[solved] keys jittering...

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Eszett

21 Aug 2018, 20:43

Hi makers! On my recent build I have some keys "jittering", to be more specific only those keys in row6 and row7. I replaced all diodes in these rows by new ones which unfortunately didn't solve it. Does someone have a clue what could be the issue here? Here I'm trying to visualize my problem:
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jitter.png
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Last edited by Eszett on 02 Sep 2018, 12:50, edited 1 time in total.

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vvp

21 Aug 2018, 20:54

It does not look like a diode problem. It looks like you have a intermittent short between row6 and row7 wires. Or a fixed resistance between those wires is not infinite but around the pull(up/down) resistor resistance.

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Eszett

21 Aug 2018, 21:13

vvp! Alright, I checked the pins of the Atmega with a microscope but couldn't see any suspicious solder lumps which could create a bridge. However, I took my soldering iron and reflowed the solder joints anyway. God in heaven, that solved it! The lesson I learned is, that I can't even trust my 300x microscope, since lumps may hide between the pins at spots and angles where my magnifiers/microsopce can't see. My alternate theory is, that I forgot cleaning with Isopropyl (yes, I did), and little solder paste balls created a semi-bridge between the pins? Can that be? Anyway, keyboard hail! :idea:

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Darkshado

22 Aug 2018, 06:33

Isopropyl would be good for excess flux, not so much for bridging. I haven't done much surface mount yet, but one trick I'd suggest is using soldering wick on top of the contacts to remove excess solder and potential bridges.

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vvp

22 Aug 2018, 09:24

If it was SMD then it could be some soldering paste which was not melted and created a (high resistance) connection between the two pins. Or it could be other things. Hard to tell without detailed pictures. And even with the pictures we just may not know.

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Eszett

02 Sep 2018, 12:48

Ah alright... now. Marked the thread as [solved]

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