Keys dying in my XOs

[James Cameron]

On Wed, Nov 25, 2015 at 08:32:49PM -0500, Sebastian Silva wrote:
> On 25/11/15 20:02, James Cameron wrote:
> > We continue to make the keyboards, so I'm interested in any wide
> > area systemic report, so that I can feed it back into
> > manufacturing.
> >
> > The array of key switches may be connected in a matrix.  A key
> > switch that does not release can cause several keys to stop
> > working.
> 
> On my XO1.5 that I got from the peruvian deployment (from the
> Ministry of Education), I tested this, and have found there are two
> "columns" of keys that don't respond:
> 
> F1, 2, w, s, x, <>
> and
> F8, 8, i, k, ;
> 
> It has latinamerican/spanish keyboard.  The right shift key
> sometimes appears stuck. It is not responding now.

Thanks for the reply.

These keys not responding suggest either;

- a broken column circuit in the printed circuit underneath the keys,
  e.g. due to impact, corrosion, or latent defect,

- a broken column circuit in the flexible circuit connector, e.g. due
  to thermal cycles over a long life, or foreign substances, or

- damaged keyboard controller chip, due to electrostatic discharge
  carried from fingers.

What you might do;

- disassemble the bottom,
  http://wiki.laptop.org/go/Disassembly_bottom

- expose the flexible circuit connectors,

- look for mold, fungi, sugar, coffee, or other signs of invasion,

- unclip each cable, clean the connector surface with isopropyl
  alcohol swab, allow to dry, and reclip,

- test before full reassembly.

Given the age of the laptop, there is a risk of breaking the retaining
lever on the connectors.

> However when within the OS, I'm sure there were other keys as I
> couldn't type "l" or "g" keys.

Hmm.  Then it is also possible that key switches are not releasing.

> 
> On the XO4 I couldn't figure out how to reach the keyboard self test.
> "menu" command in ofw triggers an OS boot selector (linux/android)
> instead of the test.

That's odd.  It doesn't happen if I type "menu".  Q7C05.

Either type "test /keyboard" or use the left rocker key on boot to
enter the self test menu.

> If it helps I believe this may have to do with the fact that we just
> moved to the rainforest and have experienced very high temperatures
> (up to 40 C) for the past six months.

Perfect growing conditions.  ;-)

> I can inquire if more people have found this issue at the ministry
> if you like.

I remember now a deployment report that counted the number of
keyboards replaced due to wear.  It was a reasonable percentage, and
seemed to follow a statistical normal distribution over time.

I think there's risk of distorting the statistics if we ask, so I'm
quite willing to hear of statistics but not go look for them.

-- 
James Cameron
http://quozl.netrek.org/