I don't know if the Bishop Graphic sick-on tapes and pads are
still available.\ufffd If so would it be practical to take your scans
put some tracing paper on top then build up the image on the
tracing paper with the stick-on tapes and pads.\ufffd
Would be time consuming but give accurate multi pin parts.
Cheers,
Will
\ufffdThanks so much for all this!
\ufffd
Yes, I think this will be a very difficult project.\ufffd But I like challenges, even if I fail.\ufffd
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Unfortunately as far as I know there are no better copies of the artwork.\ufffd The mail-in offer for these plans was out only briefly in 1976 and so far only one person has come forward with originals, which is what these scans were based on.\ufffd Cleaning up the artwork will take a long time but I don\ufffdt think it\ufffds impossible \ufffd I\ufffdd just hoped for some faster method.
\ufffd
Recently I acquired an original set of plans for the 1974 Mark-8 mini-computer.\ufffd I have original boards and now these, but had originally planned in the absence of both to make clone boards from scanned copies of the plans online.\ufffd I was stunned to realize just how badly off the scans were when I compared the three.
\ufffd
Likewise on my TV Typewriter.\ufffd Although I had the foresight to print every pattern after scaling and check each individual IC, I neglected to consider the bus connectors that stack the four TVT boards together vertically.\ufffd I\ufffdve made it work but it\ufffds an awkward squeeze, because one of those connectors is skewed slightly to the left.\ufffd I have printed off several random sections of this artwork after scaling it correctly and so far tihngs fit perfectly.\ufffd I don\ufffdt have to worry about connecting other boards, so I can use the techniques I\ufffdve learned to get top and bottom perfectly aligned.\ufffd But yeah, the through plate situation is tricky.
\ufffd
I mean, I could just adopt the approach used by Mark-8 builders \ufffd even the original boards, although double-sided, were not through plate. You had to solder on both sides.\ufffd I could do that, although the original board in this case had IC sockets.\ufffd Not sure how you\ufffdd solder both sides of a socket.
\ufffd
One other thing I\ufffdm thinking about now.. this board is much larger than 8x11 \ufffd I\ufffdm guessing my only option re: toner transfer is to use two blue press n peel sheets per side?
\ufffd
Thanks for all your help and information!\ufffd It is greatly appreciated.
\ufffd
\ufffd
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 15, 2017 9:24 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Good techniques for cleaning up old artwork?\ufffd
\ufffd
Brad,
I looked at your artwork scans. WOW. Has anyone suggested that you might be a glutton for punishment?
I noticed that the first two scans are much cleaner than the others. If you have access to the pages that they were scanned from, you should re-scan with the lines square to the scanning direction. This will produce much cleaner results.
Before you invest too much time is trying to make clean artwork using the scans as a basis, make sure that the scanning process didn't distort the dimensions in one direction or the other. I have found small differences in the scaling between the x and y axes that make assembly of 40 pin ICs, or long connectors impossible.
These boards will be difficult to etch. The combination of large open spaces and very narrow traces may make it difficult to keep the traces from over etching.
To answer your question about plated through holes, they can be done, but it is a bit involved. There are a number of tutorials on making plated through holes on YouTube. Here are two of them:
Process 1:
https://www.youtube.com/watch?v=KTNuTv_IQp4
Process 2:
https://www.youtube.com/watch?v=s3GY-j4Gh0E
https://www.youtube.com/watch?v=9rME-XGCcCo
I have not tried either of these processes, but they do seem possible.\ufffd The difficulty I see with your boards is the sheer number of holes. The possibility that one or more of the holes, especially the small via holes, not getting plated through is very great. Finding an open would be very difficult, not to mention time consuming.
One thing to remember: The holes are drilled and plated before the board is etched. This means that the holes need to be protected during the etching process. It seems to me that the best process for doing this would be the photoresist process. The photomask used for resist exposure would need to have the drill holes omitted, so the resist will tent over the holes during etching. Drilling before photomasking has the benefit that it makes the mask easier to align. I would suggest that some extra pads with holes should be included on the masks to assist with alignment. These pads would include the drill holes. This also improves the probability that two sided boards would have proper alignment between sides.
Harvey
On 2/15/2017 6:04 PM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:
\ufffd
My TV Typewriter project is getting close to the finish line so I\ufffdm working on lining up a new project.
\ufffd
What I\ufffdd like to do next is a replica of the SOL terminal prototype that appeared in Popular Electronics in July of 1976.\ufffd I have the artwork for it here:
\ufffd
http://www.sol20.org/articles/img/PE_SOL.pdf
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As you can see, the quality of the scan is pretty lousy.\ufffd There\ufffds no other sources for this that I\ufffdve found.\ufffd I can clean it up manually with Photoshop or Illustrator (and in fact have started on the former) but that will take hours (months, probably).\ufffd I\ufffdm wondering if there\ufffds a better technique than endlessly using the rectangle tool to remake the traces and remote the \ufffdnoise\ufffd.
\ufffd
I expect there will be other challenges, being that this is a double sided board.\ufffd There *isn\ufffdt* a way for a home PCB maker to do thru-plate without third party help is there?\ufffd I don\ufffdt want to send this off to a board house because of the likely cost but also because that\ufffds not how a hobbyist would have done it back then.\ufffd Since this artwork was sent to those that wrote in for it, I\ufffdm assuming they just created it as a two sided board the usual way and then soldered in the connections between sides via ICs, jumper wire, etc.
\ufffd
I also don\ufffdt want to completely redraw the thing.\ufffd For me, that would lose the spiritual connection to the original artwork.\ufffd I\ufffdm trying to leave as much of it as original as possible.
\ufffd
Anyway, thoughts and suggestions here are most welcome.
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