Chosen Solution
Hello ! Once upon a time, a friend gave me this keyboard, that was not working properly since day 1, and he got it replaced but they did not asked the failing keyboard back. So I’d like to repair it to give it to a friend with a lame keyboard. This is a mecanical keyboard, here is all the references I can give you : https://www.ozonegaming.com/product/stri…
There is some kind of short circuit between key " 3 " and " 4 “, meaning that when I type either of theses, both fires. So far I tried to de-solder both and re-solder them and checked with a continuity test that there was a indeed short between the keys. There was no visual problem with the cherry MX switches that I re-soldered and no visual problems on the other side of the board either. But I may be wrong (?). Here is a picture of the logicboard centered on keys " 3 " and " 4 “.
Here is a close up shot of the traces of the PCB on failing keys :
And there is a close up shot of the traces of the PCB on normal keys :
I have solder and electrical tools but I’m “short” ( ;) ) on ideas on how to fix it. Thank you for your time ! Edit 07/03/17 : I tried to de-solder the diode you asked me to test and I’m having difficulties to pry it out. It feels like I would need to heat it more but I am afraid I might kill the diode in the process. Still I can confirm that it’s soldered on a pad and not in a " hole " since I can observe some other places where there is no key and where there’s still a key slot with all the pads and mounting holes. How to you feel about it ? Also the more I think about it, the more I wonder why we should do that. The only anomaly we found yet, never seen on other keys is on the 2 big pads on this picture :
Hi @whitelight , Prove that there is conductivity in one direction only through the diodes i.e. top to bottom in each diode. If none reverse the meter leads and test again as diodes only conduct in one direction. Compare good ones as you did before to make sure it is the same. I’d carefully remove the diodes as the tracks seem to go under them both and check for solder bridges or some other connection between the 2 diodes at the bottom end. Check if there is still a connection between 3 and 4 with the diodes removed. Update (03/07/2018) Hi @whitelight , What is it that is highlighted in the green circle? Is it a solder splash across two tracks?
(click on image to enlarge for better viewing)
