troubleshooting a (mostly) broken laptop key

November 3, 2009 9:23 PM

My Thinkpad's n key doesn't work most of the time (but does work sometimes if I hit it in the right spot/from the right angle and hold for a bit)...what troubleshooting/fixes can I try before I give in and replace the whole keyboard?

Additional details:
1) I have already pried the keycap off and looked to see if anything was stuck under it (no)
2) this does not seem to be the result of spilled liquid (I have spilled stuff before, but nothing recently)
3) no need for workarounds or advice about how cheap/easy it is to replace Thinkpad keyboards - I've done it before, and will again if needed. That seems silly, though--the circuitry must be intact since it does work sometimes.

posted by needs more cowbell to computers & internet (8 comments total)

I know you said you checked to see if anything was stuck under the key, but my period key was acting the same way a while back and I don't think it was immediately obvious there was something stuck. There was a little bit of crumb or something stuck under the white thing that is sorta a hinged thing (I don't know what it's called)... I doubt it's that since you already checked, but just in case.
posted by tweedle at 9:33 PM on November 3

Okay, I should add that when I take the keycap off and hit the rubber/silicoe "nipple" underneath, I have the same issue getting an n to show up. (and I tried comparing this with how easily an M shows up when I take the M keycap off and hit the nipple under it--the M shows up easily, the n does not.) This has gotta mean it's not something stuck under the keycap.
posted by needs more cowbell at 9:46 PM on November 3

if you can get under the nipple to the contact try cleaning it off with isopropyl alcohol and or pencil eraser. sometime the nipple itself has become misaligned or creased so its not properly or entirely hitting the contact. goodluck.
posted by headless at 10:03 PM on November 3

How do I get under the nipple? On my laptop the white springy pieces kind of block access to the nipple. Can I take those white things off without breaking them?

Also: I have an entire identical keyboard around if that can help me in any way. A few of the keys don't work because coffee was spilled on it while the laptop was on and circuits were fried (or whatever it is that happens), but the parts are OK otherwise.
posted by needs more cowbell at 10:10 PM on November 3

2nding headless on cleaning the keyboard (which may not be enough; particularly with laptops, it's often heavy wear which has caused the conductive surface on the rubber mat to wear away).

Since you've got an identical keyboard to play with: Generally with laptop keyboards, there's no circuitry on the keyboard to fry - the keyboard's just a switch matrix; all the circuitry is on the m'board. So try pulling that one apart and cleaning it - at the very least, it'll be a practice run for the real thing.

IIRC the Thinkpads - at least, the old ones - are pretty easy to repair, because the keytop mechanisms are all connected to the upper frame. When you pull them apart, you end up with 4 basic parts - a frame which holds the keys, a silicone membrane with conductive pads, an insulating sheet, and the circuit board itself. The whole lot is sandwiched together & held by a bunch of 00 Philips head screws from the circuit board side - undo the screws, and it comes apart. Clean the circuit board contacts for each key with a soft eraser (I use microscrub & freon myself, but that's impossible to come by nowdays & hardly hardly eco-friendly ;-), rinse with distilled water, rinse again with isopropyl alcohol, and set aside to dry for a couple of days. Rinse the underside of the silicone membrane with distilled water (I wouldn't use alcohol here, it's a bit too much of a solvent), gently wipe with a wet soft sponge or cloth, and set aside to dry.

Now, the underside of the dimples in the silicone membrane have a conductive layer applied to them - it's usually carbon, which can be hard to see on the black/grey membrane, but it's there. This is what makes the contact when you press the key, and it's also what wears away with use. With your spare keyboard, it's probable those bits just have an insulating coating of dried coffee on them, and washing will be enough. With your hard / intermittent 'N' key, it's likely the coating has worn. You can buy carbon-loaded paint for repairing keyboards, or you can use silver-loaded paint meant for repairing circuit boards & window demisters - just paint it thinly on the bottom of the dimple associate with the difficult key, let dry, and re-assemble.

Personally, I can never get the proper carbon paint when I need it, and I think the silver-loaded paint is a bit thick for this purpose. I've had success using carbon paper - proper, old-fashioned black carbon paper, not the ink-transfer stuff - and burnishing carbon onto the bottom of the dimple. But that too is hard to come by these days, so I'd suggest using the silver-loaded paint.
posted by Pinback at 11:13 PM on November 3

Also, if it turns out to be something under or with the nipple and you can't get a key off of your other keyboard, they sell individual keys on ebay. They give you the key, the nipple, and the scaffolding, so you just pop it in. It's like a few bucks.
posted by puckupdate at 3:22 AM on November 4

In case it's useful, pics of the guts under said keycap:
pic 1
pic 2

Is there any way to get under the contact to clean?

Pinback: I have an R61i (same keyboard as the T60)...are you talking about that kind? I'm not seeing a way to pull my old one apart like you describe - it seems to be put together in a way that prying the front from the metal back would ruin it. Here's a pic.

puckupdate, I'm not really sure how that would help - I have pried the key off successfully (and since posting last night, also the scaffolding...but I can reuse that, and it doesn't seem like the problem is with those things...am I misunderstanding something?
posted by needs more cowbell at 8:22 AM on November 4

Update: ordered a new keyboard on ebay for $18.61. My conclusion is that if pressing the nipple does not register a character, and there's no way to clean under the nipple that I can see, this is unfixable.

Thanks for the ideas though, guys.
posted by needs more cowbell at 6:01 PM on November 5