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"Maybe It's a Piece of Dust" (theoutline.com)
An anonymous reader shares a report: I was in the Grand Central Station Apple Store for a third time in a year, watching a progress bar slowly creep across my computer's black screen as my Genius multi-tasked helping another customer with her iPad. My computer was getting its third diagnostic test in 45 minutes. The problem was not that its logic board was failing, that its battery was dying, or that its camera didn't respond. There were no mysteriously faulty innerworkings. It was the spacebar. It was broken. And not even physically broken -- it still moved and acted normally. But every time I pressed it once, it spaced twice. "Maybe it's a piece of dust," the Genius had offered. The previous times I'd been to the Apple Store for the same computer with the same problem -- a misbehaving keyboard -- Geniuses had said to me these exact same nonchalant words, and I had been stunned into silence, the first time because it seemed so improbable to blame such a core problem on such a small thing, and the second time because I couldn't believe the first time I was hearing this line that it was not a fluke. But this time, the third time, I was ready. "Hold on," I said. "If a single piece of dust lays the whole computer out, don't you think that's kind of a problem?"
Sometime around 2005, I bought my first Thinkpad - second hand because they were pretty expensive machines - from a guy who had bought it overseas. I used it everyday as my work/home machine for about three years including travelling all over the world and taking it out on various work sites.
One day, the left shift key on the worn-smooth keyboard fell off. The clip had worked its way lose and the key no longer had a proper detent. I thought I had had a pretty good run with the thing, but figured I'd see what a spare part would cost. To my amazement, the machine was still under IBM's global warranty. I rang them up on the toll free number, gave them the serial number, and asked if the keyboard was still covered. They said the parts were, but not labour, and asked if I would be able to change the keyboard myself. About 3 days later a new keyboard was couriered to me. I screwed it into place and got another year of use out of it before it just became too slow.
I guess you payed for it in the price back then, but that is how you do customer service.
"Key bounce error".
When you depress a key, any key, the contacts do not perfectly connect; they bounce. Electrical engineers fight key bounce error — basically by trial and error — with debounce by adjusting the computer to read the key input then wait. If there are other bounces within a few milliseconds, they are ignored. Then the computer starts looking for keyboard inputs, again.
When keys go bad— one way that keys go bad is the contacts don't contact-and-release as quickly as expected, and, the computer reads a second key input.
That's why, on some keyboards, the "space bar" goes bad, or the 'E' or the "T" or "A" or "O" or "N"...
"Bouncing is the tendency of any two metal contacts in an electronic device to generate multiple signals as the contacts close or open; debouncing is any kind of hardware device or software that ensures that only a single signal will be acted upon for a single opening or closing of a contact."