Caps lock can be turned on and off for a few seconds after turning the mother board on but then it stops responding.
That means the mainboard isn't acknowleding the KB controller's send attempts - once the internal queue fills up the LED isn't changing any more.
Amigas boot up fine w/o a keyboard.
I'd swap the chips one for one into a working machine to see if they work. Usually one of the CIAs, Gary or the CPU are fried.
