The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Repairs

If it used to work, it can work again

Microsoft Comfort Curve Keyboard Cleanout

Pin punch in keycap stem

Comes a time in the life of every keyboard when you must simply tear it apart to clean out the crud. I’ve been using a Microsoft Comfort Curve keyboard for several years and it’s worked well, but the grunge finally exceeded even my lax standards.

A handful of screws secures the bottom cover; the shortest screws run down the middle. Surprisingly, the giant HEALTH WARNING label doesn’t cover any screws. A row of gentle snap latches along the edges holds the covers together; ease them apart with a small screwdriver or your fingernails.

The lower cover holds the crosspoint matrix under a giant silicone rubber spring mat, with the USB interface board to the upper left. I left those in place, as the top cover captured nearly all the crud.

The keycaps have stems that slide in guide tubes molded into the top cover, with triangular latches that both secure the stem and prevent it from rotating. I used a small pin punch to push the keycaps out, as shown in the top picture; the punch much be small enough to allow the latches to bend inward as they clear the notches.

Keycap retaining latches

The larger keys have equalizing wire bails that latch under guides molded into the top cover. They’ll slide right out, but don’t shove the pin punch too far too fast.

Keycaps with equalizing wires

Many of the keycap stems have ridges along their length to ensure each one fits only in its proper position; the triangular latches also have different orientations. This view shows the numeric pad (from the “screen” side of the keyboard) with a variety of coded guide tubes, wire bail guides, and the surprisingly deep tub underneath the keycaps that may capture much of the inevitable liquid spill and route it out the drain hole near the far edge.

Keyboard top panel

I tossed the keycaps and top cover in the dishwasher, which did a wonderful job of cleaning them out. A dab of silicone grease on the wire bail contact points should keep them sliding freely.

Reassembly is in reverse order, although I defy you to put all the keycaps back in their proper places without referring to another keyboard…

2010-10-29
Kitchen Scale: Expedient Button Replacement

According to the date code on the back, we’ve had this kitchen scale for nigh onto a decade, so I suppose I shouldn’t be surprised that the molded plastic sheet over the buttons has cracked. Mary & I were in the midst of a tag-team baking session when the middle (Power) button cover went crunch and gave out.

Kitchen scale – cracked buttons

Although it’s not obvious, all three buttons are about halfway disconnected from the surface. The rightmost button has a crack nearly all the way around the perimeter.

Button covers removed

A quick encounter with a razor knife removed the entire block of cracked plastic, revealing the surprisingly off-centered button recesses. No wonder the plastic cracked!

The junkpile disgorged a thin sheet of laminated cardboard that peeled neatly down the middle. Cut it to fit the rectangle, apply a strip of Kapton tape, and it was back in action in about ten minutes… the bread dough never missed me.

Kitchen scale – expedient button cover

This was a quick-and-dirty fix to get the thing back in operation; when the Kapton tape fails, I’ll do something more permanent and less hideous. I promise…

2010-10-24
Another Bike Flat: Michelin Hair

Rode around the big block on some errands, stopped at the Vassar Farm garden to haul some squash home, rode off… and the bike handled poorly. Well, with a few dozen pounds of produce in the panniers that’s not unusual, but this was worse. Yup, another flat.

This time, however, our daughter was home and could rescue me in the van. Back in the shop, I found this obvious suspect:

Embedded glass fragment

Once again, however, this wasn’t the problem, as the tire liner was barely scuffed. Those are glass fragments inside the gash, which might actually be the same one as before.

There weren’t any other pointy objects embedded in the tire, but the tube wouldn’t stay inflated long enough to find the leak. I took the tube upstairs, submerged it in a pan of water, and found a rash of holes. Not pinholes, not a failed tube, but a series of punctures.

Steel wire fragment

Examining the tire liner revealed the cause: a strand of what my buddy DBM calls Michelin Hair poking through the tire liner. It’s a fragment of the steel belt from a car or truck tire, most likely shed from a disintegrating semitrailer recapped tire.

There is absolutely no defense against these things, because they have razor-sharp points on both ends where the wire fractured. When the tire picks one up, every rotation drives it through the rubber, the Kevlar belt, the tire liner, and the tube. The usual symptom is a slow leak, eventually followed by a row of holes in the tube as it shifts position under low pressure.

In fact, the tube had a slow leak since I installed it a few weeks ago after a tube failure. I wondered if I’d inadvertently installed a fold, but now I think I ran over this wire during the first few rides and it’s been getting worse ever since.

That tube is a goner! I installed another Schwalbe tube and we’ll see what happens; one has been working fine on Mary’s bike for the last three months.

Here’s a look at the steel wire from the side:

Steel wire fragment through tire liner

It was completely through the liner, with only a stub sticking out on the tire side. There’s certainly a matching hole somewhere on the tire, but it’ll be indistinguishable from all the other nicks and gashes.

2010-10-22
LED Flashlight Disassembly

Of late I’ve been toting an LED flashlight / laser pointer around in my pocket for peering into dark corners and highlighting interesting objects. It started flickering and I discovered the joint just aft of the switch had become slightly loose.

Disassembled LED Flashlight

Well, I always wondered how the thing came apart and now I know!

The threadlocking compound seems to have turned into dusty white powder, although my pocket doesn’t seem all that hostile an environment.

Flashlight innards

The switch assembly pulls out, revealing the LED circuit board with the laser module in the middle. The two wires correspond to the two ON states: flashlight and laser.

For what it’s worth, the 8 LEDs draw 130 mA (16 mA each), far more than the 3 mA each in that pathetic work light.

The laser draws 20 mA.

Screwed everything back together and it works fine again…

2010-10-20

X Server 1.18 vs Wacom: Back to the Mainline

As mentioned there, I had to use the Arch Linux linuxwacom-bamboo-cth-ctl package because X Server 1.8 discarded all the carefully tweaked HAL baggage and the existing xf86-input-wacom package wasn’t yet compatible with the new server.

That worked fine, until the most recent X Server tweak killed the Bamboo driver (which I hadn’t manually updated). As I expected, though, the new xf86-input-wacom package works just fine, so I can discard my manual workaround.

Having recently tweaked the tablet coordinates to keep the pointer out of the gutter, I first thought I’d killed something… but that would happen instantly, not after a while. The key was looking in /var/log/Xorg.0.log to find this gem:

[  3447.599] (II) LoadModule: "wacom"
[  3447.638] (II) Loading /usr/lib/xorg/modules/input/wacom_drv.so
[  3447.651] dlopen: /usr/lib/xorg/modules/input/wacom_drv.so: undefined symbol: dixScreenOrigins
[  3447.652] (EE) Failed to load /usr/lib/xorg/modules/input/wacom_drv.so
[  3447.652] (II) UnloadModule: "wacom"
[  3447.652] (EE) Failed to load module "wacom" (loader failed, 7)

Removing the bamboo package seems to have wiped out the udev rule that creates the /dev/input/wacom symlink. Adding that back in, as described there, solves that problem. Again.

The evidence in /var/log/Xorg.0.log looked like this:

[ 52121.754] (**) Option "Device" "/dev/input/wacom"
[ 52121.754] (EE) xf86OpenSerial: Cannot open device /dev/input/wacom
        No such file or directory.
[ 52121.754] (EE) Wacom - stylus: Error opening /dev/input/wacom (No such file or directory)
[ 52121.754] (II) UnloadModule: "wacom"
[ 52121.754] (EE) PreInit returned NULL for "Wacom - stylus"
[ 52121.754] (**) Option "Device" "/dev/input/wacom"
[ 52121.754] (EE) xf86OpenSerial: Cannot open device /dev/input/wacom
        No such file or directory.
[ 52121.754] (EE) Wacom - eraser: Error opening /dev/input/wacom (No such file or directory)
[ 52121.754] (II) UnloadModule: "wacom"
[ 52121.754] (EE) PreInit returned NULL for "Wacom - eraser"

Everything is logged somewhere: the evidence is out there!

2010-10-14

Biting Through the Bite Valve

I carry a water pack behind the seat on my Tour Easy, with the hose over my left shoulder and the valve captured by a magnetic thingie pinned to my shirt. On a recent ride I hit a substantial pothole while drinking from the tube and managed to bite completely through the miracle plastic “Bite Me” valve, mostly due to clenching my teeth in concentration rather than from the impact.

Bitten bite valve

A few days later my dim consciousness finally took note that the water kept draining down into the pack between sips: every sip came with a mouthful of air.

A year or so ago, the original valve developed a nasty case of embedded gunk and I picked up a quartet of Genuine Nalgen valves (or a credible imitation thereof) from the usual eBay supplier. I wonder if the reservoir and tubing will outlast the remaining two valves?

2010-10-09
Plastic Screw-top Flashlight Fix

As part of my clear-off-the-workbench effort, this flashlight emerged from the dark depths. It’s a few decades old and wasn’t a good design: the “switch” is a simple contact between the end of the cell casing and the reflector rim, activated by screwing the reflector tighter on the case.

Broken flashlight case

The failure is simple: the case cracks through at the stress raiser formed where the “switch” contacts rest on a sharp inside corner. That stiff little spring maintains pressure on the cells, so the case is always under tension and eventually fractures.

Flashlight clamped in mill

I grabbed the broken pieces in the lathe, turned off the fractured plastic, and wound up with a pair of nicely mating surfaces (and a somewhat shorter flashlight, but it’s still long enough). Apply enough Plastruct solvent glue to soften the new faces, then clamp them together. The big manual mill knows how to apply a strong, steady vertical force to a project like this.

It’s once again hanging by the basement door, where it gets used roughly once every other blue moon (yeah, it’s color-coordinated). This isn’t the first time this flashlight has failed that way, but it’ll be the last: next time, it’s in the trash.

Honest, I swear it!

2010-10-08