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Number Key Pad Types Key Pressed and Key to the Right of Key Pressed


Friend bought some mechanical keyboard from aliexpress called sunsonny. I couldn't find much information thru my searches. On the number key pad portion of the keyboard, when the "num lock" "7" "4" "1" or "0" key is pressed the number appears plus the key next to it. For example, if I press "num lock" then the number lock will turn on/off and it will also type the "/" character. If I press the "7" key, then I get the 7 character and the 8 character. If I press the "0" key, then I get the 0 character and the windows calculator opens. On the PCB if I touch the two pins of each key, I get the same results and get two characters. However I noticed when I set my multimeter to test for OHMs and then I touch the two pins then I the correct number and it does not give me two characters. Any idea how to fix this?

You could try replacing a switch, which seems like it wouldn't do anything.  More than likely, it has a software fault. If it has firmware you cannot replace, you should return it order a new one. There are some pretty good YMDK numpad kits on aliexpress

I really doubt this is a f/w issue. Notice that the affected keys are all in one column..

My first guess is that this is a hardware problem - defective, misplaced or missing component, or a fault on the board itself - shorted or broken trace, etc.

See which components / traces are common to those affected positions, and test them out.

Btw, your comment about the proper behavior when using the meter..

When you short the padsow, any & all available current will flow. When it's done with the meter (on Ohms function) the meter behaves as a current source - it applies a voltage of its own, but total current is limited by the internal resistance that was designed into the meter  for that particular range.

I wonder if there is a resistor of the wrong value somewhere on the PCB? Just one possibility!


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