Been thinking about the current passing through the Ramps terminals for the bed heater, and heating problems some users have had with connectors, etc.
So got me thinking, why not move the bed mosfet from the Ramps board, and place it on a heatsink, and ( if I understand correctly that the Mosfet controls the Ground line to the printer ) connect the bed directly to the 12V+ PSU, and have the mosfet control the ground to the bed.
The benefits that I see in this are :
I could use a separate PSU for the bed, as long as the ground is common to the ground of the PSU running the Mega and Ramps
I have space to add a decent heatsink to the Mosfet
The Ramps pins will have much less current, so much lower risk of damage to Ramps.