About the cable
The thermocoupler (see Fig 1.1) is brown in colour and screws into the back of the aluminum heater block with a hex nut connector (see Fig 1.2) and runs to the motherboard through the main extruder 
bundle.
What can go wrong
This part is the most fragile within the machine. It can also break through use and get damaged along the wire at points where it is bent sharply. For these
reasons Bilby 3D manufacture thermocouples in Australia
About the BilbyCNC thermocoupler
Our new thermocouplers have numerous extra features that make it
stronger and more durable including:
Resin reinforced sensor- to hold wires firmly inside the sensor probe(3mm hex screw). Many customers found this was where the thermocouplers broke during use.
Thicker (3 strand) wire– The Makerbot thermocoupler had a tendency to get damaged from crimping along the wire and a high rate of partial breaks that result in false temperature readings. The stronger wire will help eradicate this.
Plug Connectors– There was a high rate (especially in the push pin style motherboard connectors) of the thermocoupler just falling out of the motherboard connection. We has terminal ends attached to help keep this connection more firm and dependable.
Fitting a thermocable
1. Unscrew the extruder assembly from the gantry.
Unscrew the fan screws at the front of the extruder/s and remove the fan/s, small black spacers behind the fan/s, and the aluminum heat sink/s. You can now undo the two screws that are under the aluminum mounting block (the long block in Fig 1.5 which depicts Replicator 2x. Replicator 2 has the same fan, spacers and heat sink with a different filament feeder system behind it.) and lift out the heater block assembly to provide easier access to the thermocoupler/s.
2. Remove old cable from the Heater block and attach new one
Unscrew the hex connector from the heater block and screw in the new one.
IMPORTANT : try not to twist the cable or damage it when screwing in.
Fig 1.6 shows Replicator 2x where the thermocouple goes in from the top
and Fig 1.7 shows the Replicator 2 where the thermocouple goes in from the back.
3. Change wire path : Replicator 2X
Bilbycnc recommend wiring the thermocoupler straight up around the outside of the
filament feeder system past the drive wheel viewing window, so that it runs around the side and over the top of the filament feeder. This path has less severe bends and thus is less likely to damage your cable than the original path. Fig 1.10 at the bottom of page (prototype thermocouple shown in picture with black sheathing)
4. Connect the new cable to the motherboard
Turn your machine on its side and remove the plate protecting the motherboard. Connect the cable
to the motherboard (note : the cable has a red and yellow cable. If you can not see this easily pull the gold coating back a bit). The motherboard labels the connections “red” and “yellow” (Fig 1.8) You will find that our new connector ends make this connection more secure and that the red cable it also labeled (-) and the yellow (+)
5. Test it working
Run “load filament” and test it is all working. You can do this with the heaterblock just sitting in place—does the machine have any errors on startup? All good? Then fit it properly.
You need to remove the old cable and insert the new one into the extruder bundle.
This will require some zip tie removal and threading.
