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Author Topic: First IBM Model M, sometimes keys won't register  (Read 8928 times)

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Offline Cyberpunk

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First IBM Model M, sometimes keys won't register
« on: Sat, 19 January 2013, 13:49:38 »
Hi, so I'm currently typing with my Model M. Sometimes, some keys (like B, N, space bar...) won't register unless I press hard on them and after that they work fine for a while  :confused:...It sucks because the keyboard is in very good condition, I took it apart for cleaning using this site http://www.preater.com/modelm/ and nothing seemed broken. I would really love to save that bad boy!

edit: It's a model 42H1295 with the PS/2 cord soldered to the PCB inside the keyboard.
« Last Edit: Sat, 19 January 2013, 13:53:56 by Cyberpunk »
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Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #1 on: Sat, 19 January 2013, 15:14:39 »
Could it be that the key(s) is stuck with some dirt or the spring is bad?
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Offline tp4tissue

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Re: First IBM Model M, sometimes keys won't register
« Reply #2 on: Sat, 19 January 2013, 16:12:34 »
Clean the membrane
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Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #3 on: Sat, 19 January 2013, 17:51:27 »
Quote from: tp4tissue on Sat, 19 January 2013, 16:12:34
Clean the membrane

I would have to do the bolt mod? If yes, the only DIY I found was in the archive and missed pictures, do you have one to recommend following?
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Offline fohat.digs

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Re: First IBM Model M, sometimes keys won't register
« Reply #4 on: Sat, 19 January 2013, 18:31:58 »
Sandy has the quintessential guide, but forget the chisel and get a chisel-tip insert for your Xacto knife. And a soldering iron is best for making a divot to guide your drill bit.

http://wiki.geekhack.org/index.php?title=Modifications:IBM_Model_M:Nut_and_Bolt_Mod

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Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #5 on: Sat, 19 January 2013, 22:04:50 »
Quote from: fohat.digs on Sat, 19 January 2013, 18:31:58
Sandy has the quintessential guide, but forget the chisel and get a chisel-tip insert for your Xacto knife. And a soldering iron is best for making a divot to guide your drill bit.

http://wiki.geekhack.org/index.php?title=Modifications:IBM_Model_M:Nut_and_Bolt_Mod

Thank you! Ordered  the parts from McMaster-Carr, will keep this thread updated!
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Offline ch_123

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Re: First IBM Model M, sometimes keys won't register
« Reply #6 on: Tue, 22 January 2013, 14:53:25 »
If the membrane has a fried trace (it happens) you can fix it with one of these (or something similar)

http://www.ebay.com/itm/1x-Conductive-Silver-Writer-Conductive-Silver-ink-Pen-998-/181059135607?pt=LH_DefaultDomain_0&hash=item2a27f72877
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Offline rknize

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Re: First IBM Model M, sometimes keys won't register
« Reply #7 on: Tue, 22 January 2013, 14:56:58 »
If I were to guess, it sounds like you have some broken rivets in that area.
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Russ

Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #8 on: Tue, 29 January 2013, 17:33:41 »
Quote from: ch_123 on Tue, 22 January 2013, 14:53:25
If the membrane has a fried trace (it happens) you can fix it with one of these (or something similar)

http://www.ebay.com/itm/1x-Conductive-Silver-Writer-Conductive-Silver-ink-Pen-998-/181059135607?pt=LH_DefaultDomain_0&hash=item2a27f72877

Look at the outer trace, is it fried? On the other side all the traces are fine.

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Offline rootwyrm

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Re: First IBM Model M, sometimes keys won't register
« Reply #9 on: Tue, 29 January 2013, 17:41:10 »
Ouch. Some discoloration is perfectly normal, but that looks pretty much hosed, there. Impossible to say without testing. Simple method is to take a multimeter, set it to continuity mode, and test at contact points. But it looks burnt to my eyes.
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"I remain convinced I am the only person alive who has successfully worn out an IBM Model M mechanically."
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Offline tp4tissue

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Re: First IBM Model M, sometimes keys won't register
« Reply #10 on: Tue, 29 January 2013, 17:42:18 »
I've had traces that "looked" like that but weren't fried, but then 'others' were. Check with multimeter.
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Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #11 on: Tue, 29 January 2013, 17:47:37 »
I tried most of them with a multimeter and they were all working.
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Offline rootwyrm

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Re: First IBM Model M, sometimes keys won't register
« Reply #12 on: Tue, 29 January 2013, 18:54:46 »
Quote from: Cyberpunk on Tue, 29 January 2013, 17:47:37
I tried most of them with a multimeter and they were all working.

Okay, so there's two tests to do with the multimeter. The first is continuity - that's the 'quick' test that tells you whether or not the line is completely broken. Unfortunately, continuity is not the last word. Next step would be to do resistance test - obviously on lowest available setting. Sometimes lines will pass continuity but fail resistance. Still a reasonably quick one but takes a bit more time. You'll want to start with a known good line to get your baseline.

Given the description of the problem though, I doubt there's any real problems with the matrix. (Which by the way, you can order new from Unicomp if needed.) Most likely the backplate or barrel plate has a deformation. Which bolt modding may or may not fix. One of these days I should look into the costs for a run of heavy duty backplates to solve these issues - we have a number of local stamping facilities. (And it has to be a stamped part due to the curve.)
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"I remain convinced I am the only person alive who has successfully worn out an IBM Model M mechanically."
Daily Drivers: Adesso 625 (NPKC PBT / Kailh Blue), Rosewill RK9000V2 (KC PBT / MX Brown), 1994 Model M13, Sun Type4, and the rare IBM 1394540.

Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #13 on: Thu, 14 March 2013, 12:23:16 »
So I received all the parts I need to do the bolt mod, now I just want to be sure what holes needs to be drilled. Everywhere where there was a stud minus the bottom row?

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Offline rknize

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Re: First IBM Model M, sometimes keys won't register
« Reply #14 on: Thu, 14 March 2013, 13:11:32 »
You need to do the bottom row as well, though the diameter may be different depending on what you plan to do with those.
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Russ

Offline Cyberpunk

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Re: First IBM Model M, sometimes keys won't register
« Reply #15 on: Fri, 15 March 2013, 19:56:08 »
All right, so I drilled every holes now I'm ready to reassemble the parts but it was disassembled for weeks/months and now I don't remember what's the order for the plastic membranes. In order from the backplate: backplate, rubber mat, ?, ?, barrel plate. Gosh I feel stupid now ;P!

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Offline mich

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Re: First IBM Model M, sometimes keys won't register
« Reply #16 on: Sun, 17 March 2013, 06:18:41 »
Quote from: Cyberpunk on Fri, 15 March 2013, 19:56:08
All right, so I drilled every holes now I'm ready to reassemble the parts but it was disassembled for weeks/months and now I don't remember what's the order for the plastic membranes. In order from the backplate: backplate, rubber mat, ?, ?, barrel plate. Gosh I feel stupid now ;P!
That's absolutely obvious. Membrane traces have to touch each other through holes, so the order is:

Steel plate.
Membrane with traces on upper side.
Membrane with holes.
Membrane with traces on bottom side.
Rubber mat.
Hammers.
Barrels.
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