May have shorted thermistor pins with 12v, How to check VSSA Fuse?



  • Okay so I am scrambling to get my final assembly put together for my senior design project but I ran into a rather large problem.

    I was unplugging my gantry while will keeping the heater block on and active to heat up so I could fully loosen everything. So my thermsistor jump and seen that my cooling fan pins were touching my thermistor pins. Now both the hotend and bed temps on the web control show error. I assume it has something to do with the VSSA has no connection to ground? I am looking at the schematic, but can barely understand it. It appears to test, I should see if there is any resistance between the F1 component on the board right? I am killing to get this done by this Friday which is definitely pushing it and can use all the help I can get.

    The datasheet is below:
    http://datasheet.octopart.com/MC36221-Multicomp-datasheet-21398636.pdf

    Thanks in advance!


  • administrators

    Easiest is to measure the resistance between the VSSA pin of any of the thermistor connectors and the GND pin of any of the endstops. If the VSSA fuse is intact, it should be around 2 ohms. But it sounds as though you have fused it. You can bypass it with a glass cartridge fuse if you don't have hot air soldering equipment.



  • @dc42:

    Easiest is to measure the resistance between the VSSA pin of any of the thermistor connectors and the GND pin of any of the endstops. If the VSSA fuse is intact, it should be around 2 ohms. But it sounds as though you have fused it. You can bypass it with a glass cartridge fuse if you don't have hot air soldering equipment.

    Thank you for the quick response.

    I jumped pin 40 on the header and the gnd pin on one of the endstops, still resulted in 0 ohms. Sounds like I will need to get a fuse to get my by until after my presentation. Would I just solder either end of the cartridge to the pads? In a sense jumping the pads through the fuse?



  • Thank you so much! soldered in a cartridge and it is alive! I will order one of these here soon to replace down the road.



  • If VSSA to ground reads 0 ohms, then the VSSA fuse was fine.

    If it reads open circuit or a very high resistance, then the fuse is blown.

    Also you shouldn't ever jump VSSA to GND without using a fuse, or else the damage could be a blown processor instead of a blown fuse.


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