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

Ersatz Library Card

The rather battered library card on the bottom has been rattling around on Mary’s keyring since late in the last millennium:

Library card tags – front

I made the one on the top as a replacement, because Mary wanted one, but the library no longer issues keyring cards these days.

The front surface was laid out in The GIMP, inkjet-printed on good paper, cold laminated, laser-cut with LightBurn’s Print-and-Cut process, then affixed to the acrylic tag with really good double-sided tape:

Adriance Card – LightBurn PnC layout

I cut and applied the tape after cutting the tag, but the next time around I’ll apply the tape to the stock and cut both together to improve the edge alignment.

The rear surface data is engraved directly into the same Trolase laminated acrylic I used for the plant tags:

Library card tags – rear

The smaller text uses dot mode and the bars & number are engraved:

Library card tag – detail

In retrospect, it’s painfully obvious the engraving passes should run parallel to the bars, rather than perpendicular to them.

The barcode uses Codabar encoding generated with a Codabar font. I scaled the graphic block slightly larger than the original in the hope of making it more readable.

I determined the start and stop characters by trial and error; for this card, they’re A and B. Which could, perhaps, stand for Arlington Branch, but might equally well be coincidence.

It worked perfectly on the first scan at the library counter and apparently went entirely unnoticed. I trust duplicating a library card does not constitute a federal offense.

For what should be obvious reasons, however, I’m not posting the LightBurn layout.

2023-01-04
Kitchen Knife Handle: Epoxy Patch

The black plastic-like substance molded around the tang of our daily driver kitchen knife crumbled away near the blade and eventually reached the point my thumb couldn’t stand it any more. Given the good results of the JB Weld coating on the cheese slicer (which is still going strong after four years), I chipped away the loose fragments on all sides, wire-brushed the crater with alcohol, and filled it with epoxy:

Kitchen knife handle – tape reforming

The Kapton tape bridges the solid part of the handle with the metal just behind the blade, holding the epoxy in more-or-less the right shape while it cured overnight. The other side looks much the same, which is why I couldn’t just let it sit out.

A few minutes with a file and wire wheel knocked back the high spots and left it looking much better than before, if a bit scuffed:

Kitchen knife handle – restored

The tang inside the molded shell is kinda-sorta cruciform, with an exposed rib along both sides. I think the plastic shrank around the tang in that gap between the ribs and the blade, where its lack of flexibility caused the cracks.

Neither a beautiful restoration nor a permanent fix, but it ought to last for a while. Similar cracks at the hilt end of the handle suggest more repairs lie in its future.

2022-12-30
Toilet Valve Mystery

Last week Mary reported the toilet in the front bathroom had the sound of running water, which is unfortunately the sort of noise I can no longer hear. I replaced the flush (a.k.a. “flapper”) valve, because it’s always the flush valve, cleaned the valve seat, washed my hands vigorously, cauterized both stumps, and declared victory.

This week she reported it was once again leaking.

A bit of poking around showed the tank was now full to the top of the overflow pipe and the refill tube was piddling down the pipe: obviously, something was wrong with the fill valve, because the flush valve was sealed tight.

Having been through this rodeo a few times, I fetched a replacement valve disk from the Box o’ Toilet Stuff, installed it, and was about to declare victory when I noticed the refill tube was still piddling.

Pop the top off the fill valve and peer inside:

Toilet Fill Valve – aligned

Did you see it? I didn’t, either, when I replaced the valve disk.

More fiddling produced this view:

Toilet Fill Valve – cracked

The valve seat is attached to a plastic stem going down the length of the fill tube, but it’s free to rotate on both ends. I have no idea what applied enough torque or how it could break all those ribs, but there they were(n’t).

Fetch a complete valve kit from the aforementioned Box, drain the tank, install All. The. Parts., verify that the valve now shuts off properly, declare victory, etc, etc.

Whereupon I could switch caps and begin making the weekly pizza.

Never a dull moment around here …

2022-12-20
Sears / Kenmore Progressive Vacuum Cleaner: Motor FAIL

After seven years, our Sears / Kenmore Progressive vacuum cleaner gave off a horrible screech and an intense smell of electrical death, prompting me to tear it apart.

It’s easy to find the two front screws holding the top in place, although you’ll need either a bendy or offset screwdriver to remove them:

Sears Progressive Vacuum – front case screws

Pull up hard on the cord retraction plunger to remove it, revealing the two rear screws:

Sears Progressive Vacuum – rear case screws

Extract the wires and motor control PCB from their niches:

Sears Progressive Vacuum – motor assembly overview

Prying the latch in the middle of the rear panel (over on the right) releases the motor assembly, which you can then wiggle-n-jiggle upward and out:

Sears Progressive Vacuum – extracting motor assembly

Disconnect the wires, peel off various foam bits, and extract the motor from its carapace. Measure the blower diameter and cut a suitable plywood clamp for the bench vise:

Sears Progressive Vacuum – custom motor clamp

I loves me some good laser cutter action, even when the plywood crate the laser came in doesn’t have much to recommend it:

Sears Progressive Vacuum – failed plywood clamp

I vaguely recall reading the purple tinge comes from the bromine vapor used to dis-insect the wood during manufacturing, before shipping it halfway around the planet.

One area of the commutator looks like it’s in bad shape:

Sears Progressive Vacuum – as-found commutator

Clean the commutator bars in the desperate hope it’s just random crud, even though that seems unlikely, then connect a widowmaker cord to the motor terminals:

Sears Progressive Vacuum – widowmaker line cord

Use a Variac to spin the motor at a (relatively) low speed while watching the brushes and commutator:

Sears Progressive Vacuum – commutator sparking

Now, that is not a nominal outcome.

The cleaned commutator again shows signs of distress:

Sears Progressive Vacuum – scarred commutator

Indeed, measuring the resistance across the line cord terminals shows a shorted winding: 0.0 Ω with the brushes aligned on the bars just antispinward of the scars.

So the motor is definitely, irretrievably dead.

Extracting the brushes shows the arcs have eroded their spinward edges:

Sears Progressive Vacuum – eroded motor brushes

The dark smudge on the windings seems due to internal problems, rather than just the arcs, because the wiring crossing between the commutator and the smudge remains clean:

Sears Progressive Vacuum – charred motor windings

One can buy a used motor assembly on eBay for about $40, with no assurance it doesn’t also have a shorted winding.

Dang, now I gotta make more adapters for whatever vacuum comes next …

2022-12-08
Thermador In-Wall Heater

Our house dates back to 1955 and features several fancy items not found in contemporary dwellings. Take, for example, the Thermador in-wall heater in the front bathroom:

Thermador In-Wall Heater

It has a finger-friendly design apparently intended to admit a small finger through the grille, where it can easily contact the resistance heating coil, so while we were moving in I snapped a GFI circuit breaker into that slot in the breaker panel. We advised our (very young) Larval Engineer of the hazard and had no further problem; as far as I know, that breaker never tripped and no fingers were damaged.

Back then, while adding that breaker and cleaning the first half-century of fuzz out of the thing, I evidently blobbed silicone rubber on the screw terminals of the switch:

Thermador In-Wall Heater – switch contacts

They don’t make switches like that any more.

For reasons not relevant here, we’ll be using it for the first time since we moved in, so I spent a while cleaning / blowing / brushing another two decades of fuzz out of it.

Minus the fuzz, the heater no longer smells like a house on fire:

Thermador In-Wall Heater – glowing

If that doesn’t warm your buns, nothing will!

2022-11-30
Numeric Keypad Repair

Having set up a cheap wireless numeric keypad as a simple macro pad at my left hand, I eventually knocked it off the desk, whereupon the screw compressing the back of the case against the membrane switches ripped through the plastic:

Numeric Keypad – compression screw pullout

The symptoms came down to erratic operation of a few keys that became worse as I continued tapping on the thing. Finally, with nothing to lose, I took it apart and, upon seeing the hole in the case, realized I didn’t have to cut the usual label to find the hidden screw.

Slathering the little donut with acetone and clamping things together might work for a while, but I’m sure the keypad will hit the floor again with similar results.

Instead, recruit some candidates from the Box o’ Random Screws:

Numeric Keypad – screw selection

Pick the screw big enough to grip the undamaged boss on the front of the case, yet short enough to compress the back again, add a small washer spanning the hole, and it’s all good again:

Numeric Keypad – screw installed

This only works because the keypad sits at enough of an angle to hold the screw off the desk.

That was easy …

2022-11-25
Epson ET-3830 Duplexer Paper Jam

For the record, it is possible to get a piece of paper jammed so far inside the duplexer rollers in the back of an Epson ET-3830 Multifunction Printer / Scanner that it is not only completely invisible from the inside, but that it cannot be removed without disassembling the duplexer:

Epson ET-3830 duplexer jam

It jammed while attempting to print another batch of Geek Scratch Paper with a semilog grid, without actually duplexing the sheets. The specs say the printer can handle 4×6 paper, so I assumed 4.24×5.5 paper would be Close Enough. Apparently not.

Print ’em two-up, chop the sheets down the middle, pad and glue, and it’s all good:

OMTech CO2 laser power supply – bandwidth tests – semilog graph

2022-11-22