Abd ul-Rahman Lomax wrote: > At 06:00 AM 2/8/2002 -0500, Darryl Newberry wrote: > >I found a fascinating rant on the early use of Bishop Graphics, > >Chartpack/Letraset pre-cut tracks/pads, red vs. blue tape, US Mil Standard > >275-D, etc. at > > > >http://www.cia.com.au/rcsradio/rcscadph.txt > > Yes, fascinating. From my casual reading, I didn't see that the author > really recognized the supreme idiocy of red/blue tape. > > He talked about using register pins, but nothing about the concept of using > a single layer padmaster with separate mylar layers for top and bottom (and > innerlayer) track. > > from the file: > > >Now against all this in the 'olden days' we used to put the Black Pads > >on a separate piece of film which was 'pin bar registered' to our RED > >and BLUE tracks on separate sheets of vellum or as I said earlier > >you can put the RED and BLUE on the same sheet with the black pads held > >in registration for the other layers. > > Once a pin bar was being used, black tape could be used for everything, > thus making the photography cheaper and better. > > Mylar was a stable-base material, I used clear mylar for layouts. I used > frosted mylar to do the pencil sketches, and it was easy to tell layers > from each other. I used a black pencil. If I really needed to see a layer > clearly, I could always pull up the other layers, but usually simply > flipping them up, leaving them on the pins, was enough. Fast. I still can't > work as easily on large designs -- in this respect -- with the limitations > of monitor workspace. Consider what it would be like to have a E-size > monitor.... > > The reason for using a black pencil was that changing pencils took too much > time. Up until the time that Protel came out (and its prodigal son, Tango), > I could beat the CAD systems even with large designs, I was thoroughly > unimpressed by the figures that CAD sales gave, and do you think that the > systems were as good as the salesmen claimed? I just know that I was hired > to do manual designs for prototypes by companies with CAD systems because > the CAD systems took too long, they used CAD for production designs only. > But life moves on....
Well, the advantage of CAD systems was quickly apparent to me. The capability of comparing the netlist and the PC board, the capability of design rules checking, the capability of doing what-if experiments on layout, then trashing them and going back to the last try. These are what makes the CAD system work well. Also, being able to cut a section of a board out and use it as the start of another version, or to go back years later and make a few small corrections on a board and make a new batch. If you do that with mylar and crepe tape, you find a bunch of dried-up pieces of tape in the folder with the original artwork. That is not a good thing to have happen - the tape falling off the mylar. I still think that the old DOS program (I guess some people know it as Autotrax, but I know it as Accel's Tango) was the fastest PCB layout editor there was, and the schematic program did a better job at grabbing blocks and dragging them with all the connections moved in a very reasonable manner. I find Protel 99SE to be more cumbersome, and a little slower, but the reliability and freedom from bugs that trash the database and lose hours of work is worth a little slowdown. Jon * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
