No True Scotsman wrote:
It has two flat ribbon cables, one with 7 pins and one with 12 pins. I presume one is for rows and the other is for columns.
I have doubts about this assumption. To be on the safe side, I'd just view them as 19 unknown pins.
I'd use a variation on the procedure George suggested. Press and hold one (or several) keys down; then, go hunting until you find some continuity. I'd use a pattern like this:
- Focus on pin 1: Test from 1 to 2, then 1 to 3, 1 to 4 etc.
- Focus on pin 2: Test from 2 to 1, then 2 to 3, 2 to 4 etc.
- Focus on pin 3: Test from 3 to 1, then 3 to 2, 3 to 4 etc.
- ( etc )
Testing from 1 to 2 implies the opposite polarity compared to testing from 2 to 1, so the procedure works even if diodes are present (which I doubt, but anyway...). Note, BTW, that the "continuity" test needs to reveal values as high as 1,000 ohms. So, be sure your meter (or other apparatus) will detect a diode in series with 1,000 ohms.
Having found the first instance of continuity, release additional buttons until only one is pressed (the one whose continuity has been detected).
You've now identified one pin that you can consider to be a column and one pin that you can consider to be a row.
With this key information, the puzzle begins to unravel more quickly. You can now improvise some new test patterns to finish the job, starting by putting the focus on one of the two pins you've identified.
-- Jeff
PS- I'd stick with this approach even though, as Michael says, some switches may have their own pin. You'll sort the whole thing out eventually.
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