I am also curious, you said you were using like 3 rolls of filament that sometimes worked in the other printer and sometimes work here...  Just as a couple of off the wall checks, what are the three filament spools?  Where did they come from and what color are they?

Three came from Solidoodle; one came from an unknown source; three are Octave.  I switched from the Black from Solidoodle to a white from Octave to eliminate the "Black problem" (even thought I do not believe that to be the issue).

130C at the tip of the nozzle with a contact thermometer

No grease on the bushing that I printed to help the filament come through the rear hole

No, the tensioner arm does not move.  I put my fingers on it to see if it was moving even a little, but no.  Note that I have now reduced the tension there, by moving the adjuster so that almost all of the screw is now inside the spring.

With the indicated/graphed temperature at 200, if I extrude and then pull the extruded plastic away, the nozzle continues to emit a small amount of filament ooze (perhaps 1/2 inch per minute).

I'll give it another try.  Maybe the tensioner spring was too tight.

Too tight could be a problem if the spring is bottoming out.  I see the arm move back and forth a fair amount as filament goes through.  Do you ever see the spring run out of space between coils?

I have backed the spring out so that the adjusting knob just allows a hint of the screw threads to show

  If you increase the temperature while the printer is idle, does a little filament ooze out, or does it still stay in there?  For me, that is generally the best indicator of a partial clog.  When it is all the way clean, it oozes at 200 or above, when it is partially clogged, no oozing.

So, something is causing the filament to stop feeding.  I have the pressure spring set up so that there  is about 2 mm of the screw visible, so it is fairly tight.  Not sure if this is a good thing or a bad thing. Too lose, and it will not feed.  Too tight, and it might occasionally cut the divot.

Could be due to variations in the filament, but if you want to hypothesize arbitrary variations in the filament, then you might as well sell your printers.

Not sure what to do next.  As is almost always the case in my house, the Solidoodle remains stunningly unreliable.  I am SOOOOOoooooo frustrated.  All I wanna do is print!

Not as extreme.  I haven't had much trouble with clogging, mostly with the wire connectors.  Handling it to deal with the connector eventually crumbled the cement, and moving the wires around weakened the nichrome.

Same here. I had 2-3 clogs that required removing the hot end, and just handling the wires that much crumbled the cement and broke the nichrome.

Ironically, I haven't had a clog since. Ha!

In my experience, the hot end has been mostly ok if you never touch it.  If you have to take it off to deal with an occasional clog, the wiring is going to eventually go bad.  I finally ditched it because the nichrome and cement just isn't robust enough.

The acrylic performed well enough, but it's a nuisance if you have to get at the hot end.  Unlike the video on Vimeo, the fit was tight enough on the PEEK that it wouldn't come out the front.  I also like having the nozzle, heater, and thermistor all embedded together in a single piece rather than stacked and taped together.  I also wanted to replace the acrylic because I figured a printed extruder would provide a good starting point for built in mods like a standard mounting system for accessories.

The only time I had chronic difficulty with extrusion a new PEEK and nozzle cleared it up.

Nobody else seems to be having as much trouble with hot ends as you.

Interesting.  I saw you and Tim and Lawsy and others replacing their jigsaws and their hot ends, and figured that most folks fairly quickly realized that the hot end (and the Z axis and the warped bed and the filament feed) was a weak point in the Solidoodle design.  I figured that this was just how Solidoodles are.  Why are all of you replacing the hot ends, unless they were giving you trouble?  Is your trouble different than mine?

The two recently failed new Solidoodle hot ends were clearly failures, and Solidoodle is sending me new ones.  We will see how that works out.

Hard to know what might be different between my printers and everyone else's.  If you have questions, I'll try to answer them.  For example, I wondered whether a "hot" 12 V power supply might make the hot ends on the problem printer burn out.  Turns out that printer's 12 V is in fact 0.3 volts above the other.

John, were your replacements entirely new hot ends including PEEK?  Have you tried filaments from other sources?  Nobody else seems to be having as much trouble with hot ends as you, but your setup can't be all that unique.