On Fri, 18 Mar 2016 19:36:14 -0700, you wrote:
>Separate discussion.
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>Im not planning to tackle this anytime soon, but I have been slowly acquiring parts and am hoping after Ive gained lots of experience to one day build a Mark-8 replica.
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>I expect this would be a very challenging project, which is why its long in the future. But Im always interested, always reading and learning.
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>Jon Titus, the creator, arranged with a New Jersey company to produce board sets hobbyists could order, similar to the TVT. Those obviously are ultra rare unobtanium now, however, Im guessing the presence of circuit board patterns in the construction details (http://bytecollector.com/archive/mark_8/My_Mark-8_Info/Mark-8_Construction/RE_Mark-8_Const-NEW.pdf -- page 25 or so) indicates it was at least possible some hobbyists went and made their own, correct?
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>Im wondering what differs in etching with double sided projects? And when they say the holes werent plated through, does it mean what I think it means (there would be a copper connection between a trace on one side through a hole the component is soldered into through to the other side?). Not sure Im understanding how the connections would be made from one side to the other.
Alignment between top and bottom is critical. The spacing between
lines and the size of the lines themselves is often given by two
numbers (in mills) 10/10 meaning .010 thick lines with a minimum
spacing of 0.010 inches.
Plated through holes are a normal part of double sided boards, and the
plating is also used to connect inner layers on multilayer boards. The
main problem with plated through holes in the home environment is a
combination of the number of steps needed, the unpleasantness of the
chemicals, the cost of the same, and the shelf life.
while it can add an hour or two depending on the complexity of the
board, the eyelet or the laced wire method is one solution to the
problem. Commercial conductive ink solutions may or may not be a good
idea depending. Never tried them myself.
I've done home built boards that are good enough to handle 100 pin 0.5
mm spacing quad flatpacks, although they are a pain to do and not
always a certainty that they will be done properly.
For some boards, I find that I needed to go finer and pack more chips
on, so that required a 6/6 process, which I can't do. A commercial
board producer makes them when I need them; but for more conventional
designs, or prototypes, I still (mostly) make them myself.
Photoetch can always be nicer than toner transfer, the problem is
getting a good dense pattern, and properly sensitizing the boards (or
buying them sensitized, rather expensive).
Alignment is also critical, and will be more critical the smaller the
trace and via size.
Harvey