And now to something completely different ... when discussing the keyboard illumination of the N900 with Joerg, I commented that it left a lot to be desired. He found that remark interesting. As it turns out, I have one of the N900s with the "dark keyboard syndrome".

Since we plan to keep the illumination system of Neo900 similar to N900, I had a look at what may cause this. First, with the keyboard fully assembled:
https://neo900.org/stuff/werner/klig...bad-closed.jpg

For comparison, a healthy N900 looks like this:
https://neo900.org/stuff/werner/klig...ood-closed.jpg

I then removed keyboard frame and key mat, to reveal this unhappy sight:
https://neo900.org/stuff/werner/klig...d-open-top.jpg

Comparison with the good one:
https://neo900.org/stuff/werner/klig...d-open-top.jpg
https://neo900.org/stuff/werner/klig...h-open-top.jpg

Seen from an angle:
https://neo900.org/stuff/werner/klig...open-angle.jpg
https://neo900.org/stuff/werner/klig...open-angle.jpg
https://neo900.org/stuff/werner/klig...open-angle.jpg

Note that the light the LEDs leak onto the light spreader of the "bad" device seems brighter on the photo than it looks to the naked eye.

I tried to see if anything had come loose, but I couldn't feel any movement when applying pressure around the LEDs, and the light distribution didn't change.

So far, so bad. Other than diagnosing that this light spreader doesn't, I couldn't find much else. The cause for the sorry state of the light spreader is also unclear. Some possibilities:
- degradation of the plastic of the light spreader,
- undesirable chemical reaction between light spreader and adjacent adhesive,
- unusual environmental effects (maybe the light spreader just doesn't like the climate in Buenos Aires),
- some history of abuse (I got that N900 second hand and don't know what may have been done to it in the past),
etc.

Or maybe it was argentobacter plastivorus rex Of course, then it may have infected Joerg's phone while at the camp, then his entire stash at home, ... I guess nobody expected the zombie apocalypse to start quite that way.

Differences in "normal" degradation could also come from Nokia changing the chemistry between production runs. Of course, we wouldn't be able to tell. It could also be the result of a repair using a non-original light spreader, but I'd consider this unlikely.

Any ideas ? The problem seems to be rare in general, but if there's some precaution we could take to make Neo900 less likely to suffer such a fate, we'd of course like to do that.

- Werner

I have one n900 with "dark keyboard syndrome" and this syndrome is present since the first day of purchase in 2011

I bought mine N900 in November/December 2009 and also have the "dark keyboard syndrome" actually I never noticed it untill today :O I have second N900 "just in case" bought in 2012, taken out of box few times only to check if it's still working, otherwise resting in a box sealed in additional plastic bag - however I strongly believe it was not new but refurbished - and suprisingly it indeed has brighter keyboard (or maybe it's placebo effect as the contrast is not as big as in wpwrak's pictures, however the illumination seems more consitent across all keys and more white'ish).

This is the second time I WTF about the hardware I carry in my pocket every day - first one was also connected with Neo900 developement I think (or at least with joerg_rw), it was the fact that N900 had small internal battery to keep the date/time settings when taking out the main battery.

Brodyga, misiak: that may actually be good news. I didn't think that Nokia would have let devices with such a flaw out of their factory, but if it's a design or process flaw that exists already during production, we can test for it - and hopefully avoid following Nokia's example.

Much easier than catching something that may develop in the field, possibly years after production :-)

Thanks,
- Werner

Just to be 100% clear - I don't know if it was there right from the start or gradually developed over time... Like I wrote - I never noticed that something might be wrong with it. On my 2009 N900 the light is brightest on backspace key and 3 surrounding keys in top right corner. The top left corner is also brighter, but there is not as much difference. The darkest keys are the three columns in the center (starting with "T", "Y" and "U" respectively), and also the whole bottom row is noticeably darker then top one. It's like in the picture you posted ( https://neo900.org/stuff/werner/klig...bad-closed.jpg ).

I am sure this is the genuine device made by Nokia, hw rev 2101, disassembled once for cleaning, otherwise never repaired or anything, all parts are original. As I stated in my last post I'm almost sure that the other N900 (with brither and more white'ish keyboard) is a refurbished unit despite seller saying it's brand new (even the box contents were suspicious for me). Are you sure that the "unaffected" one you pictured is a genuine device manufactured by Nokia with original keyboard leds? Did you compare hardware revisions? I don't remember the rev of the white'ish led one, but can check later if that might matter.

it's highly unlikely somebody fixed a broken spreader during refurbishing. And the LEDs are same brightness on both devices, which can be seen clearly from the photos. Also refer to
http://neo900.org/stuff/joerg/random...t/DSCF0934.JPG
http://neo900.org/stuff/joerg/random...t/DSCF0935.JPG
http://neo900.org/stuff/joerg/random...t/DSCF0937.JPG
for a considered 'OK' reference sample

misiak, "bad" and another "good" one (The one in the pictures is currently disassembled. Let's call the other good one "good2".) both say they are hw version 2101. But that may not tell us much.

The code imprinted on the light spreader is 059705 V5 934 for "bad", 059705 V5 946 for "good", and 059705 V5 951 for the "good2". No idea if that code means anything, though. Joerg suggested that "934" may be the production date, e.g., 2009, week 34.

Both my "good" devices are former Mozilla units, so I'd expect them to be as genuine as it gets.

- Werner

Just for information, as I am previously said I bought mine N900 (HW Rev. 2204) in 2011 new from Nokia official store in Armenia and the keyboard light problem is present from first day of purchase.

My light spreader and backlight is *exactly* like shown, but only since baking the board in a reflow oven, to resolder the modem chip that had cracked away (the "no SIM" / "unable to initialise modem" fault). So seemingly, intense heat due to repair work can cause the discolouration, or maybe less heat over a longer period of time?

https://neo900.org/stuff/werner/klig...h-open-top.jpg

As for "prevention", it would be nice if the thing was removable. As well as the camera module, which I also destroyed in the process.

moved lightspreader stuff to THIS new thread here