I picked up a Ducky One Mini at a flea market yesterday, and after cleaning it extensively it seems to be working pretty well for the most part. I'm using it for writing and coding, so not having dedicated arrow keys will take some getting used to, but other than that it seems neat enough for the price I paid.
However, the alternative graphic button (on the right side of the space bar) is completely unresponsive. Pressing it just makes no difference at all. I used a tool that maps keyboard presses in Linux (xev), and it showed nothing when Alt Gr was pressed (just like the Fn button), so it seems no signal is being sent from the keyboard to the computer.
It could be that this is due to some setting made by the previous owner, or maybe there's something else going on. Maybe I need to update the firmware. Maybe it's broken. I have no idea.
The back-light behind some of the numerical keys is also disabled or broken, but it doesn't bother me much as I'm not a big fan of back-light anyway.
But if anyone has any suggestions what to try for the alternative graphic key it would be much appreciated! For now I have re-routed right super (Windows button) to be read as Alt Gr, but it's not very convenient when writing Latex and using a lot of curly brackets. :)
It is possible that the previous owner flashed firmware that doesn't bind that key to anything. So the first thing to try would be flashing firmware that does bind the key. If that doesn't work, the switch might be the problem. You could check on the back of the pcb if the soldering looks any different from the other keys. Even if it doesn't you could reflow the key. If that doesn't work you can unsolder the key and pull it out, open it up to see if anything is messed up like the contact leaf. You could try a different switch in that spot. If you put in a fresh key that works in the old spot and it still doesn't work it might be the pcb. Maybe you need to reflow or replace the diode. If that doesn't work it might be the contact pads on the pcb for the switch or the diode. When unsoldered and with the solder removed you should see a metallic ring around where the switch pin goes. If that is (partially) missing it will be trouble. It could also be the 'wire' that is etched into the pcb that goes from the pad to the controller. Either fixing the pad or jumping the wire is a bit more advanced (and a pain in the ass). I don't have experience with that. Hopefully the problem is earlier in the chain. Good luck!
Before opening up or resoldering any switches, I'd short the two pins with something (tweasers or similar) to confirm or rule out the switch itself as the cause.
Thank you so much for the thorough response!
It seems it's easier to deal with the firmware from a Windows machine, so I'll deal with that back in the office next week.
If that doesn't help I'll take it out of the case again and see what's up. I don't have a soldering iron yet, but if it's an obvious problem this might be what pushes me over the edge. :)