Single direction movement (not an endstop problem)

So I'm running ramps 1.4 with Marlin firmware, and I'm getting a strange issue. Whenever I move my Z axis, it only moves a single direction (up). It moves the same direction regardless of whether I sent an up or down command. It's not an endstop issue, and I'm fairly certain it's not a hardware problem (though I could be wrong). It definitely not a driver since swapping those around makes no difference and I don't think it's a loose direction pin connection since both Z axis motors move the same direction, and it is completely consistent, not intermittent. That leads me to believe that it could be somewhere in the firmware, but I can't find anything that would do that. Does anyone have any ideas? I'm stumped here....

Firmware is unlikely to cause this unless you redefined your Z direction pin. The most likely cause is the direction pin. Since one driver runs both Z motors, this is consistent with the behaviour you describe. Grab a meter and check to see if the direction pin on the Z driver changes voltage as you issue up and down commands. If it isn't, then work your way back towards the processor checking for continuity.

The voltage isn't changing, and there's continuity all the way from pin 48 on the Mega's board to the dir pin on the driver board. Is there anything at all that could cause this that anyone knows of in the firmware, or should I consider that the arduino may have a hardware problem somewhere?

Edited 1 time(s). Last edit at 08/01/2012 08:26PM by smb1985.

Found it! There is a bad solder joint between the Mega's board and the Atmega 2560 chip. This may be hard to solder......

I'd look into having the Mega replaced. Reworking that solder joint would be tricky.

Alternatively, connect the Z-dir pin to an unused pin and re-define the pin in firmware to use that pin.