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  1. #1
    Newbie level 1
    Points: 17, Level: 1

    Join Date
    Jul 2019
    0 / 0

    Possible water damage inside keyboard

    Canít find an appropriate answer so far. Spilled water on kb last week. Unplugged and dried. Kb was fine for 2 days, then all the far left buttons stopped working as well as the number pad 7. Tried drying twice more to no avail. Thought Iíd test the circuit with my multi meter but I have no clue to what Iím doing. Iíve cleaned all areas and removed some minor oxidation. Can someone tell me what and where I should be testing for voltage etc. Iíve attached a picture of the effected side of the pcb. I have solder and cold solder equipment.

    Thanks in advance.

    Click image for larger version. 

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  2. #2
    Super Moderator
    Points: 52,942, Level: 56

    Join Date
    Apr 2011
    Minneapolis, Minnesota, USA
    2580 / 2580

    Re: Possible water damage

    Your photograph has labels on the pcb telling what a key does (ctrl, alt, cap, tab, z, a, q, etc.). It's not clear what is the mechanism that makes contact. Is it a switch, or magnetic sensor, or a conductive pad touching copper or graphite traces?

    Did you see whether liquid got into the faulty keys individually, causing corrosion/ shorting/ loss of contact, etc.)?

    Or there is the possibility that a copper trace went bad (shorted, disconnected, etc.) affecting several keys. The keyboard is read via a grid arrangement of wires. Knocking out one wire causes a misread of all keys which depend on that wire. So if a single thin trace goes open or shorts, then that could cause a misread of many keys.

    - - - Updated - - -

    At LD25 there is some discoloration. Nearby traces appear extremely thin and close together. Just a bit of corrosion could create a hairline break.

    See if you can determine whether a trace has a hairline break.
    It's best not to apply more than a couple volts from an ohmmeter or power supply, and even then it should be through a high-ohm series resistance.

    If you can find suitable test points to measure voltage changes, and press the keys, then you may discover a pattern of behavior about keypresses and voltages on the pcb. This could be tedious. It would be easier if you could compare it with a good keyboard. But to troubleshoot your keyboard you need to find what makes the difference between working keys and faulty keys.

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  3. #3
    Advanced Member level 5
    Points: 17,237, Level: 31
    7 years registered

    Join Date
    Nov 2012
    777 / 777

    Re: Possible water damage inside keyboard

    Kb was fine for 2 days, then all the far left buttons stopped working...
    That suggests corrosion. There were some dissolved solids in water and when the water left, they stayed back and did their work over two days.

    You need to hunt over with a small magnifying glass. Water has a tendency to go underneath various components and you may need to scrub gently with a used toothbrush.

    I presume that the round white plastic objects are the actual keys. If they can be removed, remove and clean the contacts. Also clean the conducting rubber pads.

    Try cleaning the board with isopropyl alcohol. That should not damage any of the plastic parts.

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