Fixing a broken scroll switch


A while ago I felt I needed to upgrade my work mouse to a higher resolution one, since I am mousing all around doing designs across 3 screens. In a purchase of impulse, I ended up getting a wireless one for a good price, the 4000dpi Mpow Dragon Slayer gaming mouse. I was happy with it for the first 2 months: 2-3 weeks of life at max resolution using rechargeable batteries without lights and an excellent match for my hand. Then the scroll started working improperly, it would change direction every few steps.

Update: the thing does not work, again. I suspect it really is a bad encoder. I tried to replace it, but the size I got was incompatible so I ended up sending it to the dumpster. Not recommended.

Fixing it

I thought the problem was not mechanical – bad contact, but since I did not have a spare scroll switch anyway nor time to invest in looking for a replacement…i thought i could try an electronic fix: de-bouncing the switch, which I saw no trace of being implemented on the PCB in a brief search. Cheaper de-bouncing is normally done in firmware, without passives, however if insufficient, I can compensate in hardware.

Here is the guilty switch, the one with the red part

DSC_6580The solution: add 2 1nF capacitors across the switches. I figured this would give a good de-bounce time with what looks like internal pull up resistors (~10…100KΩ) from the microcontroller.

DSC_6581And the terrible soldering job

DSC_6581-2Then I put it back together


DSC_6586Of course, opening it meant removing the feet, which don’t stick back properly



All done, the rodent is happily and properly working. Time will tell if this will last long enough, I will update if it breaks again. I hope the engineers at Mpow can see this and fix this really great mouse. Also a more “business” model would be great. The fact that the problem shows up so soon and for so many people tells me it is a software problem – not enough debouching. It only works while the switch is perfect. I have used plenty of mice so far and never found this to be an issue ever, even for much cheaper products.

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