time soldering something like this too. Thanks for the help!

Johnathon
Johnathon
May 17, 2020 5:40 PM

I Soldered (MM3) to PU-23 to all points, it will boot the back up’s, but have to reset a few times?
Some burns won’t load, just black screen after The intro Video…? What Write Speed do we have to use?
Thanks for anyone that can help out!

Johnathon
Johnathon
May 17, 2020 5:46 PM
Reply to  William Quade

Can I show you my work? Maybe you can tell if anything is off??

Johnathon
Johnathon
May 17, 2020 6:10 PM
Reply to  William Quade

Uploading now….

Johnathon
Johnathon
May 17, 2020 6:12 PM
Reply to  William Quade

https://imgur.com/a/IbEDJhN Clear look at my work lol.

Johnathon
Johnathon
May 17, 2020 7:16 PM
Reply to  William Quade

@ William Quade Adjusting PS1 Laser “clock wise” helps the laser surpass the oem set omhs. This might help your other customers out that aren’t able to load up Burned CD Disc! I can make/post a photo of the “How-To” if you needed to know.

Johnathon
Johnathon
May 17, 2020 7:20 PM
Reply to  William Quade

FYI First time I ever soldered.. I have flux pen and paste, Its hard for me to flow solder in the tight spots.. Not as easy so i thought…. I am using 700F on the solder pen. Tinning the wire and board points, then using flux pen before i take the wire in the board… That how its done? lmao

Johnathon
Johnathon
May 17, 2020 5:44 PM

System having a hard time playing “Back up’s”! *PU-23 Soldered all 7 wires (short) MM3 modchip USA
The chip does let the PS1 load the back up now, just not as smooth as I seem people posting videos about it….
*whats the Write speed for PS1 games…Thank you all!

Johnathon
Johnathon
May 18, 2020 12:15 AM

To all: I can say I burned up 20 Blank Vervatim 700mb CD-R’s With only success at Lower Burn speeds! anything over x8 and the PS1 Cannot decode the data, guessing do to the speed the drive can read at…which is can’t seem to find a true Read speed for the 9001 model Drive… Thanks to the Site owner! much help and fast response is Awesome! Will buy more for this seller!

Bill S
Bill S
May 18, 2020 7:33 PM

Noob here, please forgive me lol

so I screwed up pretty bad around #3. the bottom 2 capacitors fell off along with the solder pads, and I managed to lose one of them 😑

Do you know what this capacitor is called? I want to verify that it is included in this replacement surface capacitor pack

Also debating just sending it in to you lol – if I do that would you happen to have the spare capacitors on hand?

Shynryu
June 12, 2020 6:55 PM

Thank you so much for these guides

20200612_165034~4.jpg
Brent
Brent
June 29, 2020 11:55 AM

I cannot comment on the functionality of the chip since I pretty much destroyed my board after bridging some legs on the tiny chip by wire 3. Tried and tried to remove the solder, but no luck. I guess the moral of the story is if you think you can do this, you most likely can’t. If you know you can, then good luck. Make sure you have the right tools and a good, well lit workspace with a microscope. I’ve modded systems in the past, but this was somehow the most challenging (for me) mod I’ve attempted and failed… Read more »

Mike
Mike
July 17, 2020 4:51 AM

Gud day do you have a wiring connection for this kind of modchip? for pu23 board, thanks

IMG_20200717_174813.jpg
Flavio
Flavio
July 28, 2020 2:30 PM

Can’t make it work on pu23 scph 9002. I buyed a modchip in China, seller confirm that the chip is programed but can’t make it work. Tried the mm3 diagram, the old one diagram only with 3 wires soldered and my last try is the mayumi diagram with pin 2 also soldered. I follow all the steps like no big wires and check all my points, no bridges. I suspect my modchip is not programmed because I try all diagrams. At this moment my console loads original media but can’t load the backups.sometimes goes to music menu but most of… Read more »

Last edited 4 months ago by Flavio
Subsonix
September 4, 2020 6:45 AM

What’s the best way to strip chip wire? Can you get wire strippers that go down to such a small size (0.25mm)? Can i take a lighter the end of the wire to burn off the plastic or is that a big no no? Thank you

Subsonix
September 11, 2020 9:39 AM
Reply to  William Quade

Thank you for the help, i’m about to mod my 1st ps1. Hope it goes well

Patrick
Patrick
September 8, 2020 9:48 PM

Greetings! I tried installing the MM3 mod chip on my 9001 tonight. Once finished the power LED will come on, but the disc wont spin and no image is recognized by the TV.

Patrick
Patrick
September 9, 2020 12:46 PM
Reply to  William Quade

gotcha. Can I email you a picture of my board with the chip installed? See where I went wrong

Mr_Old_Skewl
Mr_Old_Skewl
September 22, 2020 5:06 PM

Here is one that I just did for Ebay. I used the installation guide from Gamefreax.de though. Their guides work with full stealth so I don’t usually deviate from them. (Not real confident about pulling pin 4 high…I’m pretty sure the code needs it for stealth to work.)

Mr_Old_Skewl
Mr_Old_Skewl
September 24, 2020 5:27 PM
Reply to  Mr_Old_Skewl

Not sure why that didn’t upload…

9001.png
Kurt
Kurt
November 2, 2020 5:21 PM

During the installation I lost the resistor for pin 3, do you know of anywhere to get it or am I sol

Noah
Noah
November 2, 2020 9:10 PM

Would I have to soder pin 4

Last edited 26 days ago by Noah
Noah
Noah
November 2, 2020 9:12 PM

I Cant find were pin 4 would go

Noah
Noah
November 5, 2020 8:43 PM
Reply to  William Quade

ok

Noah
Noah
November 13, 2020 10:45 PM

all my pins are right but putting in a backup said please insert PlayStation rom every thing is right what could be wrong

Noah
Noah
November 14, 2020 8:21 AM
Reply to  William Quade

i got this to work once today but the PlayStation logo came up but it would not load

Noah
Noah
November 14, 2020 10:31 AM
Reply to  William Quade

alight

Noah
Noah
November 14, 2020 12:12 PM
Reply to  William Quade

my disc was dirty do it did not read