Replaced the KVM switch for my retro rigs a few days ago, and ran into some problems getting the keyboard working. The "new" switch is an old Black Box Servswitch Jr. rev 1.2. Tried a few different keyboards now, and I can only get one of them working.

The only thing I've found so far that the non-working keyboards have in common, is that they're of the type that can be connected by either USB, or PS/2, using a "dumb" USB to PS/2 adapter. Would guess they detect the connection type and chooses protocol according to that. One of the keyboards, a Qpad MK-50, is different in that it's got a PS/2 connector, and uses a PS/2 to USB adapter instead of the other way around, but that shouldn't matter, electrically it''s probably all the same.

The only keyboard I got to work is an old low budget PS/2 one, it's got what looks like a QC sticker from '04. I highly doubt it can do other protocols than PS/2. Unfortunately I don't have any other "pure" PS/2 keyboards to try out.

Since PS/2 can't be hotplugged, it wouldn't surprise me if the KVM switch does some magic with the keyboard, I doubt it's a simple passthrough at least. My theory is that this problem has something to do with that, and the switch being from a time when those combo keyboards didn't exist.

So, any ideas at all of how to go about this, except getting a nicer PS/2 only keyboard or live with the crappy one I've got? Is it perhaps possible to wire/mod those combo keyboards to PS/2 only some way?