I have a couple of LK401 keyboards and they generate a 'keyboard error - 4' error on power up test when attached to a VT420. The problem seems to be one or more keys that are 'stuck on'. When the keyboard is turned upside down and shaken I can get the self test to pass. Is it possible to open the keyboards and repair this type of problem? I also have LK411 keyboards that have a PS/2 type of connector, is there an adapter to let me use these keyboards instead of the LK401s? Are the signals the same, only the connectors being different? Doug