Having problems using KVM/external monitor

Factual Questions
1

For a long time now, I’ve used a KVM switch in order to have my office PC and my personal MacBook accessible through the same keyboard and monitor (I never got the mouse to work properly through the switch, so I just use a wireless mouse for the laptop.)

Last week, my hard drive failed and I got it replaced, restoring my data from external storage. However, all of a sudden, I cant’ get the KVM switch to work right, or maybe I can’t get the MacBook display to work right.

It used to be when I plugged in the video (in the video input) and keyboard/mouse cord (USB), the laptop desktop would immediately pop up on the monitor (or, rather, the sign in window would). I could leave my laptop open and use it both ways, through the KVM keyboard and monitor and through the trackpad/built-in display. Or I could close the laptop and use it in clamshell mode.

Now, when I plug in the video and keyboard from the KVM, the built-in display goes blank and the KVM display acts as if there’s nothing built in. When I unplug the cords, the regular laptop display comes back.

What should I check here? This is the kind of problem that’s difficult to take to the Genius Bar, because I can’t cart my office computer with me.

2

Try two things:

  1. The “export video” function might not be on on your laptop. I’m not familiar with Mac keyboards, but on most laptops, its a function key plus the LCD screen button. This function is what lets your computer know you want the screen output to go to the KVM.

  2. Put the switch to the KVM, then restart your system. Your computer may need to detect that the devices are there, and sometimes the only way it does it is if they are present on startup.

Good luck!

3

I figured it out with the help of the Genius Bar. For some reason, the reinstall resulted in a switch off of “mirroring,” so that explained the blank desktop – all the actionable items were on the other desktop, which was not showing up because I had worn out my Mini-DVI/VGA adapter cord.

I had done the “mirroring” thing back when I first set this up, but that was years ago, so I had forgotten about it. It annoys me how sometimes these little things can be so hard to find.