After discovering the semi-blockage in the support extruder, I carefully drilled it out with an appropriately sized drill bit and followed up with several pipe cleaners loaded with Mothers Mag & Aluminum Polish.
I carefully slid the heater coil back over the extruder (and tried to twist it as much as I could in order to keep it as tight as possible on the tube), re-attached the stud for the solenoid paddle, and re-attached the thermocouple probe.
Then I wrapped the woven fiberglass insulation back around the assembly.
The original foil was unusable, so I tried using plain old ‘heavy duty’ aluminum foil from the grocery store. It wasn’t as thick, so I doubled it up and did my best to wrap it as tightly as I could (using pieces of 3M high-temperature flue tape to hold it all in place).
The next step was to re-insert the pins for the heater and thermocouple back into the circular connector (I had pulled the pins out in order to more easily re-attach the heater and thermocouple to the extruder tube). Note that the correct insertion/removal tool is the Amphenol M81969/14-01 – it took me several orders from Mouser to finally figure out the right size.
I then used a few zip-ties to neaten up all the wires.
Everything got reassembled back into the housing.
Re-attach the motor drive blocks.
After putting the head back in the printer, I ran a few feet of support filament though the extruder to flush it out. Things were looking good… …until I attached the nozzle and tried running more filament through it. Just as before I started the extruder teardown, it jammed, kinking the filament off to the side between the drive wheels and inlet buffer. Seeing that the buffer was also now cracked, I said a few choice words and called it quits for the day.
Upon reflection, I figured that the extruder probably wasn’t the issue in the first place (assuming that I had done the rebuild correctly) and that the motor drive block or the nozzle was the culprit. I removed the motor drive blocks and set the head in the machine so that I could power it up and try feeding the filament through by hand. I was able to push the ABS filament through pretty easily, but the support filament I could barely budge. So I removed the support nozzle and put the model nozzle on the support extruder. Wonder of wonders, I was able to feed through the filament just as easily – the nozzle must be the problem! I reinstalled the motor drive blocks and sure enough, the support drive was able to feed support filament through the support extruder and model nozzle with no jamming whatsoever.
I’ll try clearing out the support nozzle with a 0.011″ drill bit (even though I know I’ve done so once already), and I believe I have a spare T12 support nozzle floating around in case that doesn’t work. At least I’ve finally found the core issue and I’ll hopefully have the machine fully functional in only a week or two. [insert something about 'famous last words']