# Cnc Depot Spindle running strange **URL:** \ **Category:** General Chat\ **Created:** [April 13, 2026, 6:56pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018 "2026-04-13T18:56:20Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![TomMcAllister](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/tommcallister/32/4210_2.png) [@TomMcAllister](https://forum.avidcnc.com/u/TomMcAllister)\ **Post date:** [April 13, 2026, 6:56pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/1 "2026-04-13T18:56:20Z")
Hello guys. Has anyone had problems with their spindle rpm randomly oscillating? I used to have a mach4 and the 4hp hiteco. After I upgraded to CNC12 Acorn, i believe it may have started a minor oscillation problem. I don’t recall exactly. About a year ago or so I got my second hand but new in box rm40c setup. The rpm now varies quite a bit. Does anyone have any tips or insight for this? Thank you for your consideration. Here is a link to some video [https://youtube.com/shorts/kQvlLAxsK3I?si=FE\_ScgAVQZEkXu6r](https://youtube.com/shorts/kQvlLAxsK3I?si=FE_ScgAVQZEkXu6r) ---
**Author:** ![AussieMike](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/aussiemike/32/116_2.png) [@AussieMike](https://forum.avidcnc.com/u/AussieMike)\ **Post date:** [April 13, 2026, 10:01pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/2 "2026-04-13T22:01:06Z")
Hey Tom, I’d check the wiring between the controller and the VFD. It sounds like a loose connection to me. I use Masso, so not familiar with your controller, but if it controls speed with 0-10V, then measure the voltage at the VFD to see if it’s stable or bouncing. An analogue meter would be best, but you should still see instability with digital. If it’s stable, there’s something going on in the VFD. If it’s unstable, check the controller end. If that’s stable, the cable or connectors are suspect. If unstable, it’s likely the controller. Mike ---
**Author:** ![TomMcAllister](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/tommcallister/32/4210_2.png) [@TomMcAllister](https://forum.avidcnc.com/u/TomMcAllister)\ **Post date:** [April 14, 2026, 12:24am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/3 "2026-04-14T00:24:16Z")
I appreciate that advice. I will dig into the wiring diagram and see what I can meter out. I sent a message to cnc depot and they said it Is likely to be noise on that signal, and that I might need to add a capacitor to it. I’m not sure yet exactly how to wire that in, but I might try making sure the wire is moved away from the stepper wires and check inside the box and see if I can reroute it a bit to get it away from other wiring. Tom ---
**Author:** ![AussieMike](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/aussiemike/32/116_2.png) [@AussieMike](https://forum.avidcnc.com/u/AussieMike)\ **Post date:** [April 14, 2026, 12:41am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/4 "2026-04-14T00:41:49Z")
Yes, it could be noise. But why has it started now? Let us know what you find. Mike ---
**Author:** ![TomMcAllister](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/tommcallister/32/4210_2.png) [@TomMcAllister](https://forum.avidcnc.com/u/TomMcAllister)\ **Post date:** [April 14, 2026, 1:05am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/5 "2026-04-14T01:05:53Z")
Well I don’t run the machine all the time. It has definitely always done it since I got the new spindle, but seems like it’s been getting worse. Recently. The machine sits for periods of several weeks to maybe even a month or so between projects. I am a remodeler and make cabinets with it here and there. Then occasionally use it to make something fun. I will definitely follow up here when I get it resolved. If anyone else has any input, I’m all ears. Tom ---
**Author:** ![MichaelR](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@MichaelR](https://forum.avidcnc.com/u/MichaelR)\ **Post date:** [April 14, 2026, 1:37am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/6 "2026-04-14T01:37:08Z")
Avid has mentioned they started adding a capacitor between the pins that provide the voltage to the vfd to address rpm stability. Eric will probably be by to add his 2c but I think if you talk to support they will get you what you need. > [@AV40S speed oscillation](https://forum.avidcnc.com/t/av40s-speed-oscillation/5557): > > I got an AV40S spindle a while back and this week I did a little milling with a 2.5” slab slayer bit. I noticed during the spindle warmup and then during use that around 16k rpm the speed oscillates pretty noticibly. I have never seen this with a bit that doesn’t have a lot of angular momentum like this one. I’m not too concerned, just wondering if others have seen this, or I have something to look into here. I am also using the old VFD that came with my original 3hp spindle, but the 3hp and… ---
**Author:** ![jjneeb](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/jjneeb/32/244_2.png) [@jjneeb](https://forum.avidcnc.com/u/jjneeb)\ **Post date:** [April 14, 2026, 2:32am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/7 "2026-04-14T02:32:00Z")
Yep, that solved it for me. They sent me the cap, and it just screws on the spindler analog connector. ---
**Author:** ![TomMcAllister](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/tommcallister/32/4210_2.png) [@TomMcAllister](https://forum.avidcnc.com/u/TomMcAllister)\ **Post date:** [April 14, 2026, 2:43am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/8 "2026-04-14T02:43:00Z")
I’ll check in with them tomorrow. Thank you Jim. Tom ---
**Author:** ![Eric](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/eric/32/3220_2.png) [@Eric](https://forum.avidcnc.com/u/Eric)\ **Post date:** [April 14, 2026, 11:40am UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/9 "2026-04-14T11:40:18Z")
You’re on a third party spindle and VFD right Tom? If that’s the case your mileage may vary, but you can try a 1uf capacitor to start across the 0-10 volt pins on your Acorn. You can get a pack of the like this: [ALLECIN 24 Values Monolithic Ceramic Capacitor Assortment Kit 10pF 20pF 30pF 47pF 56pF 68pF 100pF 220pF 330pF 680pF 1nF 4.7nF 10nF 47nF 100nF 0.15uF 0.22uF 0.33uF 0.47uF 0.68uF 1uF 2.2uF 4.7uF 10uF: Amazon.com: Industrial & Scientific](https://www.amazon.com/ALLECIN-Monolithic-Ceramic-Capacitor-Kit/dp/B0C1V8Q93P?sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY) Make sure they’re non polar, if they’re polar MAKE SURE you get the polarity right or you’ll let the magic smoke that powers all electronics out. ---
**Author:** ![TomMcAllister](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/tommcallister/32/4210_2.png) [@TomMcAllister](https://forum.avidcnc.com/u/TomMcAllister)\ **Post date:** [April 14, 2026, 3:45pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/10 "2026-04-14T15:45:11Z")
Eric, thanks, I ordered a similar kit that will get delivered today. I appreciate all your guy’s help. I will update later after I install the cap. ---
**Author:** ![djdelorie](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/djdelorie/32/515_2.png) [@djdelorie](https://forum.avidcnc.com/u/djdelorie)\ **Post date:** [April 14, 2026, 3:56pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/11 "2026-04-14T15:56:52Z")
These kinds of reports make me glad I put in the effort to switch my setup (linuxcnc) to modbus spindle control. Is that an option for the Avid setup? For me it was just a usb adapter and some software config… ---
**Author:** ![JeffsDesign](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/jeffsdesign/32/5574_2.png) [@JeffsDesign](https://forum.avidcnc.com/u/JeffsDesign)\ **Post date:** [April 14, 2026, 4:14pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/12 "2026-04-14T16:14:57Z")
Earlier you talked about moving the wires but aren’t these wires shielde? ---
**Author:** ![Eric](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/eric/32/3220_2.png) [@Eric](https://forum.avidcnc.com/u/Eric)\ **Post date:** [April 14, 2026, 4:23pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/13 "2026-04-14T16:23:42Z")
> [@djdelorie](#): > > These kinds of reports make me glad I put in the effort to switch my setup (linuxcnc) to modbus spindle control. Is that an option for the Avid setup? For me it was just a usb adapter and some software config… No modbus here, at least not natively. In my (limited) experience with Modbus it can be very persnickety… For us the 0-10 is dead simple, works with nearly every VFD, and is mostly error free. Every modbus VFD i’ve used has been a PITA. For us that’s a massive support headache. ---
**Author:** ![djdelorie](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/djdelorie/32/515_2.png) [@djdelorie](https://forum.avidcnc.com/u/djdelorie)\ **Post date:** [April 14, 2026, 5:01pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/14 "2026-04-14T17:01:10Z")
I figured as much, my setup took some work. But, your “dead simple” seems to have some gotchas, and you know which VFDs you’re selling… 😉 ---
**Author:** ![Eric](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/eric/32/3220_2.png) [@Eric](https://forum.avidcnc.com/u/Eric)\ **Post date:** [April 14, 2026, 6:42pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/15 "2026-04-14T18:42:12Z")
> [@djdelorie](#): > > and you know which VFDs you’re selling Not necessarily… we move a lot of them and have had to change from time to time ---
**Author:** ![TomMcAllister](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/tommcallister/32/4210_2.png) [@TomMcAllister](https://forum.avidcnc.com/u/TomMcAllister)\ **Post date:** [April 15, 2026, 1:32pm UTC](https://forum.avidcnc.com/t/cnc-depot-spindle-running-strange/6018/16 "2026-04-15T13:32:34Z")
Ok I slipped a 1uf ceramic capacitor in between the 0-10v speed and analog common terminals on my vfd. Problem solved. She’s running smoothly now. Thanks so much guys! ![IMG_5359](https://canada1.discourse-cdn.com/flex027/uploads/avidcnc/original/2X/5/5791bde9edac8d4b67ba7ee000b118416879ae8b.jpeg)