Why doesn't my keyboard repeat a letter I press?

Sounds like your keyboard is malfunctioning.

On my PC there is a setting called Character repeat where you can set Repeat delay, and Repeat rate.
Settings> Control panel > Keyboard> Speed > Repeat delay
I assume the Mac has a similar procedure.

Yes, when I go onto System Preferences on the “Keyboard” section there is an option called Key Repeat which I can select between off, slow and fast.

I selected fast and “short delay” but still nothing happens.

It looks like this might be an operating system thing… do you have Lion?

It depends on the app. In some apps the keys repeat and in other apps it give you a accent pop-up like this. It your want to turn this off so it always repeats you can enter this in the Terminal. Open Applications-> Utilities-> Terminal and enter:

defaults write -g ApplePressAndHoldEnabled -bool false and then hit enter. You might have to restart all your apps for it them to see the change.

@dappled_leaves Yes, I have the latest version of Lion.

@johnpowell Thanks! Now it seems to work as I wanted. Is there anything I should write in the Terminal if someday I wanted this to return to normal (i.e. undo this action) ?

Sure, just change false to true.

defaults write -g ApplePressAndHoldEnabled -bool true

@johnpowell Much appreciated.

“Sure, just change false to true”
That is funny if taken out of context!

Both Windoze and Linux have options to alter the keypress delay and repeat timings. I can’t say for OS X, but it sounds like something similar has been set or turned off on your system.

Hey @johnpowell, does this interfer with the keyboard illumination?

Since I did this, the lights won’t turn on.

Thanks.