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geekhack Community => Keyboards => Topic started by: intealls on Sun, 04 July 2010, 15:36:18

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 15:36:18

Hi guys! Having a really weird problem with an M2 and was hoping someone could point me in the right direction of fixing it.

Got myself an m2 cheap today, it works, no led failures or anything, but when I press quotation mark (or neighboring keys, :, P, {) followed by arrow down in quick succession, the keyboard sometimes generates an extra unwanted character. Sometimes it's a dash, sometimes it's a 4. I would imagine it generates other keystrokes as well.

So if I press " ' down ' down ' " etc I get a lot of unwanted characters. Num lock is also randomly turned off and on.

Could this be an indication of cap failure or something more serious? Given that the problem only appears when pressing keys in a specific area, could there be something wrong with the membrane?

Any ideas?

Title: Weird M2 problem
Post by: ch_123 on Sun, 04 July 2010, 15:41:38

I'd say it's a membrane problem.

The M2 is easy to disassemble, if you're lucky, it could be some dirt on the membrane or something.

Title: Weird M2 problem
Post by: TexasFlood on Sun, 04 July 2010, 15:43:42

Maybe needs a good cleaning (http://www.instructables.com/id/Clean-your-vintage-IBM-M2-clicky-keyboard/)?

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 15:46:03

Thanks for the reply, gonna tear it open now.

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 15:50:15

Quote from: TexasFlood;199417

Maybe needs a good cleaning (http://www.instructables.com/id/Clean-your-vintage-IBM-M2-clicky-keyboard/)?

Yeah :) I followed that guide before, didn't wanna risk breaking it though so I just removed the keycaps and soaked them in soap water (used a large and loud compressed-air thing to blow all the water out of the keys before putting them back). The thing was, the keyboard was actually in great condition. Almost no dust underneath the keys, I guess the owner covered it or something.

Title: Weird M2 problem
Post by: ch_123 on Sun, 04 July 2010, 15:52:01

Be careful removing the keys - the stabilizer bars on large keys are actually plastic parts molded on to the keycaps... if you don't watch what you're doing, you can break them easily.

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 15:59:09

Quote from: ch_123;199421

Be careful removing the keys - the stabilizer bars on large keys are actually plastic parts molded on to the keycaps... if you don't watch what you're doing, you can break them easily.

Thanks. Will keep that in mind.

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 16:46:25

This is weird. The membrane looks brand new, I can't see any gunk or anything. The 'mat' that was covering the membrane was sort of dirty though, and was not entirely flat against the membrane (around the ESC key). Could that be the cause of the error?

Title: Weird M2 problem
Post by: ch_123 on Sun, 04 July 2010, 16:49:38

I don't think it would have been the mat, although it is preferable to have it clean and flush against the membrane.

With the mat removed, try pressing on the contacts corresponding to the defective keys and see if it does the same thing.

Also, have a look at the controller board and see if you see anything odd.

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 16:56:07

Yeah, it does the same thing when pressing the contacts :( Not as much though.

Can I safely separate the membrane halves without breaking anything?

You were bang-on. I think it's most definitely a membrane problem. After banging the contacts a bit, I haven't seen a single dash or Num Lock error, also there seems to be less 'bounce' in the problematic keys. As if the membrane halves aren't far enough from each other or something.

Title: Weird M2 problem
Post by: Rajagra on Sun, 04 July 2010, 18:44:18

Might be worth wigging the membrane where it connects to the controller, to clean the contacts a bit. I had to do that to fix some keys not responding. I couldn't remove the controller to do the job properly, but wiggling it about got it done.

Title: Weird M2 problem
Post by: intealls on Sun, 04 July 2010, 18:45:01

Argh. Just reassembled the sucker and the problem is still there. I guess just wiggling the membrane around didn't help much.

Edit: Damn, that was about the only place I didn't jiggle it. I'll try it in the morning and report how it goes :)

Thanks for all your help!

Title: Weird M2 problem
Post by: intealls on Mon, 05 July 2010, 09:14:55

Yay! Wiggling around the controller appears to have solved the problem. I gave it a _good_ wiggle this time, and I haven't been able to reproduce the problem. Thanks alot!

Title: Weird M2 problem
Post by: microsoft windows on Mon, 05 July 2010, 09:55:21

Maybe the ribbon cable was loose and wiggling around the controller reseated it.

Title: Weird M2 problem
Post by: TexasFlood on Mon, 05 July 2010, 10:56:11

Sometimes reseating connectors after years will resolve issues. Over time, years, corrosion can make a connection fail that was tenuous to start with.  Or perhaps you dislodged a bit of old coke soaked cheeto was sitting on the board and shorting it out.