Hi,
I don't have the manual for your drivers but guess that setting reduces the current to the stepper when it is stationary. It is a means of reducing the
heat build up in the stepper and a common strategy of driver manufacturers.

Craig

Hi,
it is the inputs to your A axis driver is sensitive to noise, not the outputs. Changing the output current to 3.2 or 3.5 amp will make it somewhat more powerful
'transmitter of noise' but wont change its input sensitivity.

Have you tried some ceramic capacitors on the input terminals?

Craig

Craig Hi,  Ceramic capacitors??  Nope, will have to go to the electronics house and see what they have... what capacity capacitor do I need?  I assume that these input wires are that ones labeled V+ and COM from the power supply.  Would I put the capacitor "inline" to the driver connectors?  Thank you for your half-current explanation.

bob

Hi Bob,
no, I mean the Step and Direction inputs, between the terminal and earth. Ceramic capacitors are commonly used in RF applications and are preferred in high frequency
situations but not mandatory.

Given that the capacitors are 'shorting' out the input then a large capacitor would stop the driver, not very helpful. A very small capacitor will present insufficient
load to high frequency interference and not work. Its a bit of a balancing act. I would recommend about 470pF. At that size they will almost certainly be ceramic.
Its highly probable that the driver has a capacitor of this description built in to its input circuit but may be insufficient or the manufacturer left it out to save that extra
few cents to make it for the price people are willing to pay.

Craig

Craig Hi,  thanks for the heads up... attached are a couple photos of the driver and one with the lid off... bob

sorry it would not import the other photo...

Hi,
just guessing, but suspect the upper left hand connector is the input and looks like two input buffers/Schmitt triggers or similar with little in the way of input signal
conditioning. I think a couple of capacitors are worth trying, I mean they're only cents apiece. As Rich has suggested do one thing at a time so that you can truly
evaluate each idea you've tried.

Craig

Ok Craig... thank you... will pick these up tomorrow if they have them.   bob

Craig I have tried 3 times to post photos to the forum but it rejects it each time.  If you will send me an email to me at anchorite@socal.rr.com  then I will send you the 2 photos I would like to talk about.  I need a picture drawn showing me how to do this ceramic thing.  can you send me a photo please?

bob

Gary, Gery, Craig, joeaverage, Chaoticone, and those others helping me, including the moderator and administrator.:   I did another experiment.  I swapped the supposedly malfunctioning drive from running the A-axis to running the X-axis.  I took the X-axis driver and put it on the A-axis.  So X and A have been swapped.   The stepper motor to the X-axis did the same crazy movement, growling sound as the A axis used to do.   The A-axis behaved beautifully, no problem at all.  I also went on the web and found youtube videos of higher end drivers malfunctioning... one guy bought 4 and 3 were bad.  So I am beginning to think I have a bad driver. Each time I do something, I go ahead and switch any non-shielded cable to a shielded cable.  bob