Here we have the combs laid out on the board, cut to the correct length with a pair of wiring cutters and super-glued in position. Sorry! Some are a bit crooked aren�t they! Also note that I�ve identified the pin <1>s� and the IC numbers to aid identification when things start looking complicated. The picture below shows a close-up of the track cuts and combs surrounding IC6, the 74xx14.
I�ve included the picture below to help anyone who might still be a bit unsure about just where the track cuts need to be made on the board. Note how the corner of the IC socket pins have been bent inwards slightly until they�ve been secured in position by soldering.
The next part of the construction is to begin the wiring itself. Power wiring first! Now some people like to use a heavier gauge wire for the power connections. I sometimes do this myself, but really think of it as being a bit unnecessary with low power devices if each IC has a SEPARATE power wire and decoupling capacitor. Note that I like to distribute power from the tracks on either side of the board - the 0V from the left hand side (looking at the back) with the +5Volts on the right. This way the power wire lengths are kept to an absolute minimum.
Before we carry on with the wiring, here is what the board looks like from the front. NOTE that the socket used for IC3 in the above picture is NOT the turned- pin one mounted the wrong way round in the picture to the right! Also you may also noticed my first error if you are observant (which I of course wasn�t). The socket for IC7, the 74xx32, is incorrectly a 16 pin device - it is in fact meant to be 14 pin! Lucky that it wasn�t the other way round as I was able to ignore the extra 2x pins...
And here we have it! The board�s first wire wrap. Note that the wire has been secured to the +5V rail (i.e. the RH side of the board) then routed down the first castellation and wrapped onto pin 16 of IC3 the 74xx139. Is is as of yet unsoldered at the IC socket end.
Most designers like to filter their board at the approximate rate of one capacitor per IC package. In the case of our project board, this ties in well with one pair of power rails per- IC package too. Note in the picture on the left how the decoupler (customarily 0.1uF) is mounted in the centre strip of the three between IC packages 6 and 7. An extra track cut will be needed too as shown. This was one of my errors in this project (shame on me!) I forgot to cut the track on one of mine..
