Repair of the Week: A Bizarre Keyboard Problem

A MacBook Pro came in last week because it refused to render the “d” character when its key was pressed. This is bizarre behavior that I hadn’t seen before; usually when a customer reports this sort of problem, technicians don’t immediately believe it.

We confirmed it was an issue and tried an external keyboard first. The problem persisted, so we knew it wasn’t the keyboard or top case. In MacBook Pros with silver keys on the keyboard, the keyboard and top case are two separate parts. Confirming it wasn’t either, we booted the computer up from a known-good external source. Your system’s restore disks are the perfect choice here, but we use a fancy NetBoot system that’s much faster and versatile.

The problem went away when booted from the external source, confirming that hardware was not to blame. So, after a restart we started narrowing things down. By creating a new account on the computer, you can determine whether the problem is system-wide, or isolated to one particular user. Mac OS X is designed for multiple users, but there are core components that all accounts use.

The new account did not show the symptom. Lower case “d” worked just fine. This means we needed to look at the user account.

Knowing from experience that this sort of thing usually is a result of fiddling with the Universal Access preference pane, I headed there to look for the case. No luck. Google searches yielded little, and the replacing of various kernel extensions proved ineffective. By chance, I’d clicked on Macintosh HD once, and the name became editable. I decided to try the “d” key again, and the computer spoke “Macintosh HD.”

Off to the Speech preference pane, where I unchecked “Speak selected text when the key is pressed” from the Text to Speech tab. Somehow, lower-case “d” was set to make the computer speak selected text.