I have a SD2. Took me a few months to get to printing stable. Main culprit was the bed. Going to glass was godsend. Then for few months battled the skipped steps mainly in Y some X. Replaced with black stepper boards with heat sinks no problems (until recently slight y step but after heater install, wonder if voltage issue)
Anyway it ran well until the heater failed, it was obvious, checked voltages. I bought resistors, cartridge, kapton,thermistors heat tubing all from QU-BD for about $34
Well I was leary of new upgrade and having issues with power or something. But it was painless I didn't even take off the hot end. just removed the rubber on the nozzle, unhooked thermistor and heater, Pulled the heater out with some pliers. Then with small dremel cleaned up and deburred the hole in the block and stuffed the new 12v 40w QU-BD heater in there. it fit snuggly hangs out about 1/2" on each end.
I resued the molex connector and soldered to the QUBD. It had like 2 feet of covered heater wire, I only used like 5" of it! I rerouted the wire and turned the block so the heater core is in front machine facing you going along the X. and the cable routes over the right side down the left into the molex and the thermistor goes in the left.
I tried wrapping in thermal fabric and kapton but it was a mess and looked crappy. I removed it and left it uncovered. It seems fine and looks good. I like seeing the thermistor and heater.
It heats up instantly but too fast and hit thermo limit of 215 in seconds. So in the Marlin file I lowered the PID_MAX to 160.
then ran autotune. It ran perfectly. I still need to autotune some more it swings within 10degress at the beginning of the print and sometimes randomly during the print. I do not see print issues and melts look even better then before.
I tried using heat laser gun to get temps but nothing seems accurate from the reflections.
Now after that I printed all night but my dreaded Y skip returned at layers 24+. Not as bad as before just in the Y then it resumes it appears in same position so it is either a skip in Y or band. I have new servo boards I can crank up some more AMP but it has been a while since I checked tension.
I have a spare QU-BD servo hi-torque I might replace Y and X with but I suspect the heater pulls more power
Either way it is simple and cheap upgrade and you just need the heater nothing else!