Tek Circuit Computer: Cursor Hairline Scraping

Engraving a PETG sheet with a diamond drag engraver on the Sherline and filling the scratch produces a good-looking hairline, but there’s a tradeoff between having the protective sheet pull the paint out of the scratch and having the crayon scuff the unprotected surface. This time around, I scribbled the crayon through the protective film, let it cure for a few days, then scraped the surface to level the paint and see what happens.

First, an unscraped cursor:

Tek CC - Cursor red lacquer - plain - overview
Tek CC – Cursor red lacquer – plain – overview

Peeling the transparent protective film:

Tek CC - Cursor red lacquer - plain - partial peel
Tek CC – Cursor red lacquer – plain – partial peel

The hairline is solidly filled:

Tek CC - Cursor red lacquer - plain - peeled
Tek CC – Cursor red lacquer – plain – peeled

Scribbling another cursor the same way, then scraping the protective film to flatten the shredded edges:

Tek CC - Cursor red lacquer - scraped - overview
Tek CC – Cursor red lacquer – scraped – overview

The hairline remains filled, but not as completely:

Tek CC - Cursor red lacquer - scraped - partial peel
Tek CC – Cursor red lacquer – scraped – partial peel

A closer look:

Tek CC - Cursor red lacquer - scraped - peeled
Tek CC – Cursor red lacquer – scraped – peeled

Scraping the crayon off the film removes a substantial amount of paint from the hairline, but, on the upside, the protective film does exactly what it says on the box and the PETG surface remains pristine.

Both hairlines are, at least eyeballometrically, Just Fine™ for their intended purpose.

Tek Circuit Computer: Water Test

So the question came up: “Exactly what happens when one of those things gets wet?”

Which obviously requires an experiment:

Laminated Tek CC vs Water - start
Laminated Tek CC vs Water – start

That’s the mis-cut top deck revealing why GRBL really needs four digits after the decimal point, but, other than that, it’s perfectly representative of the genre: heavy paper, good ink, nicely laminated in plastic.

Prediction: water should seep into the paper, dissolve the ink, maybe delaminate the plastic, and generally make a mess.

Which is exactly what happens:

Laminated Tek CC vs Water - finish
Laminated Tek CC vs Water – finish

User Advisory: your shiny new Homage Tektronix Circuit Computer is not waterproof, so don’t use it in the sauna!

Pickett 110-ES Circular Slide Rule Manual: Scanning Thereof

Having mostly finished futzing with the Homage Tektronix Circuit Computer, my Pickett 110-ES Circular Slide Rule once again came to mind:

Homage Tek CC vs Pickett 110ES colors
Homage Tek CC vs Pickett 110ES colors

Casual searching didn’t reveal an online copy of its manual, so here ya go:

After a cluestick whack, here’s a better-looking version made with ScanTailor, as installed from the normal Ubuntu repo:

There’s some backstory, of course …

I gimmicked a scanner fixture to align a pair of pages:

Pickett 110-ES Scanning Fixture
Pickett 110-ES Scanning Fixture

Yes, I destroyed the collectible value of my manual by removing two slightly rusted staples.

The black paper taped to the scanner lid prevents the type on the upper surface of the paper from producing dark blurs.

Set up XSane for batch scanning (one selection over each two-page spread), get a pipeline going (disassembly → face up → face down → reassembly), and eventually create 34 images named Scan-??.jpg. They’re in color, although it matters only for the rust stains around the staple holes, with the contrast stretched enough to make them mostly B&W.

Somehow, Pickett printed / cut half the sheets slightly off-kilter, so I rotated them -1° rotation to re-align the text. To simplify plucking the rotated pages out of the image, composite the spread atop a blank white background:

for i in $(seq -w 3 2 33) ; do composite -compose atop Scan-$i.jpg -size 2200x1400 -geometry +100+100 canvas:white -rotate -1 Comp-$i.jpg ; done

Rather than thinking too hard, do exactly the same thing to the other pages without rotation:

for i in $(seq -w 2 2 34) ; do composite -compose atop Scan-$i.jpg -size 2200x1400 -geometry +100+100 canvas:white -rotate 0 Comp-$i.jpg ; done

Each scanned image has two pages, so crop it into two files with names corresponding to the actual page numbers:

for i in $(seq 2 2 34) ; do convert -crop 960x1240+1050+110 Comp-$i.jpg Crop-$(( $i - 1 )).jpg ; done
for i in $(seq 3 2 34) ; do convert -crop 960x1240+130+110 Comp-$i.jpg Crop-$(( $i - 1 )).jpg ; done
for i in $(seq 3 2 33) ; do convert -crop 960x1240+1050+110 Comp-$i.jpg Crop-$(( 66 - $i )).jpg ; done
for i in $(seq 2 2 32) ; do convert -crop 960x1240+110+110 Comp-$i.jpg Crop-$(( 66 - $i )).jpg ; done

Fix the single-digit pages to simplify globbing later on:

rename 's/-/-0/' Crop-[1-9].jpg

A bit of tedious fixup for some truly misaligned sheets produced images with slightly different sizes, so composite all of them onto slightly larger backgrounds to avoid screwing up the PDF conversion:

mkdir Final
for f in Crop* ; do composite -compose atop $f -size 1000x1300 -geometry +10+10 canvas:white -Final/$f ; done

Then jam them into a PDF for convenience:

cd Final
convert Crop-C[12].jpg Crop-[0-6]*.jpg Crop-C[34].jpg "Pickett 110-ES Circular Slide Rule Manual.pdf"

You can print it six-up to a sheet to produce text just about the same size as the original manual. If you omit (blank) cover pages 2, 67, and 68, the whole thing fits neatly on 11 sheets of paper.

Someone with better facilities and more attention to detail can surely produce a better-looking result, but this will be better than nothing.

Tek Circuit Computer: Cursor Hairline Filling

Some cleanup and a fresh layer of double-sided tape gives the cursor milling fixture plenty of adhesion:

Tek CC - Cursor blank on fixture
Tek CC – Cursor blank on fixture

This time, I diamond-scribed three PETG cursors through the transparent protective film, with two / four / six passes:

Tek CC - Cursor hairline filling
Tek CC – Cursor hairline filling

It’s not a Purple Crayon, but it suffices for my simple needs.

Scribbling a (soft!) lacquer crayon over transparent plastic still scuffs the pristine surface around the engraved line, so I tried scribbling the six-pass cursor before peeling the film, as shown above. Unfortunately, the film shreds left around the line either prevent a clean fill or pull the paint out of the ditch as the film peels back:

Tek CC - Cursor lacquer fill
Tek CC – Cursor lacquer fill

Peeling the film and scribbling ever-so-gently left a more complete line, but, if you look very closely (perhaps opening the image in a new tab for more dots), you can see the scuffs left by the scribbles on either side of the line:

Tek CC - Cursor 2 4 6 scribes
Tek CC – Cursor 2 4 6 scribes

When seen from the other side against laminated decks, though, the scuffs pretty much vanish:

Tek CC - Classic Tek Logo vectorized - red hairline
Tek CC – Classic Tek Logo vectorized – red hairline

The red hairline isn’t historically accurate, but I like the way it looks.

Give me some (heavyweight matte) paper and a (lacquer) crayon, put me in a basement (shop), and I’ll be happy for days

Tek Circuit Computer: Formula Layout

Although Inkscape can lay out simple text in many intricate ways, there seems no way to typeset mathematical equations, even the simple ones involved in the Tektronix Circuit Computer.

So I entered the equations in LibreOffice’s math editor, zoomed in on each equation to the maximum 600%, whacked the little-used PrntScr key, cropped out everything except the equation, and saved it as a PNG file:

Tek CC - Bottom Deck Back - FR formula
Tek CC – Bottom Deck Back – FR formula

Import the PNG files into Inkscape, fiddle with the line spacing to get enough room, and jockey everything into position:

Tek CC - Bottom Deck Back - formula detail
Tek CC – Bottom Deck Back – formula detail

Bit of a kludge, but it looks Good Enough™.

Homage Tektronix Circuit Computer: Minimally Viable Product, Pickett Variation

This one came out just about perfect:

Tek Circuit Computer - MVP - Pickett Edition - front
Tek Circuit Computer – MVP – Pickett Edition – front

The yellow decks may not be authentic, but they definitely look nice; think of it as an homage to Pickett’s Eye-Saver Yellow slipsticks.

The rear has my how-to-operate hints:

Tek Circuit Computer - MVP - Pickett Edition - back
Tek Circuit Computer – MVP – Pickett Edition – back

Laser-printing on “inkjet” paper worked fine, although this isn’t fancy Gloss-coated Brochure paper, and the text looks like it should.

The cursor sports a two-pass hairline scribed at 330 g and filled with Lacquer-Stick paint:

Tek CC - Milled PETG cursor - Lacquer-Stik hairline
Tek CC – Milled PETG cursor – Lacquer-Stik hairline

This time, I had the clear film on top!

Although the picture doesn’t do it justice, the scales are in blue ink, which looks better against the yellow background. I suppose I could do custom colors:

Pilot V5RT cartridge - ink levels
Pilot V5RT cartridge – ink levels

The line width has decreased as the ink level drops: 0.3 mm on yellow card stock and 0.2 mm on glossy white brochure paper. I don’t know if they’re supposed to work like that, but, for this application, narrower lines are definitely better.

Tek Circuit Computer: Paper Matters, Redux

The back of a Tektronix Circuit Computer’s bottom deck carries instructions and information:

Tektronix Circuit Computer - rear
Tektronix Circuit Computer – rear

A separate instruction manual told you how to use the thing, under the reasonable assumption you’d be intimately familiar with slide rules.

In this day and age, the back should carry how-to-use instructions, so I summarized the manual into half a dozen lists:

Tek CC - instructions - first pass
Tek CC – instructions – first pass

Which looked fine & dandy & ready to print, thereby exposing various typos / inconsistencies / misalignments:

Tek CC - test print - HP Brochure vs ordinary copy paper
Tek CC – test print – HP Brochure vs ordinary copy paper

Whereupon I (re)discovered just how much paper matters.

The HP Brochure Glossy inkjet paper on the left produces wonderful results with a 0.5 mm Pilot V5RT ball point pen and has coating on both sides. It’s intended for handouts, brochures, and suchlike; the Pilot pens produce identical results on either side.

The same text, printed on plain old 22 pound “multipurpose” paper on the right, looks much better and makes the HP paper looks like something done with crayon on paper towel.

I could try a font with finer strokes, but … ick.

It’s unclear whether Brochure Matte paper would make any difference, nor whether running coated “inkjet” paper through a laser printer would have an … infelicitous … outcome.

Past experience shows the unsteady ziggurat of Linux printing doesn’t respond well to tweakage: when the default settings don’t work, there’s no easy / predictable way to change any particular setting.

For future reference, print the instruction on what will become the back of the bottom deck, mark the center point, tape it to the CNC 3018 platform, touch off XY = 0 at the center, and draw the front scales: everything lines up perfectly without extra fuss & bother.