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

Screw Cutting Fixture vs. Lathe Ways
A length of aluminum hex bar became a nice 10-32 screw trimmer:

Screw cutting fixture – 10-32 – first cut

The hex neatly fits a 5/8 inch wrench, so I can tighten the jam nuts enough to run the lathe forward, part off the screw, and clean up the end just fine.

Unfortunately, the second test cut didn’t work nearly so well:

Screw cutting fixture – 10-32 – wrecked

With the cross-slide gib adjusted to the snug side of easy, the cut put enough pressure on the parting tool to lift the way on the tailstock side about 4 mil = 0.1 mm. The parting tool submarined under the cut, dislodged the fixture, and didn’t quite stall the motor while the chuck jaws ate into the aluminum.

Well, that was a learning experience.

After tightening the cross-slide gib to the far side of hard-to-turn:
- Put a longer screw in the fixture
- Grab it in the tailstock drill chuck
- Crunch the hex end of the fixture in the spindle chuck
- Remove the screw through the spindle (*)
- Put a slight taper on the end of the fixture threads with a center drill
- Deploy the live center to support the fixture
Like this:

Screw cutting fixture – 10-32 – rechucked

Turns out that angling the bit by 10° dramatically reduces chatter. If I had BR and BL turning tools, I’d be using them with the QCTP set to 0°, but they weren’t included in the set that came with the lathe.

It’s a good thing I’m not fussy about the diameter of that cylindrical section:

Screw cutting fixture – 10-32 – reshaped

I knew the craptastic lathe ways needed, mmmm, improvement and it’s about time to do something.

(*) By concatenating all my ¼ inch socket extension bars into an absurd noodle capped with square-to-hex adapter holding a Philips bit.
2017-02-17
Cheap WS2812 RGB LEDs: Continuing Failures

Three more knockoff Neopixels failed in the last few weeks, including one that can’t possibly suffer any thermal stress:

Halogen bulb brass cap – overview

I wrapped the halogen bulb in a shop towel, laid the ersatz heatsink against an anvil (actually, it was a microwave transformer on the Squidwrench operating table), whacked a chisel into the epoxy joint, and met with complete success:

Failed WS2812 LED – ersatz heatsink

Having epoxied the PCB and braid in place, there was nothing for it but to drill the guts out of the brass cap:

Failed WS2812 LED – drilling

Which produced a pile of debris in addition to the swarf:

Failed WS2812 LED – debris

The brass cap emerged unscathed, which was just about as good as I could possibly hope for.

The base LED in this 21HB5A also failed:

21HB5A on platter – orange green

Soooo I had to unsolder the plate lead and Arduino connections to extract the bottom PCB; fortunately, that was just a press-fit into the base.

I should mount a 3.5 mm stereo jack on the platter and run the plate lead into a nice, albeit cheap, knurled metal plug, so I can dismount both the tube and the plate lead without any hassle. Right now, the tube can come out of the socket, but the plate lead passes through the platter.

For whatever it’s worth, all of the dead WS2812 LEDs pass the Josh Sharpie Test, so these failures don’t (seem to) involve poor encapsulation.

2017-02-13
X10 Transceiver Case Plastic: End Of Life, Redux

Another X10 RF transciever, this one made for IBM (!) a long time ago, emerged from the heap with its case falling apart: the plastic bosses that should anchor the screws had broken off, then cracked radially. Given that I was probably going to toss it anyway, for reasons that will soon be obvious, I tried repairing the bosses just for practice.

Stuffing the boss fragments into close-fitting brass tubes, with a dash of IPS #3 on the broken faces, put them back together reasonably well:

HD501 X10 Transceiver – plastic boss gluing

More IPS #3 and a pair of clamps stuck the bosses back on the case:

HD501 X10 Transceiver – plastic boss assembly

Note the dark smudge on the inside of the case. Even though nothing on the PCB looked particularly overheated, Soot Is Sign of Bad Electrical Health.

And it turned out neither the bonds nor the plastic were up to the task. A day after successfully reassembling the transceiver, the bosses failed along new cracks and crumbled into different fragments.

I applied a Kapton tape belly band around the case halves, verified that the transceiver no longer produced reliable X10 commands, and executed ++recycle_pile.

So it goes.

2017-02-12
Kenmore Progressive Vacuum Cleaner Carpet Brush Disassembly
The beater bar found and ingested a remarkably long strip of carpet yarn, resulting in a sudden stop and an acute need for disassembly. In the unlikely event that happens again:
- Remove hose
- Release latch to lay hose fitting flat
- Remove two obvious screws
- Pry rear latches adjacent to hose fitting to release rear of top cover
- Pry side latches to release middle of top cover
- Pull rear of top cover away from base
- Disengage latches along front of beater bar
Those places, neatly marked for future reference, with the top cover against the floor:

Kenmore Progressive vacuum – carpet brush – disassembly latches

With the cover off, the beater bar lifts out and you can easily unwind the mess.
2017-02-09
Forester: TPMS FTW, Redux

Now I know the Forester’s TPMS icon blinks on 1000 feet from a cold start with 12 psi in the offending tire. I returned home and pulled this from a sipe in the left rear tire:

Road debris – blade fragment

It’s atop a 0.1 inch grid.

The flat side on the right rode tangent to the tire surface, recessed slightly below the tread, and pretty much invisible inside the sipe. Of course, the point punched through the tire’s steel belt and let the wind out, ever so slowly.

I initially thought it was a utility knife blade fragment, but under the microscope it looks more like a saw blade tooth. It’s obviously been kicking around on the road for quite a while; back in the day, they occasionally swept the roads, but that was then and this is now.

Makes me glad I didn’t buy four new tires after the last flat. I suppose installing two plugs in the same tire counts as a net loss, but they’re small, widely separated injuries and that’s how it’ll roll.

For the record: with 14 k miles on the tires, tread wear = 2/32 inch of the original 6/32 inch depth.

Those tires should last another 30 k miles at our current pace, although I expect more random debris will kill one stone cold dead before that.

2017-02-08
X10 TM751 RF Transciever: End of Life

X10 control from the two HR12A remotes got much worse over the last few months and eventually failed completely, which meant I had to actually walk over to the lights and click the switches. Not to be tolerated, sez I, so I would walk to the bedroom and poke the appropriate buttons on the wired controller (long since obsolete) by the bed. That worked perfectly, which eventually convinced me to dismantle the TM 751 transceiver.

It’s not good when soot plates the case:

X10 TM751 – Smoked case

I like how they capacitively coupled RF from the antenna for complete line-voltage isolation.

The PCB looked like it got rather hot over there on the left side:

X10 TM751 – Overheated PCB

A Zener diode on the component side of the PCB looked a bit toasty, so I decided this gadget had passed its best-used-by-date and dropped it in the electronics recycling box (after harvesting the antenna, just in case).

A new-in-box TM 751 from eBay arrived a few days ago and works just fine.

Done!

2017-01-29
Truth In Labeling: Bike Tube Division

The lumpy surface of the Michelin Pro-Tek Max tubes now in the back tire of our bikes can’t be patched, which means (being that type of guy) I must carry along a spare tube in addition to a handful of CO₂ cartridges. So, having cleaned out my tube stash, I ordered a pair from an Amazon supplier, not my usual bottom-dollar eBay suppliers, clearly described as fitting the Schwalbe Marathon Plus 700x35C tires.

The Amazon listing and the box label agreed, but (being that type of guy) I just had to extract the tube to see what I got:

Meetlocks tube size mismatch

Huh.

According to the seller, who speaks and writes English far better than I can handle Mandarin (or whatever):

Yes, you are right, you also didn’t bought wrong items for your tire. we marked the 700×28-32, just for our manufacture to difference from another big size from 700/35-45C, because if we marked the size 700×28-35C, sometimes , the worker will packing 700×35-45c into the packing, and let the tube can not used for the 700x35c customer..

Huh.

It turns out the tube has 35-38 embossed into the rubber, so it’s not obvious the tube would fit into the smaller 28-32 size tires as labeled. It all depends on what you trust: the mold, the tube’s stamp, the box label, or the advertising.

Next time around, an event I hope (but do not expect) lies far in the future, I’ll spend a bit more for what will undoubtedly be the same tube from the same factory, but from a vendor buying enough QC to ensure the workers know what they’re packing. Having all the labels match would be a definite bonus.

2017-01-28