Thought Experiment: You solder a very tiny connector to an breakoutboard to try beep out the thing you connected to that connector. You find a few connections but for Farad sake you can not find others.

You totally must have broken some connections on the disassemly of that board, so you buy a few more components. Would you also check your Connector on that breakout board if that has all the connections you think, beep out all 28 Pins?

I did all this without checking the soldered connector. So i found all the missing connection for the Diodes where on PINs that where not really soldered on the Connector Breakout. I checked then with thin wire direct on the FlexPCB connector and there where all my missing connections.

I present you the Blackberry Q10 Keyboard Backlight Pinout :D

The resistor on this circuit seem to be in the ballpark of 1 Ohm. I tested the LEDs with 3V and they seem to like this voltage, 2.5 is minimum but also very dim

Things i learned: 

• Solder once Beepout Twice all your connections, every pin
• Soldering 0.4mm is Hard