Extruder Problem

I have suddenly developed a problem with my extruder. I have been printing OK nearly every day, but when I started a print off today it started OK then all of a sudden after about 30 mins into the print the extruder motor started buzzing and the filament stopped. The motor seemed to be quickly going backwards and forwards causing a buzzing sound. When I tried to control the extruder from the LCD panel it did not buzz but it only retracts. On retract, it retracts (I have a Bowden setup) and on feed, it retracts as well. The filament only goes in one direction.
I tried adjusting the voltage on the stepper, I then changed the stepper. Finally I swapped over to another extruder with another motor.
If I try to control the extruder manually from either from the printer LCD panel or from Repetier Host using my PC it still retracts on both feed and retract.
I am running an Arduino mega 2650/Ramps 1.4 with a Wade extruder. My Arduino firmware is Repetier but was last flashed 2 or 3 weeks ago. I have done many prints since then. The eeprom is disabled.
Any advice where to look next before I swap out the Ramps or the Arduino board?

I had a similar problem with bad connections on my stepper wiring. I unplugged and reinserted the connector on the ramps board and everything was fine. Has happened a couple of times, but works fine now.

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Macarduino wrote:
I had a similar problem with bad connections on my stepper wiring. I unplugged and reinserted the connector on the ramps board and everything was fine. Has happened a couple of times, but works fine now.

I have swapped out both the stepper driver and also the extruder + motor. This obviously has a different connector and plug fitted.
I am wondering if it might be a fault with the stepper driver pins on the Ramps board or a dry joint.

Found the problem ......................... a duff stepper driver, which I had mistakenly replaced with another duff stepper driver !!!