I hate these HP slide switches! What you have to do is remove the front panel from the unit and then separate the board from the metal
front panel. You will then see all the switches and the mechanisms. Now you have to slide each switch all the way out one end. Be VERY
careful when you do this, because if I recall, they tend to hang up on solder bumps if you slide them out the wrong direction. Carefully note
the position and orientation of each switch before you slide them out so you can reverse the process upon reassembly.
With luck, all that you will find is the switch covered in dirt and grease - a simple alcohol wash of the switch fingers and the underlying gold
trace that the fingers slide on will cure your problems.
Worst case is that one (or more) of the switch fingers is broken or gone. The only way I've been able to fix that is by scavenging from another
switch. You can heat stake a tiny piece of metal to simulate the finger if you can find a suitable piece of metal. Of course, if the underlying
gold trace is severely scored, then you are completely out of luck as no contact will ever be made.
There's nothing really complicated to the mechanism and it will all be clear upon disassembly.