X axis error on a 325

[BugEyedValiant]

I have not run the mill for about 3 weeks and when I turned the machine on tonight the X axis started to shudder back and forth about .050 and when I opened the cabinet the x axis card had the red RMS indicator light was turned on. Where should I start for a diagnosis?

[elnerdo]

i had this problem once before myself (i have the servo dynamics amps). the problem ended up being the bias supply voltage to the drive was marginal. if you measure the voltage between pins 1 and 3 on connector J4 at your x-axis servo card and read something close to 28V you will likely be experiencing problems. its supposed to read 30V.

in my case, the voltage read 28.4 and the result was the x-axis behaved like you describe. the manual claims that less than 28V will cause the drive to simply shut down but 28.4 seemed to be marginal enough to cause problematic behavior. replacing the bias supply on the drive fixed the problem. the next time around i will likely be replacing the amps with something a bit more modern.

[BugEyedValiant]

i checked those pins and it had 11 volts. Then when I put the card back in the chassis one of the pins under the J4 connector hit what appears to me to be a SCR adjacent to it. Now none of the axis work, the green light is lit on the z and y cards but the o/c red light is lit on the x card. When I try to reference it, the display reads that the which ever axis you try to move has an error. I have no idea where to go from here.

[elnerdo]

are you saying the voltage measurement between pins 1 and 3 was only 11V, or was that one of the pins to ground?

when one of the axes in card rack fails to enable, it prevents the others from enabling as well because the enable signal gets is wired in series from card to card. so your non functiontinal x axis is likely preventing the other axes from being enabled .

you might want to check the fuse on the 15V power supply to see if it failed when the short occured, but from the likes of it, you are likely going to need have the card repaired. make sure to turn the power off to the machine when checking the fuse.

[BugEyedValiant]

pin 1 to pin 3 on J4 (connector nearest machine) was 11 volts. According to the card, the first pin is a -. I already checked the fuses and they are fine. I did not try to exchange positions of the x and y card to see if that would help. Are all three cards the same as I assume they are?

[elnerdo]

the three cards are the same but the tuning is different between the axes so you wouldn't want to swap them permanently unless your planning on retuning.

have you measured the voltage down at the +/-15V supply to see what it reads?

[BugEyedValiant]

I just switched the z and x cards to try and diagnose things, and still no servo movement on any axis. I did check the powersupply and they were +15 and -15.