May use help!: Extruder won't work anymore :? , Ramps 1.4 (1 reply)

I have a DIY Prusa i3 2020, that I assembled personally , with internet reference, ,Every thing was working fine for extruder , it was moving fine , until m first try to clean the nozzle for the first time, a heat smoke came out of the nozzle , and a dripping plastic came out of heat block , after emergency power off , the extruder won't motor won't rotate , I tried these
1- tried connecting motor to another driver say the X's , it worked well --> concluion: the motor is working fine
2- tried the old extruder stepper on another axis , it didn't work --> conclusion: old stepper driver was fried , yet extruder driver does not work with another driver
3- tried replacing the stepper driver with an already working driver of one of the other axes' , motor didn't work either
4- tried changing Ramps shield with another one , that didn't help either
5- bought a new arduino , extruder didn't work either , with old or with new Ramps ,
6- tried replacing extruder 2 as primary extruder , it didn't work , or may be I am bad at Marlin and Arduino coding so may be I did it wrong , so It didn't work
7- tried a working stepper driver on every arduino and Ramps switch try , It didn't work
and it seems that I am ran out of ideas
I think may be the extruder side of Ramps may be the problem , but that was to be solved with changing either arduino or Ramps or driver or the three , which didn't !
even hanging the whole circuit does not move axis
I am using Hardware: RAMPS 1.4 ,Arduino Mega 2560 , Software: Marlin v 1.0 , and Arduino v 1.6.5