Hello...
I finnaly managed to open pcb file.
As electronics is my area I can say folowing from what I see in board.
- used FET is PH7030L and has RdsON worst case 11mOhm (at 5V on gate) So if I assume 10A for heatbed that's mean over 10W of heat dissipation. And there are two FETs close together. So the board will overheat here. But as the heater doesn't work all the time in most situation the board should work fine just with some fan for cooling.
- There are no exact part number for MOLEX connector used in board. But I find only one MOLEX PCB connector rated for 5A per pin but doesn't fin on board. I find two choices and one has 3A per pin rating and other has 4A per pin rating. I do have 4A per pin type. From datasheet and experience I can say that connector will melt with 4A per pin current. Of course not instantly but over time. Declared resistance of contact is 10miliOhm so at 10A current each pin develop 5W of power dissipation. So 20W per connector.
- I don't know the thicknes of cooper on board and if it's standard 35um then the width is just ok for 10A. But there is more than 10A (Extruder, bed, and stepers). If board is with 70um cooper then this is ok.
- The weakest link is power screw terminal. The solder pad has thermals so the cooper area in this point is way to small to handle all currents. If the boar has 70um cooper then thermal arrea jus barely fit for 10A but nothing more.
- shamed that over so much iterations of new boards the 5V backfeeding problem isn't solved yet. Just two diodes.
Don't understand me wrong. The board is othervise ok, but have some isues that should be solved.
In my board I will do:
-Install 2 diodes to prevent backfeeding 5V to usb. (this can destroy USB port!)
-Solder heavy wire from FET sources (left 3 pins) to PSU
-Solder heavy wire from FET drain (tab) to heatbed/extruder
-Power heatbed/extruder directly from PSU not from onboard pwr connector.
Slavko.