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
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.
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:
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 »
I’ll make a better diagram this weekend and get back to you when it’s ready.
One thing to keep in mind is that the area in the diagram in between the labels for 1, 8, 3, 6, and 5 is electrically noisy and can cause problems with modchips. So if you placed your chip in that area, or ran most of your wires over that area, it could cause problems.
Hello,
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!
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.
Pin 6 connects to the leg of that chip. If you broke the leg then there probably isn’t any easy way to get it working again (especially since it’s not reading discs). You’ll probably want to try another board.
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?
Thanks.
No. It’s some other chip. Definitely not a MM3.
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?
Thanks.
You can connect pin 4 on the chip to the same place as pin 1. Don’t connect pin 4 on the board to anything though.
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.
You’re probably just better off following the diagram exactly then. Connect pin 4 to where it is in the diagram. Connect pin 1 to where it is in the diagram.
ok, i try to follow the diagram.
Thank you so much.
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.
If you’re just having issues with backups it’s an issue with a worn out laser (since backups are harder to read).
Bought an MM3 chip off you that arrived a few days ago. I’m not the best at soldering, and this particular install seemed daunting. But, I just installed it this morning on a 7001, took under 30 minutes from beginning to end (tear down and putting it back together included). Reads legit discs, pressed copied discs (discs that still required a modchip to even run), but doesn’t read any burnt CD-R. I’m chalking that up to being a weak laser.
All-in-all, I’d call the installation a success! Thanks for the guide!
Install pic here: https://imgur.com/a/HuZJ5hL
pu-20 board with mm3 chip is installed and working, thank you for taking the time to post these diagrams, incase anyone else runs into this issue, at first after install it would play normal games but backups would freeze/ fmv would be a stuttery mess, ended up following a guide to increase the laser intensity with the trim pot located on the back of the laser assembly and it now plays backups with no issue, ADJUST THE LASER AT YOUR OWN RISK and please follow a guide if you attempt the adjustment yourself, as too far can apparently burn out… Read more »
Still having issues. i have a japanese pu-20 board. DIsk reads perfect without modchip installed. When installed it reads japanese games as cd and doesnt even try with us games. Ive double checked my solder points and no bridges aswell. Could use some help.
Japanese systems starting with some of the SCPH-3000 models had additional region locking in the BIOS that prevents non Japanese region games from playing, even with a modchip. That’s why US games aren’t working.
Are you sure you have an MM3 programmed for a Japanese system?
Thankyou for the update. I’ll try again with another console. Thanks William
Hi William. I tried to install a mm3 onto my pu-20 and ran into a snag, (the power leg on the mm3 snapped off the chip >.> ) Once I removed the wires for the mm3 the pad lifted on “5”. The leg that connects to the 118 742 chip is still intact but my consoles no longer reading any discs. Seeing as the pad didn’t go anywhere I thought it was just a test pad for the chip. So do you know what this leg on chip 118 742 does? And if I get another mm3 and solder it… Read more »
The pad is just a test pad and connects to pin 10 on that chip (see 9 and 16 pins are labeled on the board). If your system works you can solder to that leg and get it to read backups, but considering it’s not working at the moment something else is messed up on your board.
Okay, thanks for the prompt reply. I’ll get a magnifier out and see if I can see whats messed it up. Is that chip the one that deals with the copy protection?
Hey man, I followed your mod to the letter except pin 4 seemed too hard to connect, so I just connected it to pin 1 on the chip. Can you email me? I dont know why the mod isnt working, I used magic iso to make the bin cue file then iMgburn to make the backup disc (my ff7 disc is messed up…) but it only wants to go to the cd player screen.. What am I doing wrong? See pic