Overly sensitive switch model m

[camerongray]

Hi,

I just picked up my first ever model M (1991) and so far I love it!  I have however found one issue.  My 'J' key is far too sensitive to activate, I can activate it by simply tapping on the cap, way before it actually clicks.  What can cause this and how would I go about fixing it, ideally I would like to avoid taking the whole thing apart.

Thanks in advance,
Cameron

[dorkvader]

It can be caused my a mis-seated keycap to a broken spring, or other issues. At first, reseat the cap and if that doesn't fix it, inspect the spring for damage. You may have to replace the spring.

Worse-case is having to bolt-mod it, but there are a surprising number of fixes that dont require that.

[camerongray]

I have now tried reseating/swapping the keycap as well as swapping the spring, now the key is stuck on.

I  don't think I reattatched the spring fully - What is the  "chopstick method" and how do I do it as I can't find any clear instructions?

[dorkvader]

There used to be some pictures of the chopstick method. It was invented by sandy55 back in the early 2000s. He is also the originator of the nut and bolt mod. for model M's.

Basically, you can use a chopstick to separate the spring from the hammer, and also "screw" it back on to the hammer. If you dont have it fully seated, it may be stuck on.

Have you inspected the spring? With a pen or chopstick, you can press the spring forward and down to emulate the buckling action. I do this with my bolt modded M's before fully reassembling them to make sure the hammers are fully seated, but you can also use it to check that the springs are operating correctly. Just pull off two keycaps and push the spring down and a little forward to see if the hammer will rotate right.

I suspect the spring may not be fully seated. Can you pull off two keycaps and take a picture?

--
Also: welcome to geekhack!

---
Relevant chopstick information:
http://geekhack.org/index.php?topic=38915.msg757200#msg757200
http://geekhack.org/index.php?topic=5265.msg77378#msg77378 (good topic, sadly it's old so there are no pictures)
http://deskthority.net/keyboards-f2/ibm-key-does-not-click-any-more-t1063.html (some info from DT)

[sth]

let me know if your spring is damaged. i've got some extras laying around i'll send you.

[camerongray]

The spring looks to be okay to me (I swapped it for Pause/Break to be sure.  Not sure if this is an indication to the problem  but the key works absolutely fine if I fit the keycap backwards, it doesn't click but activates when pressed,  when turning it back the key gets stuck on again!

I also can't really take it apart since the place I bought it from provides a 30 day warranty but they have put a sticker to preserve this over one of the screw holes!

Thank you very much for your continued help!

[camerongray]

Just a quick progress update - I've been trying the chopstick method using a shaved down straw from a can of compressed air - The j key is now at the stage where it does work but still sticks unless you are really abrupt when you press it - It also seems to occasionally activate when using surrounding keys - I'll keep at it - *fingers crossed*

[camerongray]

Final update - I've sorted my 'J' key to an extent that I am satisfied for now.  I still don't know the source of the problem but the key now works to a satisfactory level.  I was able to use the spring that I swapped out of my space bar for not clicking (It seemed a bit rusty) but when used with the 'J' key it still does not click but does allow the key to be used.  With any other spring the key would either jam on or be extremely sensitive so the slightest vibration would set it off (almost as though the spring was too long!)

Still a bit annoying though, if anyone has any other ideas, please let me know!

Only other thing, some of the keys feel a little 'scratchy' as though they are scraping against the side of the bit containing the spring (Not sure what it's called).  Is there any way to rectify this, is it normal or does it just happen with age?

[rootwyrm]

Sigh. Afraid I have bad news.

The symptoms you're describing are most likely a failed hammer plate retainer or hammer. The problem is that the hammer is not returning to the 'rest' position. So it's always resting on the matrix in the 'on' position. The only repair for this problem is to replace the hammer or the entire barrel plate, if the retainer is the problem. It is not repairable without complete disassembly including bolt-modding.

Without actually separating the sections, it's impossible to tell if it's retainer or hammer failure. Neither seems to be more common than the other, so it's 50/50. With the key backwards, you're tilting the hammer enough to simulate resting position.

[camerongray]

I somehow seem to have fixed it!  In a last ditch attempt I swapped the dodgy spring I was using on 'J' with a completely fresh one from 'F1' and it works and feels just like all the other keys!  I now need to press F1 pretty hard but that's no big deal, could be an advantage since It'll be harder to accidentally open help pages!

I will now work on the "If it ain't broke don't fix it" principle and never remove the 'J' key again!

Thanks for all your help!

Cameron

[fohat.digs]

If you are handy with basic tools, such as chisels and drills (a Dremel or UK equivalent is much better since you will need to drill a bunch of tiny holes straight down) then a bolt modification (aka bolt-mod) is not too difficult and will allow you to totally clean and adjust your keyboard inside and out. Now and in the future.

Look for Sandy's bolt mod http://wiki.geekhack.org/index.php?title=Modifications:IBM_Model_M:Nut_and_Bolt_Mod and do that.

The first time it will take a few hours but is worth it. I have done several (perhaps 6-8) and it is "de rigueur" for serious Model M aficionados.

Send me a personal message if you need replacement parts, although it will cost a few pounds and take more than a week since I am in the US. Otherwise, scavenge a replacement hammer/spring from "Pause" or something and move on.

[fohat.digs]

unintentional duplicate post

[rootwyrm]

I somehow seem to have fixed it!  In a last ditch attempt I swapped the dodgy spring I was using on 'J' with a completely fresh one from 'F1' and it works and feels just like all the other keys!  I now need to press F1 pretty hard but that's no big deal, could be an advantage since It'll be harder to accidentally open help pages!

I will now work on the "If it ain't broke don't fix it" principle and never remove the 'J' key again!

Thanks for all your help!

Cameron

That's... weird.

Can you remove the spring from F1 again and post some pictures of it? The symptoms are without question hammer problem, so a spring swap shouldn't fix it. Hammer problems often result in no-click because the spring doesn't reach the buckling point - the hammer strikes well before then. I think possibly someone either caused physical damage to the spring or swapped in an incorrect spring. (I have never seen a broken spring without physical damage being involved.)

Wonder if somebody already repaired it and swapped in the wrong spring. Remember that the click comes from the spring reaching a specific compression point, at which point it buckles and collides with the barrel plate. If the spring compresses too quickly or is too long, it won't reach the buckling point but will still actuate the hammer. I should've thought of that first, but it's Friday. So I'm excused.

*facepalm*
Friday! I'm excused! I say so!
Pop the keycaps from F1, F2, J, and K. Then lift the top of the keyboard so it's tilted downward (F-row \ Spacebar <-- like this)
The springs should fall forward and all be the same height. Then tilt it the other way. Springs should all be centered and the same height.

[camerongray]

Hmm, I'd rather not touch it!  But they J and K seemed to align fine when tilting (I remember thinking it was odd that they did that fine yet J was still dodgy)

The spring under F1 is actually rusty and broken (No sign of liquid oddly and the rest of the springs are fine) - I removed it from the spacebar where the top coil or so was broken off and stuck to the inside of the key - It works under F1 though (May get a new spring at some point)

All I can think is that I wasn't fitting the new springs properly due to being new to the Model M and I just got lucky during my last attempt!

Anyway, thanks for all your help - Now I just need to get used to it, coming from MX Blues (Majestouch) it feels really heavy!

[rootwyrm]

Hmm, I'd rather not touch it!  But they J and K seemed to align fine when tilting (I remember thinking it was odd that they did that fine yet J was still dodgy)

The spring under F1 is actually rusty and broken (No sign of liquid oddly and the rest of the springs are fine) - I removed it from the spacebar where the top coil or so was broken off and stuck to the inside of the key - It works under F1 though (May get a new spring at some point)

All I can think is that I wasn't fitting the new springs properly due to being new to the Model M and I just got lucky during my last attempt!

Anyway, thanks for all your help - Now I just need to get used to it, coming from MX Blues (Majestouch) it feels really heavy!

Ah yeah. That would most definitely do it. And no surprise: physical damage, not actual spring failure. (Seriously. These springs just do not %@#&*ing break ever.)

Definitely replace that spring, and everything will be good as new. Because it's an M. ^^

[rknize]

Sometimes the little nub inside the key cap where the spring is supposed to seat has a burr that prevents the spring from popping into place when the cap is inserted.  Leaning the keyboard on its back while inserting the cap aims the spring to the right spot.  A sticky key or key that feels mushy or balky is often related to this.  Other causes might be a bit of debris under the hammer.  If you tilt the keyboard back and forth with the cap out, the spring should rock back an forth freely.