Yay! It still prints PLA… Had to disable half the ramps, and the LCD no longer works… But it prints… So I think the idea now is to print out (I know it’s bad) OB1 parts from PLA just to get it working I’m sure the PLA parts will hold up to printing the needed parts on the OB1 then I can swap them out.
I might swap the ramps out again sometime… Might just leave the I2 as a PLA printer… Seems it likes to print PLA a lot better anyway.
Check the 5V rail voltage without USB plugged in. You can check 5V from one of your end stop leads if your ramps is hard to get at. If the voltage is low then the mosfet may not have been driven hard enough and only switched partially on with high resistance causing it to heat up excessively and eventually fail. A symptom of low voltage is a dim LCD when USB is not plugged in… Low voltage is caused by the Arduino on board 5V regulator going out of spec… In my case maybe caused by accidentally shorting end stop power rails(maybe more then once) during build…
PEB3DPAC
What is PEB3DPAC ?
Problem Exists Between 3D Printer And Chair.
… Thanks Anthony, although probably true. I do get pretty impatient with this machine… But most the time I stand… So ha!
heh, it wasn’t meant as an insult. Generally though, if something happens more than once like this it’s generally something the user is doing wrong. 
Don’t worry, you’ll figure it out - btw which part of the RAMPS is blown up? Is the microcontroller/arduino fine?
Sall good I didn’t take it as an insult :D. It’s hard to convey sarcasm through text.
Far as I can tell its just the HB MOSFET I haven’t taken the time to take it out of its enclosure and test everything yet, I just let it limp through the last print of PLA. (Is somewhat hard without at least a small heat source under it).
I’m sure when I get the time I will order some mosfets for for the boards I have and perhaps modify them a little. Maybe thicker traces? Might have also blown a diode as well but it doesn’t look like it.
The mega is fine I ran a PLA print through it last night. And all of the stepper drivers are good (thank god) last time this happened it blew all 4 stepper drivers and the mega.
Did you check your 5V rail on the mega ? Mine also functioned fine, though turn heatbed on and Mosfet shot up to 150C+. Plug in USB Mosfet temp returned to something a little more sane. Checked 5V rail and voltage was 4.5V. Replace the Adrunio with a spare that was showing a solid 5V rail and everything was fine.
Ya no I haven’t checked that yet. I might get some time today to do it. Right now though as long as it prints PLA I’m fine with it limping along tell I get time to fix it.
Man the hits just keep coming, now I have a loose connection inside my extruder stepper…