The wizard with the wireless keyboard is INSIDE the circle
All the other tech is outside.
That'll still fry the keyboard. Pretty quickly as well, since the building magical energies can't escape the circle.
I think simpler solution would be one of two ways. Either you go ancient tech or you build a magic to technology adapter.
The first is pretty simple. Build a keyboard like an old mechanical typewriter and have them work through pulleys and wires to be a long distance away, before it gets in contact with the electronics. The image can be projected through lenses and mirrors, so the only thing that arrives at the wizard is the image itself, without anything electronic.
The magic to technology adapter works similar, though it replaces the pulleys and wires with magic. There are multiple ways to do this. For example, you can create a magical keyboard that projects an image of the pressed keys and a camera sends it to the computer.
Another way to go would be completely magical, but I guess it's going to be a full time job just maintaining it. The main benefit to having a computer would probably be the internet. You can't really emulate a regular computer, but you can emulate an internet machine. There are some basic protocols, and you'll have to build a magical construct that is able to interpret the information through the right protocol. After that, you'll need a connection to the internet. Again, the most robust way to do so seems to be using light to transmit the information. Get an optic cable, create a magical construct to communicate with the internet in the right way, and you are golden.
Then again, it's probably easier to bribe a spirit of intellect to hook up to a cable and do all that for you.