The problem arises when turning on the heated bed.
I took my multimeter and it shows that the two D8 screw terminals have a potential difference of 12.02 V, exactly as it should be. My heated bed has a resistance of 1.1 Ω (including the wires), again as it should be. This results in a current of about 11 amps, within the specification of the fuse. I'm also cooling the board with a fan.
Despite of this, the polyfuse overheats within 5 seconds of turning on the heated bed. It becomes far too hot to touch and it shuts off power to the heated bed. The three MOSFETs, however, remain cool.
I reduced the duty cycle to 33% by changing Marlin firmware settings. My multimeter now reads about 4 V and the current should be about 3.7 amps. Despite of this, the fuse STILL overheats, albeit rather slowly.
What is going on here?:S Has anyone ever had a similar problem? Should I replace my RAMPS 1.4 board (admittedly, it was the cheapest one I could find on eBay)?
I would very much appreciate your help :)
I took my multimeter and it shows that the two D8 screw terminals have a potential difference of 12.02 V, exactly as it should be. My heated bed has a resistance of 1.1 Ω (including the wires), again as it should be. This results in a current of about 11 amps, within the specification of the fuse. I'm also cooling the board with a fan.
Despite of this, the polyfuse overheats within 5 seconds of turning on the heated bed. It becomes far too hot to touch and it shuts off power to the heated bed. The three MOSFETs, however, remain cool.
I reduced the duty cycle to 33% by changing Marlin firmware settings. My multimeter now reads about 4 V and the current should be about 3.7 amps. Despite of this, the fuse STILL overheats, albeit rather slowly.
What is going on here?:S Has anyone ever had a similar problem? Should I replace my RAMPS 1.4 board (admittedly, it was the cheapest one I could find on eBay)?
I would very much appreciate your help :)