SOLVED: Compact 5 CNC Feed Speed slow in Hand mode


I got it sorted!  This 10K pot was the problem. I didn't notice it until I pulled the board out. It is in series with the main pot and is used to calibrate the actual feed speed to match the dial on the panel.
This 10K ohm pot was testing at 500K ohm in the center of its sweep.  This caused the Resistor/Capacitor circuit for the 555 to be super slow.  Surprisingly the computer still accepted the delayed pulse rate and ran the axis at roughly a tenth of the normal speed.

It is adjustable from the back of the board through this hole. 

I actually managed to find a 10K pot on hand I could make fit. 

The drives/axis still have a bit of a pulse that I didn't notice while running in CNC mode.  That may require further testing but for now I am happy to be back up to speed.

Thanks for the help JG.


No problem - glad it is fixed.
I forgot about the trimpot :-(

What is the "pulse" issue ?


Not sure what the noise is, but there seems to be a surge/pulse that matches the speed of the axis.  My first guess is it is a hardware issue.  This thing hasn't been moved or lubricated in at least a decade. My other guess was there might be a slight interrupt in the drives as it updates the DRO.  I'll have to check and see if it is present in CNC mode. Any ways, I made the first cuts with it today and it doesn't seem to effect the cut quality. 



- The drives/axis still have a bit of a pulse that I didn't notice while running in CNC mode

All C5 makes the same noise in MAN mode when moving fast, the CPU is to slow to keep up
and the small delay when computing the steps creates this awful noise.(it's interrupt driven )
The original stepper motors have a very low inertia so they have no problems with loosing steps.
Reduce gradually the speed with the pot and the noise disappears.

I installed new motors ( in fact old hybrid steppers rewired and new rotors to change them into reluctance steppers)
to have 200 steps/rev, but they cannot tolerate the delays and loose steps, so I needed to reduce the max. velocity with the trimmer.


Of course you need to lubricate the spindles and the slides immediately, don't use the C5 anymore before that done..
I didn't care and had after problems with the X-axis.