A Proper Fat PS2 Fan Mod

Posted on Oct 30, 2025

On one of my many escapades to the land of e-waste I picked up a rough looking “fat” model PS2: an SCPH-39001 with a GH-022 motherboard. I bought this to mod a network adapter with a SATA kit from Bitfunx and test load times of UDPBD, MMCE, and HD loading with neutrino and nhddl.

The unfortunate part is that this model is notoriously loud, so many opt to “fan-mod” them. To skip my ramblings around the existing mods and process to my find and see my solution click here.

Existing mods

The PS2 has a 2-pin micro JST connector that provides variable voltage (as low as 5v) to a 7v 60mm Nidec fan. This is a problem for running most PC common fan that run at 5v or 12v.

Commonly people will 3D print a bracket, install a Noctua fan, and provide voltage to the fan in some way or another. The tricky part is getting a suitable voltage that is only active when the PS2 is not in standby.

DIY

I found many blog posts and forum posts where people buy a 12v fan, splice it to the original connector and call it a day.

Modders that have done this have primarily reported success but some have voiced or even experienced overheating. I don’t like the idea of either undervolting or overvolting my whatever fan I used.

AliExpress

The AliExpress gods presented me with ready-made PS2 fan mod kit after buying that SATA mod kit and an PSxMemCard Gen2 (an sd2psx clone).

A Noctua fan mod kit from a company called Ticknot

This kit is theoretically perfect: it’s plug and play and has am OEM-looking injection molded plastic bracket.

To run their provided Noctua fan they have a “5v stabilzer” hidden behind some heatshrink. I don’t know what type of stabilzer they’re using. I didn’t purchase this because it looked like a fun project to DIY and I wasn’t sure I trusted their design or if their Noctua fan was genuine.

Buying bracket for your own DIY solution seems like a good option for an OEM look.

sync-on-luma

sync-on-luma made a video documenting his problems with his fan mod overheating due to insufficient fan voltage. He solved this buy tapping into the controller port’s power rail which provides more voltage than the fan headers.

A PS2 controller daughter board with power and ground points highlighted

I didn’t like this solution because he runs a wire accross the board to a power rail that has a fuse that was designed for the normal operation of two DualShock 2 controllers. If the fan runs at full blast and both controllers’ vibration motors are active I’m not sure that the fuse will hold.

My mod

Coming up with my solution involved looking at the schematics. If you look up your SKU “SCPH-XXXX service manual” or better yet the motherboard model number “GH-XXX service manual” (SCPH-39001 and GH-022 for me) on your search engine of choice you’ll find a wonderful PDF full of schematics and PCB layouts of your model of PS2. This allowed me to plan out my mod with a much better information.

The fan driver

The heart of the fan driver is an Op Amp of model number NJM2125F-TE2 and is easily found on Mouser.

The fan driver circuit for a fat PS2

I’m not an electrical engineer, but I’ve spent the past year learning hardware, so I look at this through the basics. We have 12v in, a FAN PWM signal (!!!) in, and the circuit outputs what’s labeled 8.5v but in practice is variable based on the PWM signal.

It might be tempting to tap into the 12v coming in from fuse PS005 but if you trace the rail to its source it comes from the “power board” which is always on. But I found a very interesting signal: PWM! See the following for Kay’s explanation.

Kay’s explanation

Works like this https://electronics.stackexchange.com/questions/349561/fan-pwm-driver-design-question

  • Turns the PWM signal into a variable voltage (I think)
  • sends that to the op amp
  • the op amp controls the output transistor Q415
  • the transistor restricts or allows current to flow to the fan, controlling its speed

But what about 12v?

I need to find a non-standby 12v power source since the fan driver’s source isn’t viable. sync-on-luma’s approach is a good starting point.

PS2 GH-022 motherboard schematic of the controller board’s connector with 8v power highlighted

What he essentially tapped into is what’s labelled CON_+8V which has a test point labelled JL424 which when located on the board it is only a little bit above the fan connector CN403 so he didn’t need to tap into the controller daugher board all along!

PS2 GH-022 motherboard schematic showing the 8v controller rail with a test point labelled JL424 PS2 GH-022 moterboard PCB design showing the power rails and fan driver

It’s good info that CON_+8V is a switched rail so if we trace back its 12v source we arrive at Q412 and Q409.

PS2 GH-022 motherboard schematics showing the 12v power rail switching circuitry

What I saw here is 12v coming in and a chip with two MOSFET symbols being triggered by SW12 and HDD_SW which come from the SysCon. The PS2 Dev Wiki’s page on the SysCon states that it handles power so I concluded SW12 must be the signal to switch on the main 12v power rail! See below for Kay’s explanation.

Kays explanation

This kind of circuit is called a High Side Drive. Power is interrupted to 12v switched by disconnecting the positive 12v line. This can be compared to a Low Side Drive, where power is interrupted by disconnecting the ground return path instead. High side drives are generally safer to use, but can be a bit more complicated to implement.

In our case, we cannot drive the Q412 MOSFET directly. In order to control power going through the MOSFET, we need to be able to control close to 12v on the gate pin. This is not possible using the SW12 pin on the SysCon IO because that only goes up to 3.3v. Instead, we pull the gate pin high to 12v and then use the transistor to pull it all the way to ground. This allows us to swing the voltage on the gate pin of the Q412 MOSFET between 0 and 12v, giving us control of it. The transistor is much more tolerant to being driven at low voltages in this configuration, so it can be controlled directly with the SysCon pin.

PS2 GH-022 motherboard schematic showing the 12v rail with a test point labelled JL411 PS2 GH-022 motherboard PCB design showing the location of JL411 with a red circle, arrow, and the text “12v” located near the fan connector

Following it to the right I find a test point labelled JL411 which when located on the board is very close by to JL424 (CON_+8V).

The plan and testing

Assuming that the JL411 is the switched 12v rail and FAN_PWM is suitable I had everything I need to run a standard 12v PC fan. So it was time to test.

Powering the PS2 in a way I would not recommend I probed FAN_PWM on resistor R474 and the 12v rail on JL411.

A stripped down PS2 laid out on a shelf with the power supply connected with alligator clips

An oscilloscope showing a PWM signal

The PWM signal looks good and the 12v rail turned on as expected so I hooked up a random 12v Noctua fan that was kicking around and the fan responded to the PWM signal like I wanted.

Dupont test leads soldered to a PS2 motherboard running to a fan

The “proper” way

To perform my fan mod you need a 4-wire 12v PC fan (I used a Noctua NF-A6x25), soldering equipment, a service manual (easily located online see My mod), and experience/confidence with a little micro-soldering.

Noctua fans come with an extension cable which I used to make the fan easily removable like the original. You need to hook up ground, 12v, and PWM. On Noctua fan’s these are black, yellow, and blue respectively.

A diagram showing the pinout of Noctua 12v fans

source

  1. Solder ground to any ground

There are multiple ground test pads to the left of the fan headers (CN403) and driver circuit labelled JL402, JL404, and JL406 respectively any of which will work. The fan’s original ground connection would work. When in doubt use a multimeter in continuity mode to test against a known ground.

  1. Solder 12v to the the test pad JL411 located up and to the left of the fan headers (CN403).

  2. Solder PWM to the side of the resistor R474 furthest from the IC with the thin trace running back to the SysCon.

A fan cable soldered to the appropriate points on a PS2’s motherboard

Route the fan cable, mount the fan to the bracket (3D-printed or otherwise), button up the PS2 and you’re done!

A PS2 fan-modded with a Noctua fan and 3D-printed bracket

Wrapping up

I was very pleased to come up with a mod that seems the most “proper”. My good friend Kay helped with double checking my understanding of the schematics and Pawprint Prototyping’s equipment made me confident to do this myself.

In the future I need to add a fuse on the 12v going to the fan to prevent potential damage.