# Did I fry my Ender 3 V2 Main Board?

I was replacing the nozzle on my E3D V6 clone and the hotend started turning so I held onto it with pliers while I tightened it.

As I did this, the positive wire of the fan that clips onto the E3D V6 melted on the hotend and threw a spark. At this point, the extruder started running so I hit the power switch then unplugged the main cord.

I checked everything to see what caused it, then turned it back on once I figured out what happened and made sure everything was good. Now when it's powered on, it seems like it's still getting power; the BLTouch turns on but the screen doesn't show anything just the backlighting.

Did I fry my board?

• The first warning on printer controller boards is to never unplug stepper cables when powered. Please look at Why does (dis)connecting a stepper motor while powered on damage the driver?.
– 0scar
Jun 6 at 21:56
• I actually ment the main power cord, not the extruder motor. I also hit the off switch then pulled the cord. Sorry for the confusion, I'll edit that.
– D187
Jun 7 at 0:10
• If the new board arrives, please post an answer that you replaced the board and report if it works. You can even accept your own answer after 48 hours. If not, update the question. Please check all hardware before you connect it to the new board to prevent damage to the new one.
– 0scar
Jun 7 at 11:49
• Ok I will. I think I actually missed the cutoff to get it today. When I was ordering it there was a few seconds left to be able to get it next day and I was literally like a second late. I checked the email and it said I'd receive it by Tuesday. I dont see why they wouldn't ship it for being a second late if they had other orders to send out though.
– D187
Jun 7 at 12:07
• Question marks are not a problem. You need to replace the thermistor.
– 0scar
Jun 8 at 22:36

Yes, you can damage stepper drivers when you unplug stepper motors. Hot (un)plugging of stepper cables can cause voltage spikes that can destroy the stepper drivers. Furthermore, shorting out the fan may have caused damage also to other parts of the board (voltage regulator, fuse, etc ). These controller boards are not that expensive, ordering a spare would get you up and running quickly. Also order a new fan, mind the voltage.

No, pulling the power cord or switching off the controller board will not destroy the board.

• Yea I ended up just ordering one on Amazon so I could have it by tomorrow. The fan actually still comes on when I turn the printer on. I think I must have clipped the fan upside down onto the E3D V6, I cant imagine that the fan wires should be that close to the hot end. Not sure why I didn't catch that when putting everything together in the Bullseye Mod. Thanks for responding. Note, I actually turned it off before unplugging it so I didn't really hot unplug it. I would have thought the fuse should of blown from a short instead of the board
– D187
Jun 6 at 22:16
• A basic rule of electronics going back at least to the early transistor era (1950s): a $2 transistor will protect a 3 cent fuse by blowing first. Jun 7 at 11:12 • Can you point me in the right direction to info on doing this? Or was this a joke? Considering its costing$2 to protect a 3 cent fuse.
– D187
Jun 7 at 11:16
• I think the comment was meant to be informative, it gives some insight in the choices made in electronics design, not always the good ones. You frequently see components fail where the fuse didn't, hence the comment I think. It is difficult to find the problem, it can also be a burned trace, SMD fuse, MOSFET, etc. Hard to find and hard to fix if you're not an electronics engineer with soldering skills.
– 0scar
Jun 7 at 11:44
• Yea I realized what he ment after I replied lol.
– D187
Jun 7 at 11:50