Fadal 4020 Electrical Filter (for lack of better terms)

Can someone tell me what these devices are? I cannot locate them in the parts book and fadalcnc.com says they are no longer available but also couldn't tell me what they are. One of ours gets hot to the touch and makes an audible buzzing noise before faulting out the machine. This only happens when our 4th axis is plugged in. It seems like as soon as we plug the 4th axis in it's trying to turn slightly which overloads this filter or whatever you want to call it. We've sent the 4th axis motor out and had it rebuilt and tested on a different machine and apparently it checked out. Fadalcnc did not send any sort of paperwork back with the motor and any calls to them result in no sort of records in regards to our motor rebuild. Kind of shady but it is what it is at this point. We've swapped amp boards every which direction end ran tuning programs on them. Machine runs fine until the 4th axis is plugged in. The 4th axis doesn't even have to be turned on in the control. All we do is, while the machine is powered off, plug the 4th axis in and after 10 seconds the audible buzzing sound starts and it faults out. It will fault out any axis it chooses. If we go to the CNC cabinet and trip the reset it's fine for about 5 seconds before the audible buzzing starts and it faults out again. The 4th axis did work when we first got the machine but the more we used it the more it would start to fault out. I'd just like to know what those devices are so that I can try to source one. If we continue to have problems after that we will address them later. We've done so much troubleshooting we are at the point where we'd like to address that filter first as it clearly should not be doing that. We had our electrician ohm out every single wire in the 4th axis pigtail and they ohm out fine. All of the plugs appear to be in good shape as well. About the only thing we haven't done is cut the wires to 2 of these filters and swap them to see if it moves to a different axis. We were trying to source one first before having to cut wires twice. Any help would be appreciated. Please let me know if any other details are needed. We have a 4020 from 1995 and we use format 2 if that matters any.
Thanks,
Crosscut Solutions Inc
Manawa, WI

I can say that the Add-On 4th axis kit does not use these filters, and the Motor wires go directly to the cannon plug on top of the machine.
I only see the filters on the DC 4 amps chassis, and not when using the add-on chassis for the 4th/ 5th axis.

So is it really needed for the 4th axis or not, I don't know?

So on the built in chassis, if I remember correctly (double check), the wiring comes off the AMP from MTR+ and MTR- which should be terminals 3&4 (Terminals 1 & 2 are power and ground), then those two wires go thru the transformer or filter, then go to the right side of the chassis to the terminal blocks #7 and #8 which goes to the A-Axis motor. Double check that, but it seems it would be pretty easy to just bypass the filter to see if it really is the problem.

https://www.cnczone.com/forums/attac...d=427204&stc=1

Would this be L201 in the attached picture?
Section 6 of the Maintenance manual has a little info on it. Basically, the manuals have tub loads of info on the AC Brushless stuff, but not a lot on the DC chassis. On the AC, they even provide part numbers, but not on the DC version. It's like they missed a few pages.

rwskinner - Thank you for the replies. That is interesting to know that when the 4th axis was added on after the fact these "filters" were not used and it makes you wonder if they are needed. It also appears that your schematic is correct although I haven't traced the 2 wires all the way over that come out of L201. At this point I think it's worth our time to try and bypass the one that is making a screeching noise just to see what we end up with. I'm wondering what would be worst case if that "filter" is really needed. I'm assuming we could possibly cause harm to the 4th axis motor and hopefully not to the amp board or controller board. I will report back with our findings next week. Thanks again.

Any luck?

Not yet. Our electrician hasn't been in yet to try it and I'd much rather have him do this than myself or our operator if you know what I mean. I will post our findings on here.

Well we FINALLY had a chance to bypass this filter thing. After plugging in the 4th axis and powering up the machine there is no audible buzz anymore! Clearly that noise is coming from that filter thing. BUT after we turn on the 4th axis in the control and reboot the machine we get a fault that reads "A axis fault as follows: Motor Overload." This is very unfortunate since Fadalcnc.com supposedly went through this motor and rebuilt it. Maybe it's not the motor but I have yet to hit up google. After we got the fault we ohmed everything out and continuity is still good so I don't believe any wires melted or anything of the sort in the motor. The one thing we did notice was that once the fault appeared on the screen, the red fault light on the card is extremely bright. I'm thinking those filters must reduce voltage to some extent but that's neither here nor there at this point. Any suggestions??

Id put the filter back in to start since that didnt cause your problem. The fact that the filter was buzzing confirms there is an overload, and problem is most likely downstream from there. Id doubt its a bad amplifier, but ya never know. You checked the resistance at pigtail, try checking it right at the point of where you unplugged the filter. Maybe theres are broken wire somewhere else in the harness or connector. Also check for a short to ground.

You just had the motor rebuilt, is there a chance you installed it wrong? Something binding? Is the brake stuck on? DC motors are pretty simple to test. Seems very unlikely that they would rebuild it and send it out completely dead.

The current is going somewhere. If theres no motion it pretty much has to be something binding, something shorted or dead motor.