On Thu, 31 Mar 2016 21:54:50 -0700, you wrote:
>Sorry, what I meant by print the image in reverse is I assume I need to
>'mirror it'. Unless I'm misunderstanding the process, if I printed it as is
>on my glossy paper and ironed it to the PCB copper, I'd end up with an image
>that was backwards.
>
As was said, most PC boards are designed today looking from the top
through the board.
With the photoetch process, you just turned the board over to make the
text come out right, and typical designs were done on the bottom of
the board. The process ∗does∗ reverse the image, since from the
board's perspective you're flipping the image by turning it over.
Photoetch, no. Toner transfer, yes.
In eagle, the bottom layer is printed (and is designed mirrored, you
design the bottom layer through the board). So mirroring the bottom
layer is not needed, it's already done that way. Top? no, it must be
mirrored then printed, then it will come out correctly.
That's one good reason to always put text on a board, you can
immediately tell if it's going to be oriented correctly. In toner
transfer, ∗all∗ text (when you look at the printed transfer) should be
reversed.
Harvey
>
>
>From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
>Sent: Thursday, March 31, 2016 10:54 AM
>To: Homebrew_PCBs@yahoogroups.com
>Subject: Re: [Homebrew_PCBs] Got some single side boards
>
>
>
>
>
>On 31 Mar 2016 10:28:53 -0700, you wrote:
>
>>Picked up a bunch of these on ebay. Thought before I spend $400 I might as
>well see what I get with these and do some trial runs.
>>
>>
>http://www.ebay.com/itm/361162323034?_trksid=p2057872.m2749.l2649&ssPageName
>=STRK%3AMEBIDX%3AIT
>http://www.ebay.com/itm/361162323034?_trksid=p2057872.m2749.l2649&ssPageName
>=STRK%3AMEBIDX%3AIT
>>
>> I have a couple questions. I want to use, if possible, the original
>artwork provided to builders in 1973. Here is a sample of the mainframe
>artwork that I posted before:
>>
>> http://www.swtpc.com/mholley/TV_Typewriter/page_18.pdf
>http://www.swtpc.com/mholley/TV_Typewriter/page_18.pdf
>>
>> This is literally all I have to work with, since an original copy of the
>artwork is impossible to get now. So questions:
>>
>> Is it dark enough to be usable?
>
>I wouldn't be happy with it, no.
>
>> If not, what would be the best way to get it darker without altering it
>too much? I tried just 'paint bucketing' black onto it in Photoshop but it
>seeks out the less visible grey tones and 'thickens' the traces, and
>sometimes obliterates the drill holes.
>
>Change the color palette to monochrome, and then use a very fine brush
>to cover the holes, that's one way.
>
>> I'm assuming using the toner transfer method I need to print the image in
>reverse?
>
>No, the dark area is the toner which is transferred directly. These
>are fine.
>
>>I assume this image was intended to be used with the presensitized boards,
>thus it would be printed on clear overhead film and laid on top for
>exposure.
>
>Nope, not at all.
>
>Taken down to a photo/graphics shot and converted into a negative on
>kodalith film, then printed on KPR sensitized boards.
>
>OR
>
>Same process and use a positive acting system, where you coat the
>board completely with resist, print the positive pattern, develop it,
>then tin plate the board, remove the resist, then use ammonium
>persulfate or something that leaves tin alone and eats copper.
>
>So depends on what you wanted.
>
>> What would be the best way to get it to print at the correct scale. On
>other artwork I've seen actual scales (or ruler edges) displayed. For some
>reason that is not done here. I guess these would have been printed on
>standard 8.5x11 pages or something as life size. But because these were
>scanned from pages of a magazine it's not quite exact (I printed and
>compared to my ICs). I guess I could just scale it up a percent or so at a
>time, but I'm thinking there must be a more scientific way.
>
>Take an IC on the board and generate from it a measurement, or use the
>board edges as a scale. Then scale it up to the desired size from
>that.
>
>> Anything else to consider?
>
>It looks as if the paper when scanned was not completely flat, so that
>can be a small problem. If you could find a back issue of the
>magazine and then scan from that, it would be a lot better.
>
>Harvey
>
>>
>> Thanks guys!!
>>
>>
>
>