the blue wires on the larger pcb go from and to as follows:
pin 6 of the edge connector to chip D6. the pin on D6 chips is gate 3 output (3Y) which is pin 8 on the chip.
pin 7 of the edge connector to chip C6. the pin on C6 chips is gate 3 input (3B) which is pin 9 on the chip.
both these chips should be a DIP-14 package and 74LS00 chips.