Tracing a vintage PCB in KiCAD

[falter]

I've invested a bit of time trying to learn the ins and outs of KiCAD (it's the only software I'm even remotely familiar with for this task). I've been practicing on some Sphere boards as well as the Sol prototype PCB, trying to figure out which techniques work best for tracing. What I'm aiming for is very high fidelity to the layouts - keeping their 1970s 'handmade' styling intact. Upgrading to v7 with KiCAD was a huge help; it made bringing in an image file to trace a lot easier, and I've found a plugin that helps make curves. I set the grid to the smallest possible setting to allow fine adjustments to the traces.

Where I'm a bit lost is things like IC pads - KiCAD as a bunch in its library but they're modern looking - I want them to look like in the first attached image. At first I tried making shapes, but then I couldn't put a thru-hole in the middle to connect to the other side. I then tried doing it with tracks, and I can plant a via in the middle but I'm not sure what that comes out looking like on the other side, or how the board house would interpret it.

It's been suggested to me to just treat the artwork as art, and simply import the cleaned up images I have from the construction guide. My concern with this is how to line them up properly, since they will definitely not be perfect for that, and then again how to handle vias, etc. There are also other oddball shapes, some are easy enough to draw out but again, how to put vias in them.

I note Labomb was able to come up with an amazingly accurate reproduction of the Sol prototype board, but I'm not sure exactly how he traced things so faithfully or what software was used.

 

[jplr]

There was a plugin made for KiCad and used for a Kim-1 replica by Eduardo Casino, that replicates the "old" look.
Here is a copy if his readme of the Kim-1 replica, it has a lot of information:

# KIM-1 Replica

## Introduction

Welcome to the MOS KIM-1 reproduction project repository, where you will find what aims to be a faithful replica of the MOS KIM-1 computer, in particular a revision "D" PCB, based on photos and information gathered from various sources on the internet. With minimal modifications, later revisions should be easy to reproduce as well.

The KIM-1 was a single-board computer released in 1976 by MOS Technology, later acquired by Commodore, as a demonstrator of the capabilities of the recently released 6502 microprocessor.

## About

This recreation has been an excruciating process using entirely free software: Inkscape, Kicad and Freecad.

First, a high resolution image of a KIM-1 was used as a template in Inkscape. The image was resized to scale using the IC footprints as a reference. Then, the rest of the footprints were placed and the tracks were traced using bézier curves. I used a layer for each type graphic components (footprints, tracks, copper zones, typography, ...)

The logo was created from the MOS logo, adding the commodore name with the [Eurostile Extended 2 Bold font](https://fontsgeek.com/fonts/eurostile-extended-2-bold).

Component references where placed with the [Futura STD Bold font](https://fontsgeek.com/fonts/Futura-Std-Bold). The [Arial-like Aria font](https://fontsgeek.com/aria_1-font) was used for other typography.

The inkscape image was imported from Kicad to an user layer and used as a template for placing the footprints. Then, the image with the tracks was imported to the copper layer and converted to kicad tracks, so it was possible to check the pcb against the schematic.

The logo and the typography were converted to footprints using the svg2shenzhen plugin.

This is the end result:



WARNING: I have not yet sent the board to fabrication, so it is untested!

## Licensing

This is a personal project that I am sharing in case it is of interest to any retrocomputing enthusiast and all the information in this repository is provided "as is", without warranty of any kind.

[](http://creativecommons.org/licenses/by-nc/4.0/)

This work is licensed under a [Creative Commons Attribution-NonCommercial 4.0 International License](http://creativecommons.org/licenses/by-nc/4.0/).

EXCEPTION: The electrical schematic and all the associated symbols are licensed under a [Creative Commons Attribution 4.0 International License](https://creativecommons.org/licenses/by/4.0/).

See the LICENSE.md file for details.

## Acknowledgements

* Hans Otten and his [Retro Computing blog](http://retro.hansotten.nl/). Tons of information and high resolution pictures of various KIM-1
* Chuck Hutkins, for his [hi-res scans of an unpopulated Rev. D PCB](http://retro.hansotten.nl/6502-sbc/kim-1-manuals-and-software/kim-1-revisions/)
* Budi Prakosa "badgeek" for the [svg2shenzhen](https://github.com/badgeek/svg2shenzhen) plugin for Inkscape
* Ralf (User ralf02 from forum64.de) for info on actual dimensions of a KIM-1 and ideas from [his thread on a KIM-1 clone](https://www.forum64.de/index.php?thread/124855-instandsetzung-und-nachbau-eines-kim-1/).

 

[djg]

Where I'm a bit lost is things like IC pads - KiCAD as a bunch in its library but they're modern looking - I want them to look like in the first attached image.

KiCAD does oval pads or is there something more subtle I'm missing?

 

[falter]

Yes I just had to modify them to be the correct size for this board. I think I have it now.

Another question. Let's say I do this as a 2 layer board but then later want to add a middle layer, so I can make all the connections Proc Tech made with jumper wires, but hidden, is it easy to add a third layer in between, after the fact? I was trying to figure out how to add more layers.. it seems to want to add them in multiples of 2.

 

[Jove]

No pcb manufacturer does 3 layer boards, or at least not at a reasonable price. Use the extra layer as a ground plane and otherwise ignore it.

 

[VERAULT]

Call me crazy I would love to watch a video on you using kicad to copy boards. It can be abridged of course. I honestly hate those multi hour live stream repair videos where the youtube person chats with people. I mean I really hate them and dont like how so many do this.. But a real video shows some basic steps and your process on making board copies would actually be pretty interesting.

 

[falter]

Oh this is definitely going in a video. On my channel I started a series called 'Raising the Digital Dead'.. I want to resurrect old electronics projects from old magazines (not specifically computers). But being the megalomaniac I am I had to open the series with the Sol project. Which is probably not good since it's a big complex project and I tend to weave in and out of my projects which makes them take forever.

Anyway I've been recording with OBS the process. Just have to remember to stop recording.. the other say I realized it had been going for a couple days and I had a 30+gb capture.

I'm sort of figuring it out but am deathly afraid that I'm doing it wrong and am going to invest all these hours just for find out the board house can't use it or something. The hardest part is getting the two images, one for each side of the original artwork, that I imported for tracing purposes to line up. I adjusted them in photoshop to make sure all pads and vias lined up.. but for some reason when imported to Kicad it twists and stretches a bit and I can't line them up.

And then I'm not sure how to delete them once my work is done. Lot of learning!

 

[daver2]

An observation from other's work (not to detract from it in the slightest of course):

Entering the schematic into KiCAD will provided added checks that just a bare PCB cannot. For example, unconnected inputs to gates etc. These will be flagged by the Design Rule Checker (DRC). If they really should not be connected, you can add an 'X' to the input on the schematic and the DRC message will go away - but the author of the work has then made a conscious decision to NOT connect this input to 0V or VCC (via a resistor if necessary). These rules can identify 'original sin' issues with the historical boards that could lead to unreliability. You can then make an informed decision as to what to do with them...

1. Leave them as they are (e.g. unconnected) - but you now have a list of them. They could cause problems with the board when it is produced. In this case, your first option would be to tie the unused inputs with wire to ensure that this is not the root cause of your problems.

2. Make a 'better' PCB - but identify the changes you have made.

There is no right or wrong answer - just shades of grey...

Dave

 

[falter]

Here is how things are set up currently. I basically have an image of the original PCB artwork for the top in a user layer, the bottom, horizontally flipped, on the other. I did my best to align the two in Photoshop first so that they'd be easy to align here. I used the shape tool in KiCAD for the ground plane, and have created some vintage oval style DIP packages for the ICs that I'm placing.

I'm trusting that shapes appear to the board house as 'put copper here'.

One thing I'm not sure about.. there are some irregularly shaped bits which ordinarily I'd be inclined to use the shape tool on, except KiCAD doesn't seem to have a way to put a via in it as the artwork calls for.

And Dave - I would love to enter the schematic... it's a bit over my head but I might attempt it just to see what happens, before I get too invested. Of course, this SOL PCB design we already know is broken... so I'm not sure how things will pan out.

 

[furball1985]

going back years ago.
I used photoshop to trace out hard to see pcbs using settings for fill threshold or by hand with the pen tool. i would also change the colors so that everything would stand out next to each other and i could confirm it looked right.

then i place the photoshop file as a layer in illustrator and lay out the board with crisp Vector graphics in illustrator. with illustrator you could trace any shapes and recreate them,
then output the entire thing a few different ways depending on how you needed to bring it into another program, and you can setup layers and isolate different parts of the board your making
so that you can easily check if you made a mistake or the board is wrong and needs a fix.

From there i would flip/mirror the work area and create the PCB mask.
for a 2 sided board i would have alignment holes and make sure both sides lined up.

I would use the old method of High gloss laser paper and laser printer which would take up to 13x19 sheets.
i would take those and prep a piece of copper pcb nice and shiny, then using a clothes iron, align my sheets I would melt the Laser toner into the copper. then soak the pcb in the sink to remove the paper.
go back and inspect to make sure the toner transferred, fix with a sharpie pen as needed, then soak it in Etch.

time consuming but worked every time.

i used modern programs where you enter the schematic but then there are all kinds of rules that you add when the pcb is simulated and i could never get things to match automatically, then the auto arrange would dive me nuts.
and i would start locking components in place on the simulated board, hours and hours of my time when i know i could have done my method above and been done already.

 

[falter]

What I'd really like to do here is just match these in Photoshop, print them on a laser and iron to PCB, but I do not have a printer that prints larger than legal unfortunately.

 

[furball1985]

the difference will be the quality that ends up on the paper. illustrator vector art will print on paper with a very obvious crispness to the edges, photoshop regardless of resolution will print blurry.
when both are side by side on paper from the same printer you can see it night and day.

that is why the extra step is done. if you have a lot of close thin traces on the pcb then the transfer already difficult will be really messy with photoshop and require a lot of post clean up with a hobby knife to get the mask off where it should not be.

there are some cheap options for old laser Office printers that can do either 12x18 or close to 12x18 you can find a partially working 8150 office printer with a bad Paper selector super cheap, so long as the fuser power supply isn't blown, but even that is a known repair on these not too expensive.
another option is hit the staples and ask them if they can print laser on large stock you provide. then you can order the largest high gloss paper and run out a few masks that way.

 

[seat safety switch]

I'd also rather spend a few dozen hours in KiCad chasing traces and have the benefit of the DRC and "figure out for me where this net goes," than to do a bazillion drills for a photoresist board. You can always print it after if you so wish

That said, blowing it up really large and marking it up with a pen as you work on the recreation of the scan in KiCad to track your project/doubts/paranoia is a worthwhile endeavour; I work at least half on paper for anything complex.

 

[hideehoo]

Just throwing out Sprint Layout again given the positive experience I had with it recreating a Ferguson Big Board from some scans. No ERC/DRC though.

 

[1944GPW]

Could a prototype board be done by milling the PCB? David at Usagi Electric seems to put his mill to great use, churning out a lot of boards for his valve computer. He seems like an approachable guy, maybe he could give you some advice?

 

[shirsch]

Just throwing out Sprint Layout again given the positive experience I had with it recreating a Ferguson Big Board from some scans. No ERC/DRC though.

I just looked at Sprint. Appears to be useful and the current version does have DRC checking.

 

[furball1985]

Could a prototype board be done by milling the PCB? David at Usagi Electric seems to put his mill to great use, churning out a lot of boards for his valve computer. He seems like an approachable guy, maybe he could give you some advice?

yes you can, but there is a limit with the size of the tooling and how much deflection your cnc has. if you have 1/64" traces next to each other cnc isn't going to work, there is laser cutters, i have seen where you spray paint the Copper then use the laser to burn the paint off then go toss it in the etch, but at that point you might as well go back to the photo light exposure table with UV and a reactive coating then go etch it in solution.

and there is a 3d print option as there is conductive filament you switch to a .25mm nozzle and print the board up.

but in this case your trying to match to board from the 70s-80s and what it would look like from that time period.

in the magazines that offered masks it was transferred to a clear film and the copper was coated with a kind of mask that reacted with UV light, you would burn the pcbs in UV light and depending on if the coating was designed for pos or negative development would determine how your mask looked as either a pos or negative image. the UV would harden the coating on the unexposed areas. then wash away the coating that was not exposed and that gave your board.

it made sense in college campuses because they always had a photo lab you could access, it was basically the process for development of film from a camera. if there was a offset printing dept then you had access to a plate developer table where you setup your film and trapping to make offset plates for the presses. or home hobbyists would have a film developer setup.


homebrew

How to Etch a Two Layer PCB with UV-sensitive Copper Clad | ch00ftech Industries

ch00ftech.com

 

[Bruce Tomlin]

Yes I just had to modify them to be the correct size for this board. I think I have it now.

Another question. Let's say I do this as a 2 layer board but then later want to add a middle layer, so I can make all the connections Proc Tech made with jumper wires, but hidden, is it easy to add a third layer in between, after the fact? I was trying to figure out how to add more layers.. it seems to want to add them in multiples of 2.

That's because of how they're made, they make multiple 2-sided boards and laminate them together. Usually a 4-layer board uses one of the inner layers for ground.

Could a prototype board be done by milling the PCB? David at Usagi Electric seems to put his mill to great use, churning out a lot of boards for his valve computer. He seems like an approachable guy, maybe he could give you some advice?

Milling needs special consideration for the dimensions and spacing of traces. It's not for doing a 1:1 repro of an etched board. But it sure does look nice at the parameters he sets for those boards.

 

[falter]

Can I give a board house vintage PCB stock to use for the etching?