PU-22 Mayumi v4 modchip installation diagram

This is my favorite version of the PlayStation 1. It’s in newer systems, so the lasers are more likely to still be in good condition, but the system still has both the serial and parallel ports on the back. This board was used primarily with the SCPH-7500 series of systems.

For more information about Mayumi v4 chips click here, for more information about PS1 modchips click here.

PU-22 Mayumi v4 modchip installation diagram

MM3 chip pinout

 

PU-22 Mayumi v4 diagram

Above is the diagram for the PU-22. Pin four is located towards the top left side of the board.

This diagram is fairly straightforward. There aren’t really any tricky points, or surface mount components you need to solder to.

Installation tips

Here are some tips I have for you when you are soldering your chip into the PU-22.

  • Cut your wires to be as short and direct as possible.
  • The high speed clock line (pin 2) needs to be especially short and carefully routed.
  • 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.
  • Watch out for solder splatter when you are desoldering the metal shield on top of the board.
  • Placing the chip where the pin seven circle is seems to be the ideal location.

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)

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.

  • William Quade (me)

Subscribe
Notify of
guest
11 Comments
Most Voted
Newest Oldest
Inline Feedbacks
View all comments
Chien
Chien
April 16, 2019 12:48 AM

I keep forgetting to post a pic of my install. Any tips for improvement?

https://imgur.com/EYMRz1b

Kimbapslice
Kimbapslice
June 7, 2019 6:51 AM

I used your diagram to successfully wire up a SCPH-7501 PU-22. I should have taken a picture before putting on the metal shielding. I wired pin 2 of the chip directly to the motherboard. I did not connect pin 4 to pin 1, just to the regular pin 4 location.

Reaver
Reaver
June 15, 2019 3:55 PM

Is There An Alternate Point for Wire 6 ? I Have Accidentally Removed The Solder Pad to That Point.

Reaver
Reaver
June 19, 2019 12:03 PM
Reply to  William Quade

Thank You. I Was Able To Solder It to The Nearest Capacitor Along That Trace Instead and It Works Great.

Jon Nielsen
Jon Nielsen
August 30, 2020 12:17 PM

I also used this guide – cheers. The PU-22 was my backup PlayStation bought in case the other (a PU-18 model) mod failed. The previous owner had installed another modchip in it that I removed. But the pin 5 joint wasn’t too happy about being touched again, so the entire trace came off with the wire. Attached picture shows how I got around this.

IMG_20200829_153523__01.png
Last edited 2 months ago by Jon Nielsen
Dani
Dani
September 8, 2020 7:26 AM
Reply to  Jon Nielsen

Same thing happened to me. Desoldered pad 5(only the round pad) from the motherboard after removing old solder…… Isn’t there a way to remake a solder pad or to make the solder to stick again on the motherboard? I’m in no way able to solder the wire directly to the pin of the Sony chip…..

Dani
Dani
September 8, 2020 11:50 AM
Reply to  William Quade

Damn…. Thank you.

Jon Nielsen
Jon Nielsen
September 8, 2020 12:53 PM
Reply to  Dani

I did it because I had little other choice. Not saying it was easy, or that I thought today was the day to try something I’ve only seen done by the YouTube solder-pornographers:D In my case the length of the trace just peeled off when exposed to heat. Figured connection to chip was my best bet. I fixed the wire between the caps using double sided tape. Added flux around chip pin that the trace ended at, tinned the wire, nudging back and forward, checking with magnifying glass (couldn’t see directly), then touched (!) it with tinned soldering iron when… Read more »