And here it is-
This is located on the unused second extruder drive board socket.
It bridges the +5 to the +Vmotor connections with a 1N4002 diode, cathode to the +Vmotor as shown.
An MUR120 or a Shottky diode would be better (lower forward voltage), but this works well enough.
Whatever you use should have a rating of at least one ampere and 50 volts to be on the safe side.
I just happened to have (literally) about a thousand of these sitting around.
I soldered it onto a pin header strip and then just plugged it in.
If you were careful I suppose you could insert the rectifier leads directly into the socket, but they might be a bit tight and could easily ruin the connector if you ever wanted to add a second extruder later on.
Better to use a pin header strip (0.1" centers, 0.025" square pins).
I don't know, I have been using some pretty cheap filament lately.
Speaking of cheap filament, I was printing this thing out of PLA last night and was using cheap filament ($18 for a kilogram reel).
Oh my Lord that stuff is hard.
My MK8 extruder had a really tough time gripping it and it kept slipping.
I think it's time to change over to the E3D Titan setup I bought.