Hi,

While back I got an Cherry RS 6000 AT keyboard. It was filthy so before I went to test I've done an total teardown and cleaned it (excluding the internal flex with traces and whatnot). I've let it dry in the sun for a few hours then I took everything home and put it to dry in the garage for a day. Then I reassembled it and tested it.
NUM, CAPS and SCROLL LEDs flash normally and I get no keyboard error after POST, indicating the VCC, CLK and DATA pins are getting from the board to the controller.
Sadly, there's no response to any keypresses.
What I've tried so far:
Scuff the pins on the flex and PCB lightly with 400grit sandpaper
Go over pads with an lead pencil (made sure to not short pads by accident)

But to no avail. When I touch the PCB in some places with my fingers I can get the LEDs on it to flash briefly, but that's about it. I had double checked if the cables were okay (they are) and this is where my knowledge ends. Looking at the flat flex (or whatever it's called) there is some corrosion (mostly black oxidization) on the silver traces, but not enough that the whole keyboard would just not work. No visibly torn traces tho...

Any ideas?