How do I open IBM Model M2?

[TapX]

Hello fellow mechanical keyboard enthusiasts.

Recently I got ahold of what appears to be an IBM Model M2 (got that from a reverse image search), with Part. No. 1399070, Manufactured by Lexmark in the UK. From the sound of it, I have deducted that it's a spring-type mechanical.





Thing is, that it doesn't work neither on my laptop, nor on a PC of its era (tried it on a Compaq Deskpro with Windows 98SE, for anyone wondering)

The only thing I get is this, those lights stuck on and nothing working.



Or just the three lights flashing for half a sec and then going completely dead. I presume that it's faulty wire or some short inside it. How do I open and fix it?

Thank you very much and I deeply apologise if this has been brought up before on a topic, and I couldn't find it.

[Muirium]

Well identified. You do indeed have an IBM Model M2.

http://deskthority.net/wiki/IBM_Model_M2

It was the final redesign of the venerable Model M that IBM / Lexmark produced. Buckling spring in all its clicky, springy glory! Here's one of those springs with the cap removed:



As for what's wrong with it, you're talking about a PS/2 plug, right?

[TapX]

Yes, I am indeed talking about a PS/2 plug. Already got an adapter too.

[Muirium]

PS/2's pretty simple, and Model Ms are pretty tough. I don't know what would be up with it. Bear in mind that PS/2 keyboard and mice sockets are incompatible (if you were using PCs back then, you'll know of course) and this also applies to adapters. Oh, and the M2 needs an active adapter. Most adapters are passive: they hook up to a dual-mode keyboard which does the USB work for them. The M2 is purely PS/2.

[TapX]

My adapter is this, passive, from the looks of it:



As to what's wrong with it, I don't know either, I just presume it is faulty wiring, as your wiki article states

The M2 is well known for electronics problems. The capacitors in the logic board are prone to failure, possibly due to IBM's use of early surface mount technology in the production of the controller board. Failure usually occurs after long periods of not being used. The usual method of diagnosing capacitor failure is that the Caps and Scroll Lock stay on whilst the keyboard doesn't respond to keypresses. However, there are guides to replacing the capacitors available which appear to solve these issues.

[Muirium]

Ah, of course. The M2 was notorious for leaky capacitors. I have a few Model Ms, but no M2, and despite their being older, that problem has never hit me. If you're having the same lights-but-no-action problem without the adapter, then it sounds like a good idea to delve inside.

(Your adapter is indeed probably no good, judging by its size. Definitely verify with a real PS/2 port.)

Model Ms are held together with some fairly deep recessed M5.5 hex nuts. My guess is the M2 is similar. Got the appropriate tools? Or even better: an M2 specific repair guide!

[kint]

Welcome to the forum.
Your adapter is exactly that, an adapter not a converter.
For a passive adapter to work, the keyboard controller in the board has to be able to speak PS/2 and USB protocol, because the adapter just rearranges wires.
The converter on the other hand translates PS/2 protocol to USB protocol, hence, being active, will support your keyboard (which is native PS/2 all the way) So get something like this:
http://www.amazon.co.uk/TWIN-ADAPTOR-CA ... 2_edpp_url
There's a controller inside translating PS/2 to USB - although most sites describe it wrongly as an adapter.
This might solve your problem, or replacing IBM's faulty capacitors. Regardless you won't know before you have the correct adaptor/converter.

Edit:

Whereas other buckling spring keyboards consisted of an barrel housing with attached metal backplate housed inside a plastic case, the M2 used a simple two-piece snap-together casing.

Edit2:
http://geekhack.org/index.php?topic=5065.0

[Broadmonkey]

I've got an M2. I Changed the capacitors without even checking if it worked first. I used a simple flathead screwdriver to take out the triangle (or was it square?) screws.

[TapX]

I have verified it with a real PS/2 port and I got the same problem. So, yeah, it's the capacitors. Do you have any idea on where to find a replacement and how to replace them?

[Muirium]

From Kint's link (which you might need a GH account to see):

These can dry up over time and stop working. After 18 years it is quite possible that they're dry. The solution is to replace them. The small one is 2.2uF 50v, the big one is 47uF 16v. I used these for replacement:

2.2uF 63v electrolytic
47uF 16v tantal

Tantal is better because it doesn't dry but I only had a 2.2uF 35v tantal and didn't want to do it twice if that wouldn't work.

I didn't remove the pcb from the case.

The SMD capacitors are difficult to desolder. I use a very hot temperature, add a little solder for better heat distribution and push the legs to the side. If you push against the capacitor it will finally come loose with a snap and tear the other circuit path off in the process. So pushing the leg to the side seems to be the way to go. Here are the new parts, using correct polarity:

Immediately after soldering in the capacitors I connected the board to the PC. All LEDs stayed off. Tapping on the membrane showed that characters were generated as well!

During re-assembly there will be more holes than buckling springs. So it's good to take a pic before removing the springs

http://geekhack.org/index.php?topic=5065.0

The enhanced repairability factor is a big M2 advantage. The older Ms put up more of a fight every step of the way. Especially re: bolt mods.

[Findecanor]

Yep. I've opened a few M2s. Two screws. Pull off all the keys, then open all the snaps, prying open the shell while you do it so they don't snap together again. You are bound to break a snap or two, but don't fuss too much over that - you will have enough snaps intact when you are done.
When you open it, some springs with their feet attached may fall out - that is almost impossible to avoid. Make sure that you don't lose them.

When you put it back together, it is best to do so upside down on blocks or the desk will push the springs back up.
Then, be very careful to make sure that the spring is pointing straight up when you put each key back on - or it may get bent and will have to be replaced.

[TapX]

So, I repaired the capacitors, and now that I hooked it up my DeskPro, it has its lights going on like a progress bar. Anyone know what that means?

[Muirium]

Beats me. I've never seen or even heard of that.

[Ascaii]

Are you sure you got them soldered in the right way around? Ive had the flashing lights one some old ones where the caps contacts were damaged.

[TapX]

I had someone else solder them, but they do seem soldered in right.

[lowpoly]

... but they do seem soldered in right.

You do realize it's a polarity issue?

[idollar]

Hi,

Today I have received my first model m2. 10 euros

I believe that controller does not work.

I have checked the matrix and it is correct.

I have replaced the capacitors and the LEDs light correctly now, but the keyboard does not respond to any key press.

Any idea ?

Thanks in advance

[Chyros]

IIRC he screws are on the INSIDE of the case so you need to take the caps off first. It's also got those weird square-head screws (because IBM could never use normal tools ).

[terrycherry]

Before you repaired the capacitors occur, you should check the "Caps Lock" and "Scroll Lock" are always lighting together when you plug the connector on PC. If these two light didn't lighting on, it could not to repair for other reason.
Take a look I created some repair details of M2 if your work was correct.

-How to fix the capacitor failure (situation for Caps and Scroll Lock are lighting on)

1. Replace two electrolytics:
(Small one)Replace 2.2uF 50v to 2.2uF 100V electrolytic(電解電容)
(Big one)Replace 47uF 16v to 47uF 16V tantal(鉭質電容)
2. Connect the USB to PS/2 converter into the keyboard(if occurs problem, plug usb out and try again)

Hi,

Today I have received my first model m2. 10 euros

I believe that controller does not work.

I have checked the matrix and it is correct.

I have replaced the capacitors and the LEDs light correctly now, but the keyboard does not respond to any key press.

Any idea ?

Thanks in advance