USB keyboard usually works but randomly doesn't

[Arellcat]

My late-2008 Mac Mini with OS 10.6.8¹ is behaving very oddly with my current keyboard—or should I say, my keyboard is behaving very oddly with my Mac.

For years I used my Apple Extended II via a Griffin iMate without any problems. OK, so the iMate made the Mac think the KB was not just ten-keyless but arrow-keyless/home-keyless as well.  I still would be using it if it hadn't developed chatter on one key.

I now use a (second hand) Das Keyboard Professional Model S, which l like very much.  It's does 5-key rollover which is enough for me.  But on waking from sleep, sometimes my Mac seems sluggish in reading the keyboard's signals, meaning that if I type quickly, a good third of all the characters are missing from my words.  Often it's the same characters because of the polling order the Das uses in reading each key.  And sometimes, on waking from sleep, the Mac completely fails to read the keyboard at all—even though the Mac can see it attached as a device.

I did trial a Razer² keyboard for a few days, a good while before I bought the Das, and I don't recall the Mac behaving strangely at that time.  The Das also has a 2-port hub built in, so has two plugs on the cord (one for the KB, one for the hub).  It doesn't seem to make any difference to which USB sockets on the Mac I connect the Das, or whether I leave the 2-port hub plug dangling in fresh air or not.

I've tried adding a short extension cable to the Das's main cable, or adding the extension to one of the sockets on the 2-port hub.  I've tried running the keyboard directly from the Mac on either its slow or fast USB ports, and nothing has made any difference in performance.  The only solution thus far is to unplug the keyboard and plug it back in again while the Mac is running.  It works every time, but it's getting annoying.  I'm actually starting to wonder if my Mac is behaving normally, and the Das's firmware is on the fritz.  If I plug the iMate and Extended II back in, no problems³ with USB.  From a poke or two around on the internet, it seems it might well be a problem specific to the USB firmware of the keyboard, which is a bummer.

The current setup is:

Onboard USB:

• Mouse

Onboard high speed USB:

• Das Keyboard 2-port hub:
• Occasional USB stick, usually absent
• USB3.0 external drive for Time Machine
• 4-port USB-powered mini hub:
• Das Keyboard
• Headset for audio
• Webcam
• Extension cable for occasional cameras, GPS, etc.

1 I'm a dinosaur.
2 The Razer's key switches were great, and personally preferable to Cherry MX Blue, but the ergonomics were peculiar, as was the keyboard's typeface.
3 Aside from the Mac occasionally waking itself from sleep up at random times of the day or night, with the system log citing USB7 as the reason, which it's done ever since I bought the thing.

[Jaded]

Try:

Downloading and running the 10.6.8 Combo update from the Apple website. https://support.apple.com/kb/DL1399?viewlocale=en_GB&locale=en_GB This puts all the 10.6 updates onto the machine at one time, resolving any problems there might have been from one update after another.

Reset the PRAM - restart the machine and hold down CMD ALT and P and R at the same time. Wait until the third restart "bong" before resleasing the keys.

Restart the machine, holding down the  CMD and S keys until a load of text appears on the screen. When the text finished scrolling, there are two lines of text at the bottom the upper one has 'fsck' in it and the lower one 'mount'

Type in (exactly) the first line and click Return. When it has finished, check the messages on screen. If it says the file system was modified, do it again.
Then type in the mount line and press Return.
When it has finished, type exit and Return

After that, there are more, deeper things to try...

[David Martin]

Next stage is the chicken sacrifice and the correct incantations to Cthulu..

[ian]

Finestre is the Demon of Such Things, and thusly rightfully the recipient of any sacrifices you may care to make. Cthulhu is her pet, erm, thing.

They say wifi is the devil's radio, but she practiced with wires first and called it USB. That was before she moved on to Bluetooth. Everything was practice.

Follow Jaded suggestions, they're the usual starting point, but if other devices work and USB is generally fine, then that points the finger at the keyboard. You may want to try the manufacturer's support and see if they have suggestions.

It might be worth upgrading 10.6.8, my early 2009 Mac Mini runs El Capitan without a hitch. Many driverless devices do require later versions (I couldn't see a version specified on the Das website) to function correctly.

[Arellcat]

In the interests of closure, or at least an update, I ditched my Das keyboard and went back to the Razer Blackwidow Tournament Edition that I'd ditched in favour of its successor.  The Razer key switches are weighted slightly heavier than MX Blues, which suits me nicely.  And although I'm used to it now, for a good while the Razer keycap typeface really gave me the boak.

However, to return to the subject at hand, footering about with the PRAM and file system checks merely showed my computer was ticking along quite happily already.  The Razer performs fautlessly over USB using the same port that previously received the Das keyboard.