deskthority

Hello Folks...
The left Alt key on my keyboard completely suddenly stopped working a few days back.
I realized it immediately because I use Alt+Tab for switching windows all the time.

I bought this keyboard in Sep 2012, so its has seen 3+ years of use.
Are such key failures normal/expected in this time frame?

I opened the keyboard and I tried to measure the resistance across the switch terminals with a multi meter and noticed that the switches that work register around 0.3 ohm (or less) and this broken switch registers a varying amount anywhere from ~6-14 ohms. I also looked at the contacts closely and tried following the traces from the broken key, but could not see anything obviously wrong.

Any suggestions on how to debug the problem and perhaps fix it?
I have a soldering iron, and multi-meter at my disposal.

This is a frosty flake CM Storm QFR with cherry brown switches.
The switches seem to be clipped to a steel plate and then soldered to the PCB.
The broken key is labeled Alt_L in the bottom row on the attached image.

To determine whether the problem is the PCB or switch, short the pads on the PCB and see if an alt keypress is triggered. If so, it might just be a dodgy switch. If that's the case, you can probably desolder the single switch and replace it. I just did this with several switches in an Apple board and it worked fine. Be very careful if desoldering the switches, I've heard that QFR pads are VERY EASY to lift off of the PCB by accident.

Thanks Scottc!

Shorting the switch pads did not trigger the key either. I verified that other keys were triggered by shorting.
So I am guessing that it could either be the pcb trace or badly soldered pad. Perhaps even a diode?

The frosty flake firmware header files were helpful to figure out row column mapping:
https://github.com/BathroomEpiphanies/c ... s/common.h

The PCB trace for column C going from the l-alt key to the r-alt key had problems. Fixed it by using a wire to bypass it.
L-Alt was the last key on that column because of which no other keys were affected by this issue.

Goes to highlight that PCB and soldering quality is very important to ensure a long happy life for a mechanical keyboard.