Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
A power failure apparently pushed the ancient RCA alarm clock over the edge into a mode where it ignored its pushbuttons and displayed a time based on a hitherto unknown exoplanet. Popping the case revealed it’s been simmering in its own juices for quite a while:
RCA Alarm Clock – PCB overheat
There’s nothing obviously scorched on the underside of the PCB, although a large SMD resistor might be the source of the problem.
Having been around this block a few times, I unsoldered that big electrolytic cap with its guts protruding from the overwrap:
RCA Alarm Clock – failed cap value
Nope, that’s not really an electrolytic cap any more.
Lacking a 2200 µF cap of suitable voltage rating, but knowing cap tolerances allow for considerable windage, this worked out well enough:
RCA Alarm Clock – replacement caps
Two smaller caps measuring on the low side of OK now reside in the e-waste box.
The white diffuser over the last digit improves it in ways I do not profess to understand, but am pleased to implement:
RCA Alarm Clock – in place
It’s held in place by two strips of LSE tape to see how it reacts to prolonged shear force, no matter how gentle.
Combining a new mailbox with a post and an old mailbox I had on hand, upcycling some scrap wood, then sticking on a few digits and a seasonal decoration found on a walk, should shake loose the mail currently stuck in the USPS delivery system:
Mailboxes – south view
That’s an Extra Large mailbox, suitable for most packages arriving by USPS, and dwarfing the ordinary mailbox on the north side:
The boxes sit on slabs harvested from an old door and screwed to two layers of Chinese plywood from the laser cutter’s shipping crate, all unpainted / untreated interior-grade (at best) wood cut with a circular saw. My assumption is they’ll last long enough for the purpose and, not having formed a deep emotional bond with them, I won’t feel too bad when the assembly gets pulverized.
The whole affair sports a rakish tilt toward the street, in the hope of encouraging rainwater to run off, rather than soak in, but I fully expect the untreated plywood to act as a sponge and delaminate / curl / splay in a spectacular & amusing fashion.
The pale rectangle across the vertical post is a (laser cut!) Chinese plywood plate intended to hold the crossbar together. The vertical and horizontal posts meet in a simple cross lap joint that surely wasn’t intended to support nearly so much weight: reinforcement seems appropriate.
Mary’s PT requires a Shoulder Pulley, so I got one that seemed better constructed than the cheapest Amazon crap. In particular, this view suggested the pulley ran on a bearing:
Slim Panda Shoulder Pulley – detail view
Which turned out to be the case, but, also as expected, the whole thing required a bit of finishing before being put in service.
It’s intended to hang from a strap trapped between an interior door and its frame. The strap was intended to attach to the block (a.k.a. “Thickened base”) through a breathtakingly awkward pair of low-end carabiners:
Slim Panda Shoulder Pulley – carabiners
Which I immediately replaced with a simple, silent, sufficiently strong black nylon cable tie:
Shoulder PT Pulley – block hardware
Rather than let the metal block clunk against the door, it now sports a pair of cork-surfaced bumper plates:
Shoulder PT Pulley – side plates installed
A doodle of the block dimensions:
Shoulder Pulley – dimension doodle
Which turned into a simple LightBurn layout:
Shoulder PT Pulley Side Plates – LB layout
The blue construction lines represent the actual block & pulley, with the red cut lines offset 2 mm to the outside to ensure the metal stays within the bumpers. It’s possible to pick the block up and whack the pulley against the door, so don’t do that.
Cut out two pieces of 3 mm MDF, two pieces from a cork coaster (covered with blue tape and cut with the paper backing up), peel-n-stick the cork to the MDF, put double-sided foam tape on the block, peel-n-stick the bumpers, then hang on the attic door.
Getting comfy required a bank shot off the familiar chord equation to find the radius of a much larger circle producing the proper depth between the known width. The recess then comes from subtracting a hotdog from a lozenge exactly filling the wood pocket.
Ironing Weight Finger Grip – recess chord
A pair of grips takes just under two hours to print while requiring no attention, which I vastly prefer to tending the Sherline.
The wood pocket is 7 mm deep and the grips stand 6.5 mm tall, leaving just enough room for three blobs of acrylic adhesive to hold them together. After squishing the grips into their pockets, a pair of right angles aligned everything while the adhesive cured:
Ironing weight – grip adhesive curing
Mary asked for a longer weight for a place mat project, with a slightly narrower block to compensate for the additional length:
Ironing weight – seam ironing B
The grip and pocket were the same size, so it was just a matter of tweaking the block size and cutting more wood.
All in all, a quick project with satisfying results!
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The Smell of Molten Projects in the Morning 
