2nd U3 Extruder Stepper Not Rotating After Zebra Hack - Fixed :)

[randyinla 14]

I performed the stepper driver hack (linked below) to help reduce zebra stripes in my prints the other day and all seemed fine at the time.  This morning, I was trying to load filament for the first time since the hack into the 2nd printhead of my U3Ext and the extruder stepper wouldn't turn.  If I lean in close to the extruder, I can faintly, barely hear the steps being sent to the stepper.  It climbs in pitch and back down again, just as if the extruder were loading the filament but it doesn't spin.  Seems the stepper commands are working but the voltage is so low, nothing happens?

 

Is the stepper driver under R103 the one for extruder #2?  That was the last short I made over the resistors.  Didn't take any longer than the other 4.  Looking at the photos I took after, it doesn't appear to be shorting anything else.  The SMD resistor didn't move etc.  I'll have to revisit it to check if maybe I shorted one of the pads to another.  R102 is the one where the SMD resistor fell off.  So if any of the steppers was misbehaving, it would kind of make sense it would be that one, though shorting a resistor is the same as shorting two pads with no resistor.  Sigh 🤨

 

 

Edited May 15, 2019 by randyinla

[randyinla 14]

Found the 1548-I Ultimainboard schematic for the U3Ext in the Ultimaker github repo and confirmed that U13 with R103 is the stepper driver for the 2nd extruder.  

[randyinla 14]

Fixed it.  After taking off the cover and putting on my jeweler's magnifier goggles, I could see from the side that the wire I soldered onto the pads wasn't touching one of the pads.  Must have desoldered the SMD resistor as well, I guess.  Removed the resistor completely, cleaned the pads and used a different tiny piece of solid wire and made a proper connection.  2nd extruder working fine 🙂

 

WHEW! 😅

Edited May 15, 2019 by randyinla