Hi Mike, The loose left wire is for segment F. The center wire is for segment A. The right wire is for segment B. Suggest re-soldering all three wires.
You can use an ohmmeter to check for continuity from the F, A & B wires to the the F, A & B segments for the 4 LSD (right) digits at the LEDs mounting angle header. From the front of the DR7 pin 1 is the far left angle header pin. From the F wire there should be continuity to pin 22. From the A wire there should be continuity to pin 21. From the B wire there should be continuity to pin 20.
I don't know why DF4NW decided to use the 3 wires as the F, A & B signals are already on the aftermarket LED circuit board. Likely to make the new circuit board look more like the originals LEDs installation.
73
Roger VE7LB
