Step 4: Installing the diodes
You will be fashioning pins to be inserted directly into the MPC board. Make VERY sure that you are able to attach them directly into female headers (sockets) labelled D12 to D8 on the microcomputer board. The larger MPC boards have a gap between pins D7 and D8; make the necessary adjustments to your installation!
Bend the leads of 5 x 1N4148 diodes to come out the the space at the bottom, with the cathode (-), banded side pointing towards the LEDs. The anode (+) end will attach to the micro's pins. If you find the wires too flimsy as a connector, reinforce them with a heavier wire.
Attach the cathode ends by thin wires to the LED's anode (row) ends: pin 12, row 1; pin 11, row 2; pin 10, row 3; pin 09, row 4 & pin 08, row 5.