Tips: Fabrication & Tools

October 1, 2007

John Swenson provided some helpful build tips for this project. I’ve included these tips in John’s words:

I start by putting in the parts, using a fin point marker or pencil to mark the holes for the end pins of each chip (1, 8, 9, 16, etc) and the polarity of each cap. This step is very important, it very easy to get confused when you are wiring on the bottom of the board, because it’s backwards from the top!

Then run the ground bus. You want to make sure its “tied down” in a few places to the board so it doesn’t move around. I just loop some bare wire through a couple holes in the board and wrap it around the ground wire.

Next run the “taps” from the ground bus to the ground pins. I do this by tinning a spot on the bus wire first so when you are connecting to the pin you are soldering to the solder on the bus wire which melts a lot easier than trying to heat up the bus wire itself. For the taps I use 18 or 20 gauge bar wire.

Then put in the power wires. I usually use 18 gauge for this. Sometimes I use bare wire, sometimes I use insulated. The bare wire is a lot easier to build a network with. Take one piece of wire that is the longest piece and put it in first, stitching it through some holes in the board; at least at the beginning and end. Run the other main wire, and then put in the taps.

For the signal wiring I like to us wire wrap wire, primarily because the insulation doesn’t “melt back” when soldering. This is very critical when doing close quarter digital boards. You can use other types of wire, but it’s important to use a type with insulation that doesn’t melt. If using wire wrap wire, you will need a special wire wrap stripper, a regular one will not work with wrap wire. The stripper is just a simple metal blade with a slot in it. You can get the wire in a three pack of different colors so you can use one color for clocks a different for input signals etc. Radio Shack sells it. I strip the wire to a fairly long length (1/4″ or more) then trim it down to a very short piece of metal showing, you do NOT want the uninsulated part accidentally shorting between pins!

For solder to chip pins I usually tin each pin first so there is a solder coating on the pin, then when connecting the wire to the pin you put a little blob of solder on the iron tip, physically touch the wire to the pin, then bring the tip to the point where they touch and let it sit there for a second or so, no more, and you have a nice joint, no need to add any extra solder. That way you don’t have to hold the iron, the wire and the solder.

Required Tools:

There are a couple of indispensable tools you need for this project. If you use wrap wire you need a wrap wire stripper. Radio Shack sells a cheap one and it works perfectly. You also need a vice to hold the board while you are soldering. You don’t want it running around the table top as you are trying to solder pins. I picked up a Panavise base and circuit board holder (parts 300 and 315) which worked very well for this type of project. Finally, you will need some form of magnifier. I bought a magnifying visor from Harbor Freight at John’s suggestion for $6 and I couldn’t imagine completing the project without it. Besides this, you’ll need a soldering station with some fine tips, long-nose needlenose pliers and a small flat electronics screwdriver, wire strippers, wire cutters, etc