So good news, I have the Print End together on the Printer.
It’s all wired up, and appears to be good. Before I mounted the hotend, I ran some of my PLA plastic through the extruder and took a look at the steps/mm. Which means that if I ask for 1mm of plastic, I actually get 1mm of it. Surprisingly it was dead on without any changes needed. I even had the extruder wired up in the correct direction first try.
The thermistor is responding well, it appears to be accurate. I heated up the hotend in steps and kept an eye on it. I ran the temperature up to 180degC eventually and I was able to push by hand the plastic through and extrude my first pieces of plastic.
I then allowed the extruder to push the plastic through, and everything seemed perfect!
The large aluminium thing on the left is a laptop 5V fan to keep the top of the J-Head cool.
I also had to get creative with mounting the spool of PLA.
Spool Mounting