One row of keys on the iMac keyboard has suddenly gone dead.

The keys that no longer work are on the lower row, from Z through the / (plus the left-most Command key and the space bar on the bottom row). System is iMac (spring 2009), running 10.5.8, with a wired keyboard (the one with a number pad).

Solutions tried:

• change to another keyboard - this second keyboard showed exactly the same symptoms.
• switch keyboard(s) to another USB port
• reset SMC (twice)
• reset PRAM (twice)
• switch to another User Account
• boot from Install disc
• clean contacts on USB cables (and sockets)

None of these things worked. The same keys are dead, now on both keyboards.

But what is really bizarre is that when I took the two keyboards and tried them on a second computer (my MacBook running 10.7.2). It then showed the same symptoms - same keys dead.

So to rundown:

• keyboard A initially stopped working on machine A
• keyboard B was plugged into machine A as a test, but also didn't work (in exactly the same way)
• machine A was restarted, PRAMMed, etc. as described above, but neither keyboard A or B will work on it, even when the machine is booted from an install disc
  
• machine B (the laptop) works normally, with its own keyboard
• plug in keyboard A - no go. Same symptoms - same keys don't work, everything else fine.
• plug in keyboard B - no go. Same symptoms - same keys don't work. The first keyboard has Zombified the second one, or killed machine B in exactly the same way!
• unplug keyboards, restart machine B - it returns to normal.

What is going on? Any suggestions would be much appreciated ...

The wired keyboards - how old are they? The reason for asking is that there are actually two different model Apple Aluminum wired keyboards. The older model will work with OS X Leopard through Mountain Lion. The newer model will only work with OS X Snow Leopard 10.6.8 through Mountain Lion.

It is strange though since your MBP is running Mountain Lion, both model keyboards should have worked. Unless you just happen to have two defective keyboards?

Keyboard A in the story is the one that came with the iMac in the spring of 2009 - a thin aluminum type. Keyboard B is a completely different type - the kind with the curved acrylic base plate with large black keys (I think it was a replacement for the one that originally came with my G4 ...)

When I first tried Keyboard B, and got the same 'dead zone' result, I of course assumed that this pointed to the iMac itself as the culprit. But finding that both keyboards have exactly the same dead zone when plugged into the MacBook throws that theory out the window.

It's as though Keyboard A has died, but has become a Zombie, contaminating Keyboard B in exactly the same way. I thought that perhaps there might be some 'gunk' or something on the USB plug, that might have transferred from A to B, and then to the MacBook, so cleaned all plugs thoroughly with alcohol, but nothing has changed.

davebull said:

But what is really bizarre is that when I took the two keyboards and tried them on a second computer (my MacBook running 10.7.2). It then showed the same symptoms - same keys dead.

Click to expand...

Good idea checking both keyboards on a 2nd computer. This sort of thing is pretty rare. Unless there is some sort of software issue on both computers (since both computers are yours & possibly setup similarly)...as chscag mentioned...both keyboards could have gone bad in some unusual way.

The only way to test further is...try both keyboards on a 3rd computer (not owned or setup by you):

- If the keyboards do not work...then they are most likely "bad".
- If they do work on this 3rd computer...then you may have installed some sort of software that must be conflicting with the operation of the keyboards.

- Nick

Update: I decided to take a chance and use the keyboard from Machine C, a third computer here (an old G4). Keyboard C is the curved acrylic type.

I first tested it on Machine B, the MacBook, and it behaved OK. I then plugged it into Machine A, the iMac, and ... OK.

I then re-tested Keyboards A and B on the iMac, but no, they both still have exactly the same pattern of dead keys as described above.

So my main problem (seems) solved - the iMac is OK - but the remaining mystery is how Keyboard A was able to contaminate Keyboard B with exactly the same pattern of dead keys.

Anyway, thanks for the suggestions you made ...

Congrats on at least getting something to work (3rd keyboard).

I just noticed that your location is Tokyo.

Just so we know...are you:

- Using English or Japanese keyboards?
- What language is the Mac OS running in (English or Japanese)?

Just asking...in case there's some sort of language/keyboard conflict.

- Nick

All my hardware is locally purchased, so it all comes with the keyboards designed for the Japanese market. I run the OS itself in English, but a few of the applications in Japanese. (This wonderful feature is possible these days because you can change your International selection, start a program - which will start up with the selected localization, then change the International selection back again ...)

And of course I change the language input back and forth hundreds of times a day as required (sometimes in the middle of a sentence). I've never had trouble with language aspects over all the years using these OSX systems.

This problem really doesn't seem related to that sort of thing. On the face of it, it now seems to be simply a case of an ageing keyboard which developed a hardware fault. The hugely confusing aspect is that the replacement keyboard I initially tried had (and still has) exactly the same pattern of dead keys, leading me to suspect the iMac itself. Such a coincidence just doesn't seem possible.