RAMBo Blown Fuse / Short Circuit

First, which fuse on the RAMBo?

  1. The HOTEND FUSE, labeled F3, is the tiny 5A fuse beside the power input to the RAMBo and located closer to the large 15A auto fuse. 
  2. The MOTOR FUSE is the tiny 5A fuse, labeled F2, is located near the capacitor and farthest away from the large 15A auto fuse.
  3. The BED FUSE is the large 15A auto fuse, labeled F4, is located close to where you hook up bed heating wires.

**Be very carefule not to damage the tiny fuse holders when removing the fuse. They are fragile **


Power off and unplug machine before working with electrical.


If you blew a HOTEND fuse, F3?  

  • check for short circuits in wiring and heater cartridge wires, etc.
  • test for proper ohm reading, old bowden ~3.4ohm, HE280 ~3.9ohm
  • it's rare, but possible for heating elements to give an ohm reading, but short after power is applied (just something to keep in mind)
  • stray wires or touching hotend heat sink


If you blew a MOTOR fuse, F2?  

  • This is not very common. Check for stray wires at connectors
  • check for loose connections or damaged wires to the motor
  • check motor for free rotation
  • check stepper motor coils (both coils) for resistance to make sure there isn't a short circuit



If you blew a BED fuse, F4?  

  • check for short circuits in wiring
  • check solder joints on bottom of heat bed
  • check bed for an ohm reading (not short circuit)


electrical power circuit


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