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IBM USB upgrade Add ϲomment

This page describes how to upgrade a PS/2 IBM Model-M keyboard to USB. I only tried this on the 84 key space-saver model, so things might not fit on other types of keyboards.

A better solution would be to use a client-side USB connector on the keyboard, so a regular cable can be used. Since I didn't have one of those connectors lying around, I decided to use the host-side plug from the converter.

You might break things while doing this and I might have made errors in this document, so try this at your own risk only!

click on the pictures for a larger view.

The IBM keyboard has a PS/2 interface, which is not available on most modern computers. to be able to use PS/2 keyboards with USB, offers nice and small converters. They have put some work in testing a lot of different brands and types of convertes, and these seem to do the job well.
Open the keyboard by releasing the two screws on the back. You need a 7/32" nut driver for this, or small pliers. Open the PS2/USB converter by cracking open the casing with a small screwdriver. Disconnect the keyboard from the controller PCB by gently pulling out the flatcables.

Desolder the PS/2 connector from both the keyboard and the converter. Using litz wire can make things easier.

Now connect the converter to the keyboard as shown on the photograph and diagram. These four wires replace the original curly PS/2 cable.

If you have the tools (multimeter), confirm if the wiring is actually corresponding to this drawing.

     Red:	VCC +5v
     Blue:	GND
     Yellow:	PS/2 Clock
     Green:	PS/2 Data
The PS2/USB converter fits nicely on the location of the IBM PS/2 connector that was removed earlier. With some creative soldering, it can be secured to the ground connector and 2 holes in the PCB to hold it in place.
Saw, cut or file a small piece of plastic to cover the hole and let the USB connector peek out of the original hole of the IBM connector on the back. Put the PCB back in place and close the keyboard.

If the soldering work is not strong enough to hold the converter in place, glueing the plastic cover to the keyboard housing can provide extra support. This will make it hard to remove the PCB in the future, though.

here's another photoshoot of a Model-M being upgraded by Chris Lee

On Fri Mar 6 08:10:32 CET 2009, Greg wrote:
Can you tell me if this solution plays nicely with a KVM switch? Thank you!
On Fri May 1 13:49:46 CEST 2009, wrote:
thanks. good work.
On Wed Aug 4 02:49:00 CEST 2010, Pat wrote:
Is it possible to convert an RJ45 version of a type M to PS/2 or USB? Thank you.
On Mon Sep 6 22:50:46 CEST 2010, anonymous wrote:
take a closer look pat....he did remove the rj45 connector from the keyboard...most all of em we're rj45 on the keyboard side and ps/2 or AT on the host computer side of the could hot swap yer ps/2 keyboard with another model m on the spot cos of that rj45 cable....god i miss those days...
On Fri Jan 7 14:23:16 CET 2011, Chris wrote:
Real nice hack. I just ordered another usb converter so I am going to try this on one of my type M's. My concern is the stability of the joint.
On Sat Jun 11 14:02:09 CEST 2011, Fenris wrote:
Can anyone verify if this hack will work?
On Thu Dec 1 10:57:05 CET 2011, anonymous wrote:
Absolutely no reason this hack wouldn't work
On Mon Dec 26 15:05:17 CET 2011, niko wrote:
I tried this with a 1993 ibm model m, using the shown usb converter of and it did not work. ok, the leds flash once while switching on the computer but the machine does not receive key commands on the login mask. i veryfied all conncects with a digit-multimeter. some has an idea what i can do now?
On Mon Mar 5 05:33:36 CET 2012, Retaxis wrote:
I did a very similar mod a few days ago, but I didn't have to open the keyboard housing (which is half impossible anyway). I lopped the DIN5 (AT) connector off of the original cable, and soldered it onto the board for a cheap PS/2f to USBm converter. This adapter is cheap, and very available. It's the one with all the connectors on wires (PS/2 Mouse, PS/2 Keyboard and The USB connector), and a small box in between. It was a very simple conversion, I traced the wires from the USB PCB to the PS/2 Keyboard connector, then through a PS/2 to DIN5 AT adapter with a multimeter, and soldered the leads directly to the PCB. After hacking both PS/2 connectors off, there's plenty of room in the original cheapo shell for the larger original cable. After testing, I glued the shell closed. It works great, unless you want to game with it (it has multiple-simultaneous-key-holding-down issues). It also makes it plug and play. As to the extra current required, that may be right, it doesn't always wake back up on the
On Mon Mar 5 05:35:48 CET 2012, Retaxis wrote:
As to the extra current required, that may be right, it doesn't always wake back up on the notebook USB, but on the powered hub, it's the old faithful I expect from a Model M. If you can't bear to part up an original cable, you can order the original connector online. It isn't an RJ-11 or RJ-45, it is called an SDL connector.
On Sat Jul 21 07:06:18 CEST 2012, wrote:
Can I also do this with a Northgate Omnikey 102 keyboard?