Dc servo motor control

Thanks Tommy, im still having some problems with the y axis (2 motors)

I set up the 2 home switches. I have y and y2 tandem motor, encoder and switches. Directions and encoders are good. I can start linuxcnc and home the y axis, it homes perfectly, squares the gantry and in the DRO is the home offset I set in pncconfig, but the Y axis jog keys are greyed out and cannot be used. Not really sure what can cause that.

You might need to press home all
If you have not got your other axes set up for homing yet, yo can set them to immediate homing as discussed in the homing configuration page in the main docs.

Tandem axis/joints/motors must have -1 in home_sequence, otherwise it will not jog. Even when set correctly, it will not jog before homing the machine.
So since the Y axis is moving and homing, set it to -1 and give it a try.
Just for kicks, set to to home slowly and set the offset of one side 2mm more, never gets old looking at that !
Yeah also very useful to make sure the sensor for y2 is actually y2!

Thanks tommy il get a play with the homing/squaring after some issues are fixed, Ive got going now, however i have a very noisy servo/drive on the rhs of the gantry, it was noisy before this retrofit started, the other side done similar before and i found a few bad solder joints, this one looks ok. Not sure what the cause os, brushes look good too. Had you seen any noisy ones before tommy? This has been a bit of an issue this past year, noisy and a small vibration

Noisy servo drive/m0otor almost always is due to bad brushes, be it the motor brushes or the tacho brushes.
It will also be caused by one or more burnt rotor windings or shorts in the commutator.
Check the corresponding drive, if it get noticeably hotter than the other drives, one of the above is the cause.
Failing to fix that will cause issues with tuning during normal use, namely even if the system is tuned properly, after a while the motor and the drive will heat so the tuning will shift, usually enough to cause following errors during fast moves.
Been there, done that.

Tommy i turned a small pot onside the drive 1/8 turn, now it is silent, still seems to work ok, but im not sure why this could be. 

On other notes, would you have any idea what polarity arc voltage is on the i/o cable for the thcad? I am confused because the work lead is positive on this machine. 

Maybe i will have to test first