It was a simple piece of cardboard with 3 wheels inside of it, dial in the colors and it told you the values of resistors, capacitors, and on the backside 2 scales of inductors! (catalog number 271-1210)
While no replacement for proper education on the subject, it proved itself more than useful, so useful I still own the darn thing to this day 20 + years later, and even mention it in one of my Instructables as "the best darn piece of cardboard they don't make anymore".
The problem with it is, when radio shack changed from Archer brand stuff in brown packages to R (circle) stuff in blue and white packages, and eventually dwindled their electronic supply down to a couple of cabinets from 3 walls of the stuff, this handy device disappeared.
Without getting into too much RS / Tandy / Archer history, I would guess it had not been produced since the mid 1990's ... and thats a shame.
I have been meaning to make my own similar version of the card ever since I started Instructables, but ironically, I was going nuts trying to figure out a cardboard project for the "Gorilla Glue Cardboard Contest"...
Then one night, planning out how to shove a Cmoy amp into a 9volt battery, I was using this thing and all of a sudden all the DUH's came into place!
Welcome to my 6th Instructable.
Step 1: Tools and Materials
Computer (which if your viewing this I have to assume you have access to at least one)
Color printer, one that you can feed the paper from the back in a direct line to the print heads and out again (I used my wifes horrid 5+ year old HP all in one inkjet), even if you have a printer with a 2 stroke weed eater motor attached, curling the cardboard around the typical paper feed rollers will ruin it
Ruler / Straight edge
Xacto / Hobby / Scalpel / Matt knife with a fresh sharp blade
Black felt tip marker (sharpie is what I used)
Thin cardboard, mine was cut out of a thick presentation folder / box, but the same thickness is often found in packs of plain underwear type T-Shirts
1 inch long "paper fasteners", thats the best name I can seem to find for them, they are a thumb tack sized doo-dad with 1 inch long thin metal strips on one side, put them in a hole and bend the strips over to hold paper. They are really common, I found mine at K-mart, in a pack o 100 for $1.29, but anyplace you can find basic office supplies should have them. Just for reference heres a link to some more fancy ones on staples.com
Step 2: Design of the Card (part 1)
The original radio shack card shows color codes for resistors, capacitors, and inductors, but to be totally honest, I have never used the inductor side, and rarely have I ran across color coded capacitors (in some vintage radio equipment maybe), so I choose to not bother replicating those, My card will do resistance only.
Also the radio shack card, in accordance with standard resistor color codes shows gold (/10) and silver (/100) on the 3rd band, again something thats not really likely to come up in hobby electronics, so due to part lazyness and part "how am I going to print metallic colors on a inkjet" those 2 are not included in the multiplier section.
The card can show values from 10 ohms to 99 meg-ohms with no confusion , and that should be just fine for most applications, heck the Radio Shack card only does 99 meg- ohms ...
Now on to the design but!
IF you have no interest in how I actually made the graphics for the card, and just wish to print out an image and assemble it please skip ahead to step 7
Step 3: Design of the Card (part 2)
The first thing to do is get some basic measurements of the original, which is 4 inches long * 2 inches tall, and contains 3 2 inch diameter wheels.
Using those dimensions its time to hit the computer and fire up Inkscape (or Adobe Illustrator, or Corel draw or any other vector type drawing program), and lay out some guides.
Next, off to the side I want to lay out some more guides for the wheels, basicly making a 2 inch * 2 inch square, also on the part used for the wheels I marked the centers of the X and Y axis, and on the X centerline I added 2 more guides on either side about 1/8th inch from the centerline.
I then drew a 2 inch circle using the guides outlined only, copied and pasted it and shrunk it down to about 1.75 inches, in order to evenly divide the circle into 10 even sections I drew 2 pentagons, and flipped one upside down and scaled them so that the point of the pentagons were touching the inside circle.
I then drew a 1/4 inch solid (with no outline) circle, and placed it in between my center marks on the inside of the inside circle at the 12 o clock position, next I placed a 0 (zero) on the outside of the inner circle at the 6 o clock position.
Step 4: Design of the Card (part 3)
Next I selected the black dot, and its zero and the outer circle and rotated the whole thing clockwise to the next point on the pentagons.
I then copied and pasted the black dot and zero thats now on the side of the drawing back into the center position on the circles, changed to brown and its value to 1.
keep doing this until you have all the colors and values all the way around the circle.
black = 0
brown = 1
red = 2
orange = 3
yellow = 4
green = 5
blue = 6
purple = 7
gray = 8
white = 9
Finally put a 1/8th inch black dot in the center of the wheel
Select everything you just did, group it together and move both out of the way for now.
Step 5: Design of the Card (part 4)
This is fairly easy to eyeball using the center point guides so thats what I did, the process is the same as before, place color, and value, then rotate and keep going until your done.
The colors and values on this wheel need to be
black = .0
brown = 0
red = 00
orange = 000
yellow = 0,000
green = 00,000
blue = 000,000
And don't forget to mark the center of the wheel with a black dot group everything on this wheel together and move off to the side
Step 6: Design of the Card (part 4)
Next draw a circle over the color circle at the 12 o clock position on the wheel, and a box around the number at the 6 o clock position, its now a good idea to rotate the circle to make sure all the numbers and color dots line up with what will be our windows in the final product.
Once we have everything nice and pretty, select everything you were just working on, copy it and paste it, position the copy where the outside of the second wheel is just to the left of the center dot on the first wheel also add another dot on top of the center dot of that circle to mark the hole on the card.
The 3rd wheel (the one with only 8 segments, or the second one we had to make) needs to be just to the left of the center dot of the second wheel, similar to the first wheel we will need to make a new box for the larger values, and rotate the whole thing to make sure it all lines up with the "windows", and add a dot on top of the center dot to mark the 3rd center hole of the card.
You will find that the third wheel sticks out of the side of the card, so what happened? When you use outlined shapes in most programs half of the outline is on the inside of the shape, the other half is on the outside, so our wheels are like 2.1 inches in diameter and our boxes are like 3.9 if your going by the outlines.
Don't worry were not precision machining something that our life depends on, just expand the side of the card a little bit, and since we will be cutting this all out by hand a little wiggle room is nice to have.
I then selected the whole lot, copied and pasted it in some open space flipped it horizontally and put it below for the backside, then deleted everything except the 3 center dots so we know where to cut on the back too.
Finally I moved the wheels back out of the card onto some open space, you can now see the 6 windows and the 6 hole markers we need to construct the card, along with the wheels in some free space, almost ready to print.
Step 7: Design of the Card (part 5)
Hopefully at this point in between my screen shots and loose instructions you should be able to construct this entire thing totally from scratch. BUT if you just want to change the graphics to your school, business, lab or whatever you should grab one of these files so you can just paint it
The gimp (and many other programs) can read svg files with no problem, but if your paint package does not, I have also included a png file that all image editors will open
For my card I choose to go with an Instructables.com design, featuring the site logo, the robot and color layout, and that is also included in the zip file
So download and get ready to print!
Step 8: Printer's, Man I Hate Printers
your printer will most likely differ but something along those lines is what we need, a way to feed paper from the back so this heavy cardboard does not have to go around the rollers.
On my particular piece of "magic" its not really designed to do this, so in order to get it to work I had to have paper in the front tray or it would trigger a jam condition.
Then I had to kinda push the cardboard in, then it would spit it out 4 or 5 times, and Finally print on it.
It took me about 15 min to get it to print the first time, but it started going at an angle at the last moment and skewed the card
The second time it did not take as long, but then my wife said, "you know the text on the back is backwards" and sure enough it was
SO about an hour of listening to this thing clunk about, clearing its software of paper jams, running the cardboard tru the dumb thing 4 or 5 times each print and really cheesing off the wife, (cause it was sitting about a foot from her head while all this was going on) I finally got the thing to print the card straight and proper on my last piece of scrap cardboard.
Depending on your printer and your penitence maybe your luck will be better, but In the end it DID do it and saved itself from me going "Office Space" on it
Worst case and you cannot print directly on the cardboard, you can always just print it out on paper and then glue the paper to the cardboard (but I was committed to the idea)
Step 9: Print It
you do not want any scaling rotation or anything, just plain and simple print
for you windows users out there you can use the picture and fax viwer included in windows and the print wizard thats in there
set your printer to its best quality, get the cardboard ready and let it go
Step 10: Cut It Out
Next using your knife cut out the centers of the 2 wheels, and the 6 black dots on the card.
Then cut out the "windows" in the cards, when it came to the 3 circular windows that the colors will show tru I kinda cheated and use a single hole, hole punch.
Go slow and take your time, make multiple passes with the knife to avoid slipping.
After cutting everything out I went around the edges with a black felt tip pin, to color the white edges but to also cover up where the bad printer + antialasing did not leave the outlines good and dark.
Step 11: Assemble
bend upwards in a 90 degree angle, then remove the ruler, continue bending the card until both halves meet.
Next get your first 10 segment wheel and line it up inside of the card where the center hole of the wheel lines up with the leftmost hole in the card, and run a paper fastener through it, repeat for the second 10 segment wheel for the middle hole, and the 8 segment wheel on the rightmost hole.
Once all the wheels and fasteners are in place use your wire cutters to trim the ends of the fasteners down to about 1/4 inch long, then bend them down.
Make sure they are fairly tight, but not so tight that the wheels will not move, and enjoy!