Various motors, switches, sensors and heaters around the machine have wires which are brought through various holes to the electronics bay and connected to the RAMPS. The moveable bed starts by using a ribbon cable, constrained by a plastic strip; once the connection is made to the frame, it changes to a couple of wires for the thermistor and another couple of higher-rated wires for the bed heater (which can draw as much as 10A). The extruder and the X motor and limit switch also use ribbon cable to connect their moving parts to static parts. They actually share a single cable, with some wires terminating at the motor and some continuing through cable grips to a D-plug which plugs into the extruder. This picture tries to show both cables:

The X/extruder cable runs from the extruder connector across the foreground, via the X motor, then down and back up vertically (to deal with Z axis movement) before going over the top to connect to the electronics. The Y cable can be seen on the base emerging from under the Y carriage, terminating at a cable clamp and being transformed into pairs of heater and thermistor wires.

So the following wires arrive in the electronics bay:

• Power supply (yellow and black; 6 wires)
• PSU enable (green: 1 wire)
• Heated bed heater (blue and brown; 2 wires)
• Heated bed thermistor (black; 2 wires)
• X/extruder ribbon cable, carrying:
  • Extruder stepper motor (4 wires)
  • Extruder tip heater (2 wires; short red and black extensions)
  • Extruder tip thermistor (2 wires)
  • X limit switch (2 wires)
  • X stepper motor (4 wires)
• Z limit switch (red; 2 wires)
• Z stepper motors (multicoloured; 8 wires, because there are 2 motors)
• Y limit switch (green; 2 wires)
• Y stepper motor (multicoloured; 4 wires)

You can see them all connected:

The extruder heater wires had to be extended as I cut the ribbon cable a little short. The loose black wire is a guard loop to reduce interference in the ribbon cable; it needs connecting to ground when I can work out somewhere better to connect it than screwing it into the power connector.

I had a bit of a hiccup when I realised that the Molex connectors I had bought to connect the wires to the pins were fine for a single row of isolated pins, but when pins are in groups, they don’t fit because they are 2 or 3 pins wide. Fortunately, a bit of cunning wiring, the removal of some extraneous pins and the filing down of some of the connectors made it so I could squeeze everything in.