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.

Author: Ed

  • HP 7475A Plotter: Ceramic Pen Tip Wear

    An upcoming show-n-tell prompted me to make sure the HP 7475A plotter still worked and verify the pen stash. One of the ceramic pens expired during the first test plot and a refill didn’t improve its disposition, so I pulled a new-old-stock pen from its wrapper.

    As expected, the defunct pen’s ink supply core had worn down to the surrounding ceramic nib:

    HP 7475A Ceramic-tip pen - worn core
    HP 7475A Ceramic-tip pen – worn core

    The new pen looks like it has a brush sticking out:

    HP 7475A Ceramic-tip pen - fresh core
    HP 7475A Ceramic-tip pen – fresh core

    The new pen’s core looks slightly larger and, in fact, it’s labeled as 0.4 mm rather than 0.3 mm. The new-old-stock pen stash includes a few 0.2 mm ceramic pens; I should think of something requiring hairline detail.

    It passed the manual scribble test and promptly ran out of ink during its first plot. I injected some blue ink and it’s now plotting happily for the first time in its life.

  • Homage Tektronix Circuit Computer: Colored Scales

    Although the original Tektronix Circuit Computer had relentlessly monochrome scales, a dash of color added a festive holiday look:

    Tek CC - Pilot V5 - color test overview
    Tek CC – Pilot V5 – color test overview

    Well, OK, that’s excessive.

    The intent was to see how the pens behaved, with an eye toward accenting general-purpose circular slide rule scales with a few colored characters.

    The green pen shows how I built the arrows by drawing a line through vertical arrow characters:

    Tek CC - Pilot V5 - plain paper - letters
    Tek CC – Pilot V5 – plain paper – letters

    I like blue ink entirely too much, having used a blue pen as my daily writer for most of my adult life:

    Tek CC - Pilot V5 - plain paper - red blue
    Tek CC – Pilot V5 – plain paper – red blue

    Red ink for “backwards” scales and suchlike would work well, even if it’s too vivid for the tick marks:

    Tek CC - Pilot V5 - plain paper - red green
    Tek CC – Pilot V5 – plain paper – red green

    Those are all on unlaminated plain paper, with plenty of room for improvement.

    Seeing as how I’d be doing all the “tool changes” manually, optimizing the plotting sequence would be mandatory: one pen change per color per deck!

  • CNC 3018XL: Pen Variations

    Cheap 1 mm pens produce scratchy lines:

    CNC 3018 - Cheap pen - plain paper
    CNC 3018 – Cheap pen – plain paper

    More expensive 0.5 mm Pilot Precise V5RT pens produce well-filled lines:

    CNC 3018 - Pilot V5RT - plain paper
    CNC 3018 – Pilot V5RT – plain paper

    Both of those are on plain paper. Better paper would surely improve the results, while moving the cheap pen further into sow’s ear territory.

    For reference, the cheap pens use a collet holder:

    CNC3018 - Collet pen holder - assembled
    CNC3018 – Collet pen holder – assembled

    The Pilot V5RT pens use a custom holder:

    Pilot V5RT holder - installed
    Pilot V5RT holder – installed

    A 3D printer really simplifies making things!

  • Homage Tektronix Circuit Computer: Eyelet Pivot

    Although a sex bolt works as a central pivot, even the shortest one available in a cheap assortment is too long for three paper decks and an acrylic cursor:

    Tek CC - radial text example
    Tek CC – radial text example

    An eyelet / grommet intended for leather crafting works better:

    Tek CC - eyelet pivot - front
    Tek CC – eyelet pivot – front

    That’s the front side, with the stylin’ rounded head, in “gunmetal” gray. The shank is 5 mm ID (the advertised size), 5.5 mm (-ish) OD, 4 mm long beyond the 10 mm OD head. All dimensions vary unpredictably between sellers, so expect nothing in particular and you won’t be disappointed.

    The back side gets the washer:

    Tek CC - eyelet pivot - rear
    Tek CC – eyelet pivot – rear

    The entire stack is 1.7 mm tall: three 0.4 mm laminated decks and the 0.5 mm polypropylene cursor. The 4 mm shank length seems excessive, but works out well in practice, even if I need more practice at smoothly swaging shank over washer. It’s sufficiently good looking in person.

    Note: the washer goes on convex side outward!

    The set includes a hole punch suitable for leather work and slightly too small for paper, plus the swaging punch and die required for the washer.

  • Kenmore 158 Sewing Machine: Hardware Deglaring

    The matte mailing labels on the Kenmore 158’s hand hole cover plate did such a good job reducing the glare from the additional LEDs as to make the shiny hardware around the needle seem overly bright. I suggested gentle sandblasting might improve the situation without changing any surfaces in contact with the fabric.

    I was given a spare presser foot to demonstrate my case:

    Kenmore 158 Presser Foot - original - front
    Kenmore 158 Presser Foot – original – front

    The overhead light in the shop produces glare from the nice, shiny steel surfaces similar to what Mary sees from the sewing machine.

    A few minutes applying 220 grit blast media with Tiny Sandblaster™ definitely changed its appearance:

    Kenmore 158 Presser Foot - sandblasted - front
    Kenmore 158 Presser Foot – sandblasted – front

    In person, the finish is neutral gray overall, with those odd brown areas appearing only in photographs, perhaps due to the various lights in the shop. The slight texture variations seem to correspond to minor differences in the plating (?) over the steel surface. It definitely cuts down the glare:

    Kenmore 158 Presser Foot - sandblasted vs original
    Kenmore 158 Presser Foot – sandblasted vs original

    The needle clamp and screw across the top of that picture travel up and down, so we decided to deglare them along with the “good” foot:

    Kenmore 158 - foot with needle clamp - original
    Kenmore 158 – foot with needle clamp – original

    Another Tiny Sandblaster™ session knocked back their shine:

    Kenmore 158 - foot with needle clamp - sandblasted
    Kenmore 158 – foot with needle clamp – sandblasted

    Those parts came out slightly less matte, perhaps due to reduced pressure in the propellant can. Seeing as how I’ve had the sandblaster for a couple of decades, I figured it’s time to use the propellant but, as expected, the in-can valve doesn’t re-seal properly, so I’ll be using compressed air the next time around.

    After rinsing and blowing and rinsing and blowing the grit out of the threads, everything went back together as expected:

    Kenmore 158 - sandblasted hardware installed
    Kenmore 158 – sandblasted hardware installed

    I’m not doing either of the plates until we have more experience with the matte hardware, but it looks pretty good to me.

  • Scrap EEPROMs

    A quartet of defunct 64 KB EEPROMs (*) emerged from a box of microscope doodads, so I stuck ’em under the stereo zoom scope for final pictures.

    The oldest one, an MCM68764, came from Motorola with a 8313 date code. The next three, all TMS2764JL-25, came from TI with date codes in 84 and 85, so they have slightly different layouts.

    MCM68764C EPROM
    MCM68764C EPROM
    TMS2764JL-25 A EPROM
    TMS2764JL-25 A EPROM

    This one is rotated 90° counterclockwise:

    TMS2764JL-25 B EPROM
    TMS2764JL-25 B EPROM
    TMS2764JL-25 C EPROM
    TMS2764JL-25 C EPROM

    The hideous compression artifacts come from the original Pixel 3a images, because they’re (digitally) zoomed in all the way, plus bonus optical distortion from the quartz windows. The chips definitely look better in person, although the (optical) magnification isn’t nearly enough to show the tiniest details.

    (*) Uh, they’re just EPROMs. It’s been so long since I’ve typed it that the extra “E” just stuttered right out. That’s my story and I’m sticking with it … at least I got the image names right!

  • Car vs. Pole: That Ain’t Gonna Buff Right Out

    Spotted at the corner gas station, where they collect wrecks before harvesting their organs:

    Car vs Pole
    Car vs Pole

    As far as we can tell, the car clipped the pole off at the base, whereupon it smashed down across the roof, leaving the trunk unscathed. The lack of blood on the airbag suggests the driver lived to tell the tale, although we’ll never know the rest of the story.

    A collection of random stuff tossed on the back seat included a license plate bent into a surprisingly gentle curve.

    Obligatory: And Sudden Death reference.