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Old 07-29-2011, 08:32 PM   #3 (permalink)
stevew
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Default Re: Fixed my "double type" keyboard!

Ira - I had changed the keyboard some months ago, with no apparent success. At the time, looking at the ribbon, I then clearly understood why the issue seemed like it had manifested itself there. Each button on the keyboard presses down on a corresponding metallic (bubble style) button on the ribbon, which in turn, shorts out the corresponding pad on the PCB. The bubble style metallic buttons on the ribbon have a specific spec they are built to, in order to maintain the tactile feel on the keyboard and produce the desired result when keys are pressed. If the spec isn't within proper tolerances, the failure would result in either too much or too little contact on the PCB. Kind of like a debounce buffer in a touchscreen keyboard, but mechanical. If you examine the ribbon, you'll understand exactly why the failure results in that stupid double type issue. Now 2-3 days and working flawlessly, so it really was the ribbon - and only that. Those who say it's software related haven't a clue of what they're talking about.

It could never be a keyboard issue and as far as the PCB, it's simply a flat board with brass pads and it would be impossible to reproduce that result -- the whole feel of the keyboard is generated by the ribbon.

It's also noteworthy that the ribbon is the weak link in the chain and would be prone to failure at some point in the device's life.
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Last edited by stevew : 07-29-2011 at 08:36 PM.
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