Ok, here is the final fix! I already made it on my device while waiting for some replies, and it worked good! ;)
The problem is the copper push plate underneath the trackball that is placed directly onto the motherboard of the device.
The problem is that underneath this plate there must be some corrosion or some kind of dust or some glue slipped due to the heat of the device (you'll understand why the presence of glue by reading ahead in the post).
In my device there was some glue and some corrosion!
The part we are talking about is a little black plastic square with a round metal plate in the centre.
This square is placed at the centre of the 4 leds and 4 trackball sensors.
The round plate we need to clean is placed up on the plastic base and is keeped still with a light brown square tape that is glued on to of all (there goes the glue!).
Here is what you need to do:
- turn off the device and remove the battery, the sim card and the memory card (if used).
- disassemble the 8100 so to reach the motherboard easly (8100 Disassembly photos and instructions).
- from just one corner of the base and with a sharp knife CAREFULLY pry the tape up so to reach the plate and pry up that too -- as you could see the plate is only touching the black square base and is keeped still by been glued at the tape on top of the base.
- remove the plate from the tape WITHOUT removing complitely the tape from the square plastic base -- just slip the plate away from underneath the tape.
- now act on the plate with a small metal object and scrap off everything you have underneath it -- you must act unlit you see the plate as clear as possible -- it does not matter if you scratch the metal of the plate because it will work anyway -- JUST DON'T BEND IT!!!
- when finished, just clean the base contacts with a really clean piece of paper and finally blow air on it with your mouth just to remove the dust -- there sould be no dust between the plate and the base!!
- replace the plate underneath the tape and up on the black square base in the same position as it was before -- just centre the base!!!
- replace down the light brown tape and check if it glues back on the base corner from wich you lift it up -- instead NOT just use a little piece of black tape on the corner and on any other corner that does not glue any more.
That's it!! now it should work. It took me about 15 minutes to do everything (same time as writing this post!)
Hope this could help.
Thank you all.