First CNC: frustration abounds

I purchased what was advertised as a 3040 cnc machine from Vevor. I’m getting a shock from my machine and controller box, so I disconnected all connections from the controller box, except for AC to the box itself and no longer get the shock from the machine but the box is still “live.” I contacted Vevor’s support and they suggested I look inside the box to check for a bare wire touching the case which I did and couldn’t find any wire(s) touching the box. They told me my machine was a “4030 Cnc Router Machine, Grbl Control Nema23 Motor” and offered me $190 (I paid $699 for the kit) refund but not a replacement controller box. I cannot locate a replacement box anywhere. A link to the machine I purchased is VEVOR CNC Router Machine, 3040 Engraver Milling Machine with Offline Controller Limit Switches Emergency-stop, DIY 3 Axes Cutting Kit for Wood Metal Acrylic MDF, 400 x 300 x 100 mm Large Working Area | VEVOR US

Any help to a link for a replacement will be greatly appreciated.Thanks.

If I were you I would find the source of the shock…shouldn’t be that hard to locate.


  1. What is your mains voltage?
  2. Have you checked the mains and verified it is wired correctly in the wall?
  3. What kind of shock are you getting? A mains type of shock or a tickle …
  4. Were on the machine did you get the shock? Point to the picture.

Post a picture(s) of the inside of the box and its wiring. Particular attention to the AC wiring



In addition to @donkjr’s questions, do you have a multimeter? If so, we can guide you through using it to test for — and almost certainly fix — an electrical fault.

If we find that it has the hot line (carrying your 120V line voltage) connected to the case, then it is dangerous and your credit card company may be able to help you, unless you are comfortable fixing it yourself, possibly using information we help you with.

Alternatively, we might learn that you have a mis-wired outlet in your house. Do you have an outlet tester that shows you about writing faults by illuminating lights to highlight correct vs. incorrect wiring?

Given the danger of shocks, I’d hesitate to ask you to do more testing by plugging it in. But did you already try plugging it into a different outlet?


This is the kind of outlet tester @mcdanlj refers to (assumes you are using US power):
Good tool to have around the house.


If you can open the control box and take a lot of pictures, that might help us troubleshoot the issue.

Hi, thank you for your reply. I will answer in order:

  1. The outlet is 110v
  2. I don’t have a socket tester but I will remedy that a bit later today
  3. The shock is a tickle
  4. the entire metal body of the machine gave the “tickle” as did the entire case of the control box
  5. I traced each wire to see if any of the shielding was bare and couldn’t find any that were; I will open the box again and take some pictures when I get home later today

Thank you for your reply. I do not own a multimeter. I will be getting a socket tester, per your suggestion, later today to test the socket. I will try a different socket today, as well.

Thanks for your reply. I will be opening the box again later today when I get home and I will take some pics.

How do I add pics here? I don’t see a button next to the emoji/soultion check/like/link or share this post buttons.

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That is the case: I live in the US.

You can drag and drop pictures or if you look at the bottom right when composing, if you’re using a smartphone, you will see and upload arrow.

I personally would not test it any further by touching it. But if you do, don’t do it barefoot, and do it without touching anything with your other hand. You don’t want current flowing through your heart.

If the outlet tests correctly, then we can help you use a continuity tester (one of the functions of a multimeter) to test which wires in the cord are connected to the case.

Without a multimeter, you could try testing it without touching it while it is plugged in. Plug it into a GFCI outlet (the kind with the “test”/“reset” buttons on the front) such as you likely have in a bathroom, kitchen, laundry room, or other wet space. If merely plugging it in trips the GFCI, then there is a dangerous wiring fault inside the unit. (A light or flag should show up if the GFCI “trips”, and it will typically make a “click” or “thunk” sound at the same time. If you aren’t sure what tripping a GFCI is like, press the “test” button and see what happens, but then press “reset” before doing this test.)

On your desktop web browser, you will see an upload button above where you write text. it’s right next to the bullet list icon. It looks like this:


I’m sure this is incredibly frustrating. I have good news: We can almost certainly help you find the fault, can likely help you repair it once we find it (or identify a part to replace) if you want, and also if you paid for this by credit card and the fault is in the unit, you should know that credit card consumer protection should be active; if they refuse to give you a complete refund in the case of us helping you confirm that the unit is faulty, you can initiate a dispute with your credit card company. (Obviously, on the other hand, if the fault is in your outlet, you’ll definitely want to fix that!)

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You could pick up a cheap (or free with coupon) multimeter from Harbor Freight. Also not a bad thing to have around.


Ahhhhhhhh! OK. I’ll get some pics up as soon as I can. Most likely Monday now. We had a bad storm here and a good portion of our tree fell onto our house, fence and neighbor’s house and I’ve been dealing with contractors, et al.

Just bought one from Amazon that will be here Monday.

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I bought one and tested the outlet, it shows an open ground - middle of three lights orange. I’ll have to get a GFI installed there.

As least it’s not a hot/neutral or hot/ground reverse!

The GFCI needs a ground to work.

Best of luck dealing with the storm damage! :grimacing:


I upgraded my little cnc to the same 500 watt spindle, looks the same.

I checked power supply (from past experience) before I plugged it in… between the power supply ground and the signal ground was about 50V…

I’m sure I would have lost smoke over that if I had plugged it in.

I’d suggest checking potential across the supply/board grounds after separating them.

Also between the supply and electrical neutral off the house mains.

If you are going to mess with this ‘low cost’ equipment, a multimeter is virtually a requirement. They are around $20 bucks for a cheap one… Suggest you invest … safely lets you see what you can’t see…

There are plenty of people that will help you learn how to use it, it’s not rocket science.

Good luck


Thanks for your response. I found an open ground at my outlet after I purchased a socket tester recommended by Donkjr.

Ok, after finding the outlet had a ground fault, I bought a band new GFI. after flipping the breaker, I pulled the outlet out of the box and installed the GFI. Once I had completed the installation, I plugged in the socket tester and flipped the breaker back on. VOILA! Two amber lights indicating it was working properly now, so I plugged in the controller box, set it it manual and tested the spindle. Boom! it worked.

I really appreciate all of the help you guys gave me. I feel a true sense of accomplishment. Now all I need to do is dig into GRBL and learn how to actually use my operational CNC.

Thanks again.


Yay! So glad to have helped. :tada:

Please do stick around, ask more questions as you learn, and also please feel free share what you make. :relaxed:

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