Mica Compression Capacitor: Unsolderable Pins

The mica compression capacitors have a finish on the pins that turned out to be completely un-solderable:

Mica compression capacitor - solder vs pin

Mica compression capacitor – solder vs pin

Some casual searching suggests this is a problem with sulfur contamination of the tin-lead solder layer. I can’t vouch for any of that, as the flat areas forming the capacitor seem to be silver-plated, but …

After some flailing around, I completely disassembled the capacitor, applied 800 grit sandpaper to remove all of the solder / flux / corrosion / tarnish / surface plating from the pins, dabbed on some RMA flux, then applied a thin layer of solder to both sides. Fortunately, the capacitor could be disassembled; they don’t make ’em like that any more.

The solder layers must be thin, because the slots in the ceramic base must pass two or three pins apiece: four or six solder layers add too much thickness. Solder-wick is my friend!

For reference, the 700 pF side looks like this:

Mica compression capacitor - 700 pF disassembled

Mica compression capacitor – 700 pF disassembled

The steel washer does not have a mica washer underneath (as does the washer on the 400 pF right side). The two grayish steel plates go on the top.

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Insouciant Squirrel

Squirrels spend most of their time on all fours and, when they do pop up for a look around, generally seem hunched forward, ready to drop-and-run.

Not this critter:

Squirrel leaning back

Squirrel leaning back

Definitely brandishing a big leaning ‘tude


Improvised Repairs Done Wrong

Mary’s relatives encountered this repair in a rental flat during Thanksgiving week:

Door handle - hex head bolt

Door handle – hex head bolt

Don’t have a hex bolt with the right thread? No problem: just use a sheet-metal screw, perhaps with a self-drilling point:

Door handle - metal screw

Door handle – metal screw

Those hex heads let you apply more torque with less risk of stabbing yourself in the palm, which strikes me as an all-around Good Thing. I prefer socket-head cap screws, myself, but I’ll admit they’re an acquired taste.

I’d like to think I wouldn’t do that …


J5-V2 700 lm Flashlight: QC FAIL, Redux

The inside of the replacement J5 V2 Tactical Flashlight doesn’t have quite as much dirt on the LED emitter, but it’s still pretty bad:

J5-V2 Flashlight - LED crud - second unit

J5-V2 Flashlight – LED crud – second unit

The small white dingus at about 10 o’clock seems to be a plastic shred stuck on end to the emitter lens. Here’s a better look, rotated a quarter-turn counterclockwise:

J5-V2 Flashlight - LED crud detail - second unit

J5-V2 Flashlight – LED crud detail – second unit

There’s also an alien egg glued to the heatsink beside the LED:

J5-V2 Flashlight - random pellet - second unit

J5-V2 Flashlight – random pellet – second unit

I’m hoping it’s another random plastic blob.

There’s no point in returning this one; it’ll suffice for my purposes. However, given two random samples, I’d say the J5 Tactical Flashlight factory, wherever it may be in China, is really filthy.

I’d hoped that paying a bit more for a “tactical” flashlight, instead of going bottom dollar, would yield a better product. Maybe it did?


Monthly Science: Bottled Water Evaporation

These emerged from a hidden corner of a basement shelf, where they’ve been sitting undisturbed for far too long:

Bottled Water Evaporation

Bottled Water Evaporation

I’ve known for a while that the PETE plastic used for nearly all bottles isn’t completely waterproof, but never had occasion to measure the results.

The laser-etched date code  on the bottles says they “expired” in late August 2012, so, assuming one year of shelf life, they’ve been quietly evaporating for five years.

Sampling a few bottles shows a nearly uniform weight of 459 g. A drained bottles weighs 13 g, so let’s say the bottles now contain 445 g of water. They should start out with 500 g, although I’d be mildly surprised if it wasn’t a bit over that to prevent some dork from complaining about getting only 498 g.

Rounding in all the right directions, losing 60 g during five years works out to a tidy 1 g/month in a basement room at 60% RH.

The surface area of those wonderfully convoluted bottles might be 300 cm², so they lose 3 mg/cm²·month.

They’re near enough to 0.10 mm thick, which I’m sure is a compromise between reducing weight (and, thus, plastic cost) and incurring messy failures during normal handling. The evaporation rate surely varies as an inverse exponential of thickness, but I’m not going there.

I’m certain water bottlers know those numbers to several decimal places and can plot them versus all the interesting variables.

Memo to Self: don’t lose track of the water bottles!


Amazon Packaging: Lack Thereof, Redux

Fortunately, it’s hard to damage an aluminum-body “tactical” flashlight:

J5-V2 Flashlight - Amazon packaging

J5-V2 Flashlight – Amazon packaging

A keyboard and cylindrical cell charger arrived intact, with absolutely no credit due to Amazon’s careful packaging:

Keyboard and charger - Amazon packaging

Keyboard and charger – Amazon packaging

Sometimes, a box does arrive with a token scrap of padding dropped inside, but, as nearly as I can tell, it’s cheaper for Amazon to replace the occasional damaged item than to waste time and material stuffing the boxes with air pillows, eco-foam peanuts, or, heaven forfend, space-filling foam.


Kenmore Progressive Vacuum Tool Adapters: Second Failure

Pretty much as expected, the dust brush nozzle failed again, adjacent to the epoxy repair:

Dust brush adapter - second break

Dust brush adapter – second break

A bit of rummaging turned up some ¾ inch Schedule 40 PVC pipe which, despite the fact that no plumbing measurement corresponds to any physical attribute, had about the right OD to fit inside the adapter’s ID:

Dust brush - PVC reinforcement

Dust brush – PVC reinforcement

The enlarged bore leaves just barely enough space for a few threads around the circumference. Fortunately, the pipe OD is a controlled dimension, because it must fit inside all the molded PVC elbows / tees / caps / whatever.

The pipe ID isn’t a controlled dimension and, given that the walls seemed far too thick for this purpose, I deployed the boring bar:

Dust brush adapter - reinforced tube - boring

Dust brush adapter – reinforced tube – boring

That’s probably too much sticking out of the chuck, but sissy cuts saved the day. The carriage stop keeps the boring bar 1 mm away from the whirling chuck.

Bandsaw it to length and face the ends:

Dust brush adapter - reinforcement

Dust brush adapter – reinforcement

The PVC tube extends from about halfway along the steep taper from the handle fitting out to the end, with the section closest to the handle making the most difference.

Ram it flush with the end:

Dust brush adapter - reinforced tube - detail

Dust brush adapter – reinforced tube – detail

I thought about gluing it in place, but it’s a sufficiently snug press fit that I’m sure it won’t go anywhere.

Natural PETG probably isn’t the right color:

Dust brush adapter - reinforced tube - installed

Dust brush adapter – reinforced tube – installed

Now, let’s see how long that repair lasts …

The OpenSCAD source code as a GitHub Gist:

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