First time I seem to have actually broken a keyboard, and it’s my favourite one, Leopold FC750R. What happened is that I spilled a drink on it yesterday and now 5 keys don’t work. After testing it seems that a whole cluster of diodes seem to be broken. I’ve measured with diode-test on multimeter, continuity says that the keys themselfs are fine. However I swapped one working diode from another place and that didn’t work. Could it be that a mcu pin is fried ? how to check ? The image below is
from the broken diode cluster.
Could be a long shot, but use a q-tip soaked in iso alcohol to clean around the diodes. It is possible that the residue from what you spilled is causing the diodes to electrically connect with each other.
Fried IO pins are unlikely I think.
I think water spillage made more damage than the diodes, and most probably some vias have been destroyed in the process, breaking traces between diodes and CPU.
See the VIA near D55 ? Think that the problem is there.
I see no VIAs for D60 to D63, maybe replacing the diodes here will solve the issue for the four switches they are connected to.
As for D53 and D55 (I suspect you tried to replace one of those diodes) you’d need to check were the traces are going from and to the diodes (and by the vias).
You may unfortunately desolder all the switches to have access to the other side of the PCB
Good luck !
If you have any cameras with an IR mode or have access to a thermal camera through a local shop or school, those can be useful for spotting bad components, which tend to be much hotter under power.
It’s nearly impossible to damage diodes in keyboard PCB with spillage because they enclosed and quite resilient to corrosion. Sorry but I’d doubt your diode tester, have you confirmed other diodes working with it?
The most often the victim of spillage and following corrosion are the vias (those tiny connections to the other side of the PCB). Therefore best course of action now is to follow common track for row 5 all the way to the MCU with continuity tester.
Sorry but this is pointless with partially working keyboard even if diodes are shorted there will be no increased heat. Pretty much the same for MCU which could be only partially faulty and therefore will not show much increased heat to make any judgement from it.