I have posted elsewhere about problems with the Z axis not torque locking. I have found that the Pololu 4998 driver chip has failed. The strange thing is that the Z axis can be driven up and down, and apparently behaves normally. BUT, the motors do not torque lock meaning that they can easily be turned by hand when powered up. Unlike the other axes which are rock solid under power.
I have proven it by swapping Z into Y terminals to see if Z behaves. It does with good strong torque lock.
I found the problem after noticing that the Z axis would not hold its reference position. I could also hear that the motors were not running properly. The carriage weight and friction are enought to overcome the motor torque.
So, what do I do? I would like to be able to graft in a new Pololu board to bypass the on board driver. The trouble is I have no idea how to do this, interms of the main controller board PCB connections and what goes where.
Link to the driver [
www.ebay.co.uk]
Does anyone have knowledge of this?