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
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.
- 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.
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 »
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 »
You can actually directly boot game backup discs on the Dreamcast, no need for a chip.
There are also mods for the Dreamcast that allow you to boot game backups over something like an SD or CF card.
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
It could be that the laser is worn out, or it could be a bad installation (if the wires are too long, or run over noisy components they can pick up noise and make the system have problems booting). Send me a picture of your installation and I’ll let you know if that’s the problem.
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!
Can it still play genuine copies of games? If it can’t play audio CDs then that would mean that the laser is worn, and would be the reason why backups don’t work.
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?
You can send me an email: liam@quade.co
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
Could you post some links to pictures or your installation, or email them to me: liam@quade.co
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
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?
It’s an optional pin. It’s just in the original diagram to be complete.
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…
Pin 2 is for the clock line, and is only used for Mayumi chips. Pin 4 is used for the mode selection using the reset button, but isn’t needed because the MM3 supports every game already (some older chips had a disable mode so that games that had anti-modchip code could be played).
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.
Yes, because you still have the PU-23 main board from the SCPH-9001.
Thank you very much.
Installed yesterday, just needed a reminder on where pins 5-8 on the MM3 PIC were. Thanks.
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?
Pin 2 for the MM3 does nothing. Leaving it connected likely won’t cause any problems.
Pin 4 is used to switch between operating modes using the reset button, so leaving it connected is not a problem.
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 »
Elder Bog,
Not to jump in place of William. Try cutting your wires shorter.
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.
man i love you easy install with your picture much appreciated works flawlessly
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.
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 »
Are you sure the chip is an MM3? There were a lot of modchips that can use the 12C508A.
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
Yeah, that’s definitely not a MM3. It’s a classic 4 wire chip. You might be better off just getting a new modchip (the older chips don’t support anti-modchip games). Here’s a 4 wire diagram I have for the PU-23:
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.
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!
I replied to the email you sent.
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.
You probably messed something up and likely blew some of the onboard fuses. You can email me a picture of your install or link an image gallery here.
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
Shorten the wires to be as short as possible. Those wires are way too long.
Thank you, I will do so and report back once done! I appreciate your quick reply and help.
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!
Check the entire board for blown fuses, solder blobs/bridges, and things like that.
Just used this diagram and it works like a charm! First time soldering something like this too. Thanks for the help!
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!
There is no perfect write speed. It’s all about finding the correct combination of CD burner, write speed, and CD media for your particular console.
Can I show you my work? Maybe you can tell if anything is off??
Yeah. Post a link to a picture.
Uploading now….
https://imgur.com/a/IbEDJhN Clear look at my work lol.
Making some changes to your installation could improve the boot success rate. Most of the connections don’t seem to be very good (cold solder joints), reflowing them with flux would help. Most of the wires can be shortened quite a bit as well. I also recommend finding alternative VCC/GND pin 1/8 points closer to the chip.
@ 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.
Yeah, that’s needed in some cases. The key is to only make very small adjustments between tests, and that some lasers are just worn too much.
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
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!
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!
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?
They are 22 ohm 0603 size resistors. If you lifted the solder pads along with the components then chances are you wouldn’t be able to repair it yourself (you’d need to solder wires from legs on that nearby chip to the capacitor, and then to the vias on the other side). I’d likely be able to fix it, but you might be better off just getting a new board since these systems aren’t worth that much.
Thank you so much for these guides
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 »