Grumpy_Mike:
Sorry but you can’t tell much from that, it is quite a lot of a mess.
yeah, i guess looking at it in one go and not having "stepped through it" is pointless.
it was more to do with keeping track of making the connections WHILE doing it, matching the colour-coding with the diagram below to show which OR goes to which NAND and then subsequently to an AND.
the chips themselves are actually symmetrical - each quad has the (two) inputs on the outside, and the output is in the middle (on the "inside" 
!).
the top half is one full-adder, and the below is the other one, or rather, the one below (from pin 1 to 6 is for "bit 0" and the other side (top half) is for "bit 1" - making a 2-bit full adder.
Grumpy_Mike:
When doing schematics of logic circuits you normally show the gates and any logic circuits as blocks with labled and numbered connections. The positioning of the connections on these blocks is done to minimise the number of wire crossing. What you have posted is just as useless as a Fritzing diagram.
yeah, i guess it's not really a proper schematic diagram - but a physical circuit layout for doing the actual wiring.
infact using SCH-express, they showed the logic gates and not the DIP-14 layout, which i had to make myself for the above "diagram".
i guess the real schematic is actually the small diagram below.
Grumpy_Mike:
The output LEDs do not show anything connecting to the cathodes, and what is that circle in the anodes denoting? Also you seem to hav no decoupling capacitors at all.
the circle was in lieu of using yet another colour, so it was just to indicate which pin was for the 'SUM' output for the LED.
and i obviously got "tricked" by my own diagram, forgetting about the decoupling caps as well !
they're on now though... 0.1 uF for each chip, and another 10 uF on the power rail itself.
Grumpy_Mike:
Basically I think you wired something wrong. I hope you are not doing any wiring with the power on.
nope, it was a s l o w process over a few days (for each colour) to get each wire just the right length and to position it as tight as possible - it really looks quite nice if i may so myself !
Grumpy_Mike:
Did you do it all at once and then applied the power? If so build up your circuit one part at a time and check it works before proceeding.
i guess that would have been better, ensuring the logic is coherent before connecting it to the next one, but then i'd have to tie every unused input to GND and i didn't have that many free jumpers.
i've tested the outputs using an active buzzer (easier than an LED) but found that some outputs really had too small a current to even make the buzzer sound !
i really think the four quad-gates are fine and the issue is with the single OR gate(s) at the end, which is not using a chip but two transistors, or diodes for the other OR gate (2nd full-adder).
