Any ideas on how to diagnose a 'dead keys' problem on an iMac (Intel)?
July 23, 2013 9:37 PM   Subscribe

One row of keys on the keyboard has suddenly gone dead, and none of the obvious fixes (switch keyboards, etc.) seem to work.

The system was fine last night, and I sent it to sleep as usual. When I woke it up this morning, the keys were dead. I made no changes to the system at all recently (new installs, font changes, etc.).

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 (Intel), about five years old, running 10.5.8 (happily), with a wired keyboard (the one with a number pad).

Solutions tried (all to no avail):
- change to another keyboard
- switch keyboard(s) to another USB port
- reset SMC (twice)
- reset PRAM (twice)
- switch to another User Account

Something that might (?) be a factor is that we had a giant electrical storm a couple of weeks back. Before I could shut all our computers down our neighbourhood took a lightning hit, and the main breaker in our building flipped. I was afraid that we might have lost some of our machines, but when I brought everything back on line, one at a time, everything was OK, and there have been no irregularities since then (computer in heavy daily use).

I'm kind of running out of ideas ... Anybody have any suggestions?
posted by woodblock100 to Computers & Internet (12 answers total)
Do an Archive and Install reinstall of OS X 10.5. Patch it back up to 10.5.8. Read the linked doc to understand where your old System folder will go.

If a system reinstall doesn't work, then you almost certainly have a hardware issue on hand that will require a logic board swap at Ye Olde Apple Store.
posted by Blazecock Pileon at 9:43 PM on July 23, 2013

Can you VNC into it? If that works, I'd think it's a hardware problem (though after your steps 1 and 2, that seems well weird to me). If not: software. Fiddle with your keyboard settings. Somehow.
posted by pompomtom at 9:44 PM on July 23, 2013

Try the Keyboard Viewer. This is in the language setting preferences pane and should show you what your current keyboard inputs are set to. I can't say for sure that this would catch it if there's a problem with that end, but it certainly could help narrow it down if, say, you hit some shortcut that put you into a different keyboard mode.
posted by Lady Li at 9:47 PM on July 23, 2013 [1 favorite]

If you switched to a freshly-made user account, that probably rules out a preference-related issue such as keyboard localization. If you switched to an existing user account, then keyboard preferences could be a problem. Be sure you are switching to a fresh user account.
posted by Blazecock Pileon at 9:51 PM on July 23, 2013

If you boot a livecd/usb you should be able to figure out for sure whether it's a hardware problem or not.
posted by 23 at 10:32 PM on July 23, 2013 [2 favorites]

This sounds like a hardware problem with the iMac itself.

To check, try booting from the installation DVD (whatever one you have). If the keys don’t work when running from the DVD, then the problem is hardware, and you’ll have to take the computer in for service.

If you don’t have an installation DVD, then I would take the computer in anyway. The people at the Apple Store (or wherever) should be able to check.
posted by Renegade Duck at 10:33 PM on July 23, 2013

Response by poster: Keyboard viewer is how I got this message typed. I forgot to mention above that I have also checked all the various Universal Access settings, to see if something was 'on' by mistake.

The user account was freshly created for this diagnosing.

As for VNC, no idea. I can't get Chicken to login properly; it just crashes on each attempt. Might be because the host password contains a letter from the 'dead' row ...?

Archive and Install is certainly not something I want to wrestle with - not with five years of updates and customizations in there, but I think that's not necessary. I just booted up from the install disc to check, and ... the keyboard is still borked.

If this were the old days, I would check the chips, to see if they were all seated properly, but I can't see how that would possibly cause such a problem on a modern machine like this (and certainly not just for one row of a keyboard ...)

Looks like a job for the service center ... :-(
posted by woodblock100 at 10:53 PM on July 23, 2013

I got a new iMac seven months ago. I made myself absofuckinglutely insane over the last couple of weeks trying to get to the bottom of intermittent keyboard failure of certain keys in weird patterns.

And then it got worse and I got fed up and took myself to the Apple Store with just my keyboard in tow. (BTW I haven't bought AppleCare yet.)

They took a good close look at the keyboard externally and (rightfully) acknowledged that I obviously hadn't poured a cup of coffee into it. And so diagnosed it as "looks like your keyboard is fucked up, sorry, that must have been frustrating."

And they sent me home with a new keyboard.

That is all.
posted by desuetude at 11:38 PM on July 23, 2013

- change to another keyboard

Can you elaborate on this? Was it wired or wireless? Have you tried a non-apple USB keyboard?

Do you have windows installed in boot camp, and have you tried that out with the other keyboard?

Have you tried the original keyboard on a different machine?

I'm struggling to see a way that one row could be bad on multiple keyboards on any USB port that wasn't some software problem. USB either works, intermittently works like crap in non-predictable(at least in this sense) ways, or doesn't. Nonetheless, I'd try all that stuff.

as for the storm, buy one of these in the 360va variety for the iMac. They're cheaper than UPSes, have no batteries to die, and just generally hardier as they're true isolation transformers. After losing a couple motherboards to electric dumbness I'm not playing around with that ever again.
posted by emptythought at 12:39 PM on July 24, 2013

Response by poster: All keyboards tested (now three of them) are wired Mac models of various types.

I have no Windows here to test, either real or virtual.

original keyboard on a different machine ...

It's a Zombie! It has killed the second test keyboard!

To rundown:
- keyboard A stopped working on machine A
- keyboard B was plugged into machine A as a test, also didn't work (in exactly the same way)
- machine A was restarted, PRAMMed, etc. as described above, and neither keyboard A or B will work on it, even when the machine is booted from an install disc

That was yesterday. Now today, at emptythought's suggestion, I test using another machine:
- machine B works normally, with its own keyboard (this is a laptop)
- plug in keyboard A
- no dice. Same symptoms - same keys don't work, everything else fine.
- plug in keyboard B
- WTF! Same symptoms - same keys don't work. The first keyboard has Zombified the second one, or killed the machine in exactly the same way!
- unplug keyboards, restart laptop, which seems to be normal (I'm typing on it now).

I have a machine C here, but there is no way I am going to plug in either of these two Zombie keyboards, or use its keyboard back on machine A. I can't take the risk!

Talk about a head-scratcher!
posted by woodblock100 at 2:46 PM on July 24, 2013

Response by poster: Zombification ... contamination ... this leads to another idea.

What if perhaps there is some gunk on the USB connector, causing one of the pins not to be passing current properly? Plugging in a second keyboard picked up some of the gunk ... Putting them into the other machine transferred it there too. Could the loss of one pin cause this sort of dead zone on the keyboard?

Anyway, back in a few minutes; I'm going to get some alcohol and tissue and try to clean all these connectors ...
posted by woodblock100 at 2:58 PM on July 24, 2013

Response by poster: Well, it was a good idea. But no change.

To recap:
- machine A (the iMac) will not work with either keyboard A or B
- neither keyboard A or B will work with machine B (the laptop)
- machine B works fine with its own internal keyboard

Machine C (a G4) is working fine with its own keyboard, but I'm not going to try any more combinations; I don't want to take that one down too ...
posted by woodblock100 at 3:20 PM on July 24, 2013

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