deskthority

I have a keyboard with Alps SKCM switches in it. It was in decent condition when I got it, just a little dusty.

I have been working on restoring and converting this board. I've desoldered all the switches and ultrasonic'd the sliders and switch tops. Now everything is all back together.

When I started working to convert it (controller replacement), I found that 2 switches appeared to be dead. I replaced those switches with working ones and proceeded.

I finished converting the board. I tested it a few times to make sure the keymap was correct and all keys registered.

Then I set it aside for a while, returning to it today after about a week or two. I was doing more QMK tweaks, playing around with different features that I've been meaning to try out. In the process of all this, I found that a couple of keys were not working. Then I found a couple more. And a couple more. etc.

I first thought that maybe I messed something up with the firmware so I tested each "dead" switch with a multimeter and, YES they are indeed truly dead. I also tested to make sure that the matrix would pick up a real switch-pressing using a pair of tweezers.

My theory (which is probably stupid) is that the board sat frozen in time for decades not getting used. Then over time getting covered in dust. I didn't ultrasonic the switchplates so those probably had dust/dirt on them. Maybe using the keyboard after all these years knocked some gunk loose?

The contacts corrode. Try pressing keys down and wigging so as to exercise the crosspoints. Surface corrosion comes off with exercise. You can try electronic contact cleaner, it's often just isopropyl alcohol and propellant.

XMIT wrote: 27 Aug 2019, 03:24 The contacts corrode. Try pressing keys down and wigging so as to exercise the crosspoints. Surface corrosion comes off with exercise. You can try electronic contact cleaner, it's often just isopropyl alcohol and propellant.

What he said, while the switch is still assembled, pull up on the slider and move it forward, backwards, left, and right while actuating the switch to simulate off-center keypresses. If that doesnt work then open the switch and make sure the switchplate is making contact with the leaf spring. Last resort would be to ultrasonic clean the switches. Had to do this with my Focus 555 and was a pain in the ass and took me a couple hours of trial and error, but it works.

Right now I'm frustrated. Not because this is a particularly big task, but because I don't know how/why it happened in the first place.

I'm even more frustrated that my nice new desoldering iron didn't come with a tip sized for Alps pins (I know, how dare the manufacturer). This is compounded by the fact that most of the solder joints are only "half" soldered (i.e. do not form a nice peak). So pair those two facts together and you get a recipe that equals some desoldering work that doesn't actually work. What I'm having to do is add more solder to each pin, just to then unsolder it two minutes later. It's madness!

But where there's frustration, there's also an opportunity to make a slow motion macro video. And I just cant pass something like that up.

Here is a clip that demonstrates just exactly what I'm talking about.

snacksthecat wrote: 02 Sep 2019, 19:26 Right now I'm frustrated. Not because this is a particularly big task, but because I don't know how/why it happened in the first place.

I'm even more frustrated that my nice new desoldering iron didn't come with a tip sized for Alps pins (I know, how dare the manufacturer). This is compounded by the fact that most of the solder joints are only "half" soldered (i.e. do not form a nice peak). So pair those two facts together and you get a recipe that equals some desoldering work that doesn't actually work. What I'm having to do is add more solder to each pin, just to then unsolder it two minutes later. It's madness!

But where there's frustration, there's also an opportunity to make a slow motion macro video. And I just cant pass something like that up.

Here is a clip that demonstrates just exactly what I'm talking about.

I almost always add fresh solder when desoldering a board. I've been working on PC boards for well over forty years now, and it's just something I do.

If you've ever seen a wave soldering machine in use on a PC board assembly line you'd be amazed that it works at all. Basically you have a flat bowl of molten solder, which rocks slowly back and forth, creating a wave, which washes across the bottom of the board, and sticks to anything metal that isn't masked off. The board is pre-fluxed, and bar solder is continually added to the mix (usually by hand) as the solder is used up. There's always a bunch of crud floating on top--old flux, impurities in the solder, and whatever else falls into the mix. Adding fresh solder (rosin core) will almost always give a faster and cleaner desoldering result because it flows better than the old crappy mess from the original wave soldering job.