#5658 NORM Ship.2: Sticky Alt or Control Key

[Zarro Boogs per Child]

#5658: Sticky Alt or Control Key
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  Reporter:  davidpfarrell  |       Owner:  wad      
      Type:  defect         |      Status:  new      
  Priority:  normal         |   Milestone:  Ship.2   
 Component:  hardware       |     Version:  Build 650
Resolution:                 |    Keywords:           
  Verified:  0              |    Blocking:           
 Blockedby:                 |  
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Comment(by legutierr):

 Replying to [comment:41 joemck]:
 > It is indeed a hardware problem.  It seems that part of the frame around
 the keyboard presses down and inward on the edge of the rubber membrane.
 I took apart the bottom part of my XO, reassembled it, and the problem was
 still there.  Then I took it apart again, ran the OFW keyboard diagnostic
 with it open, messed with the edge of the frame, saw that it's what's
 causing the problem, then started putting it back together to see what
 part made it start messing up when I put it in.  I got the whole thing
 back together without any stuck keys, so I'm not entirely sure exactly
 what part was causing the problem.
 >
 > If you have stuck-key problems, I suggest pressing the thin left edge of
 the white keyboard frame outward into the green rail.

 I think it's quite possible that joemck is correct.  After having
 experiencing a temporary respite from this problem, my alt and ctrl keys
 started sticking again, as bad as or worse than before.

 Just now I ran the diagnostic, though.  Although the alt and ctrl keys
 weren't stuck when it came on, as soon as I touched them they stuck, and
 there was no way to unstick them.  I then peeled the rubber back on the
 left side, and the stuck keys *immediately* became unstuck.  Touching the
 circuit-board directly caused those keys to appear as pressed, but they
 did not stick after releasing pressure.  It seems like the rubber was
 being squeezed down by the hard-plastic encasing, causing the keys to
 stick.

 I'll take the thing apart tomorrow and put it back together, making sure
 that there is no pressure on the keyboard by the rubber.

 It seems that this kind of squeezing of the rubber by the plastic encasing
 could well explain the alt and ctrl keys sticking, as they are located at
 the edge of the board.  It also explains why jiggling the keys can cause
 them to unstick, and why near-by keys can influence the sticking behavior.
 Temperature may also affect the tensions on the materials
 (expand/contract), which could explain some of the variability.  But could
 pressure from the encasing also cause other mid-keyboard keys to stick?  I
 think I read that someone was experiencing sticking of letter keys (am I
 wrong about that? can anyone confirm that the sticking problem is with any
 but the keys at the edge?).  If it is only edge keys that are affected,
 then it may be tight screws that are causing the problem and not moisture.

 It is quite possible, however, that there can be multiple causes inducing
 the same symptoms in different cases, or that one cause contributes to or
 worsens the impact of another cause.  Humidity could be the only factor in
 some cases, or could cause mechanical problems to emerge that wouldn't
 otherwise.  Or moisture might have nothing to do with it.

 Can anyone think of any tests that could confirm or exclude either cause
 definitively?  Maybe if water were poured over the exposed keyboard
 circutboard (rubber pulled back), and it continued to function in response
 to pressure, that would strongly tend to exclude the moisture hypothesis.
 Anyone want to do that to their laptop? (I don't.)  Regarding the pressure
 issue, tightening and loosening the screws would probably have an
 immediate and visible effect, if pressure were the cause of this problem.

-- 
Ticket URL: <http://dev.laptop.org/ticket/5658#comment:44>
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