50 mil down ought to do the trick, if you can make it fit; most board houses I've worked with require 25 mil copper clearance and 75-100 mil hole clearance from the edge.
As far as chips fitting side by side, chips with a multiple of 4 pins (16, 20 being the most common) can usually fit. The reason 14-pin DIPs have that problem is because their bodies extend significantly beyond the outer pins, whereas those with an even number of pins per row are usually nearly flush. > On Feb 28, 2014, at 12:39, Crusty OMO <[email protected]> wrote: > > Paul, The drawing does not show actual trace width. > > Yoda, Those shorted pins above the 5V regulator are for an optional 12V > regulator. I agree, the 5V reg should be moved a little right. > > Dave, Yes, the holes are close to the edge (aren't we all?). > > Right, great questions, let me describe the board. > All the traces between the S-100 and Buffer IC's are 12mil with 13mil > spacing. Traces that tie the 74LS245 chip directions to ground or vcc are > 8mil. The board is ready to go as a slave board (ie memory, i/o, etc). If > you need to convert it to a CPU board, the buffer directions need to be > reversed, the 8mil traces need to be cut, jumper wires added. The +5V and > Ground traces are 50mil, they extend up the right side of the board and feed > every 4th hole (only the top layer is shown, the GND is fed to every 4th hole > from the copper side). From these holes, bus wire can be used to feed a row > of 300mil chips. The +8V is also 50mil to the regulator, but goes through a > short 25 mil "fuse" trace. This way a short will not fry the whole trace and > damage the gold plated S-100 pads. The +16V and -16V use 35mil traces and > go through a short 25mil "fuse" trace too (I should reduce this to 20mil). > > The 5V regulator is at the same location where Andrew placed it on the > Unbuffered board, but I agree, it should come a little to the right, say > 100mil. Above it are provisions for a +12V and -12V regulator. The power > traces reach those pads, but you don't have to use them. There's plenty of > holes around it so you can easily install any other IC there around the > specialized holes for the regulator. This regulator does not need to move, > it will never require a big heat sink... I hope. > > The top row can be made like this, but I agree it's a little too close... I > think I'll shift everything down 50mil and sacrifice a row on the bottom. > > The 74LS245 chips can be placed side by side (even on sockets). I've > checked this out with a dozen different chips from my junk box, it works for > all of them. I think the 14 pin chips have this problem, especially those > from 1970's. I can redo this test and take photo's if that helps? -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
