I have bought a second hand printer about a month ago (was the best option for me when cost is concerned). The vendor owns a hobby shop and had this printer he built for sale.
The printer is a coreXY configuration, running on a RAMPS 1.4 kit. It is also running on repitier firmware. I use Cura to do the slicing.
The printer printed fine for a wile with no (observable) problems. A few days ago when I started a new print I could smell electronics burning and I observed the heatbed temperature was increasing past the set temperature of 45C. I turned the printer off at the pain power supply and switched it back on. When I turned on the heated bed it did not heat up at all. Reading other forums I understood that the MOSFET was most likely the culprit (I have measured the fuses and they were functioning correctly). I replaced the MOSFET on the RAMPS board and carefully measured everything around it to ensure that I had not accidentally shorted something in the process. I replaced everything and turned the printer back on. Everything worked fine, the heatbed LED on the RAMPS was off. I turned on the heatbed and it heated up. Soon, though, the heatbed temperature increased again passed the set temperature and I immediately turned the main power off. I disconnected the heatbed and measured it and it had a resistance of less than 2 ohm. With the heatbed disconnected I turned the printer on and immediately the heatbed LED on the RAMPS was on.
I have printed a part, with the heatbed disconnected, and everything works fine (except the heatbed).
Will I need to replace the RAMPS board? Is there any thing else I can try and do before replacing the RAMPS?
