Dead key on 35s

[jebem]

(03-12-2016 02:46 PM)Tugdual Wrote:  Thanks all for answers.
@Thomas, nice picture set; so apparently the keyboard is hidden below a white layer with what seems to be bumps? Terrible technology!

Indeed, the pictures do not show the key domes on the PCB.
These domes are not that bad and are in line with other HP machines made in China from that era.

From your description, I believe that the problem lies in the plastic key itself: Each key has a small pin that can be bent or broken or smashed due to unknown reasons.

If you take the time to open your 35S (you need to break a number of plastic rivets in addition to undoing the tiny screws), you may check this issue for other keys as well.

If this is the case, the repair should not be that difficult. Basically you may just glue the bent pin using fast setting epoxy adhesive like Araldite.
If the pin is totally smashed, then you need to make a small pin from a similar plastic material. I would not use metal pins as these may cause damage to the domes in the PCA.

If not, have a look to the key domes and use a can of compressed air commonly found in electronic shops to clean any eventual residues.

Also it is important to check if there are signs of liquids that may have been dropped over the keyboard, specially sugar drinks.

The same epoxy adhesive can be used to fix the PCA against the plastic rivets.
Great care must be taken to ensure that the adhesive does not leak into the key domes underneath while doing this!
That is why fast setting adhesive (5 minutes) must be used.
When doing this, I put a small quantity of adhesive on a small group of rivets, let is set for 5 seconds, then turn the machine upside down for another 5 seconds and keep doing this for a couple of minutes until the adhesive stops moving. Then repeat the procedure for the next group of rivets until done.

It requires a lot of care and patience but it pays in the end.

As I see it, this is not that cheap calculator by any means. Prices goes around 60 Euros+s&h mark in several places including eBay.

For comparison, a cheap calculator would be a CASIO CLASSWIZ fx-991EX or their regional variants (for my region that would be a fx-991SPX Iberia) costing about 22 Euros around Europe.