I had similar problems on an A8. In my case the problem was a poor ground connection on the power supply. I managed to fix it by soldering on some ring terminals for all my wiring going to the PS screw block, and tinning the leads going into the screwposts on the printer circuitry.by Spiggles - Reprappers
Ramps Mega is what I have experience with, any particular reason you don't recommend it? I could order a replacement logic board of the exact same make. They aren't expensive, but the stepper drivers are integrated on the pcb so if a driver burns out I am facing the same problem. I have decided to go with the Marlin firmware for the reasons you mentioned (strong documentation) and it looks likeby Spiggles - Reprappers
The MOSFET modules I got were marked www.biqu.equipment on the pcb. I ordered 2 and one of them didn't work out of the box. The other lasted about 4 or 5 weeks and then died. This is what I use now; It is overkill for my needs but better too much than too little. That being said, you might want to throw an inline(series) fuse in the circuit on the off chance the heated bed shorts or somethiby Spiggles - Reprappers
Hello all. I am new to the community but I have been working with electronics and 3D printers for a few years. I recently got a super cheap 3d printer from China. Cheap in price, but actually produced good prints. That is until a clogged hot end killed the stepper motor driver on the main logic board. Long story short, I am going to replace all the electronics with a Mega2560 and Ramps 1.4 Shieby Spiggles - Reprappers
I have had mixed results using external mosfets. In particular, two failed MOSFET modules from China. I recently switched to a solid state relay module and so far that has worked well for me. I converted an old ATX power supply as the external power to my heated bed.by Spiggles - Reprappers