C3d Mini, laser not firing

Machine: K40

Board: C3D mini

Firmware: _Smoothie?

Problem/ Question: i have installed the mini according to the instructions but laser wont fire.
It had a 4 pin connector for the laser and i connected the laser wires to the fet terminals with no luck, didnt matter which way i put them
Test fire button fires as it should
This is my original board

Hi Jesse,

Welcome to the forum! I have upgraded your trust level so that you can now upload photos.

Please provide clear pictures of your machine, control panel, board, other electrical components, and wiring with the Mini connected. We need to see how and where everything is connected.

No worries, will do when im home in a week hopefully.
Thanks for the reply

Hi Jesse,

Thank you for the photos. Where is the power connector for your laser?


What are the two black wires you are holding and what do they lead to?

Can you also provide a photo of your laser power supply unit, so I can see the connections at the LPSU end?

Power is going into the blue screw terminals.
The black wires are my laser and ground that need to be attached to the FET
Is the laswr power supply not the first photo?
The black wires go to the bottom between the 4 colour plug and the 2 white wires

Hi Jesse,

Thanks for following up.

You mentioned the original board had a 4 pin connector for the laser. This is what I was referring to when asking about the power connector not being connected to the board.


Looking at the pins on your original board, it looks like you had a 3 pin and 2 pin connector. Do you still have the original 3 pin connector saved?


To make sure we’re referring to the same thing, this is the connection for the C3D controller PSU (power brick), wired to the screw terminals on the Main Power In (see the top red box in the image below).

Do you have a separate 24V power supply connected there? You can see an example wiring here: Mini Upgrade Kit


The Laser and G connect to the respective K40 PWR Laser Fire and GND pins (see the second and third red boxes in the image above).

If you have a separate 24V power supply connected as previously mentioned, then you do not want to connect the 24V wire to the power pins and you can use shrink wrap or electrical tape protect it, since it will be unused.

If you cannot use your original power connector to attach to the top 3 power pins, you will need to source a female JST VH 4-pin latching connector to hook up there. The standard that comes on most K40s is 3.96mm Pitch, and you can see there are a couple of variations of style from the one in our installation instructions to the type I have below:

Ah, thank you… Congratulations, you win the prize for oldest LPSU I’ve seen to date! :slight_smile:

Are there any labels on the LPSU board to indicate pin designations? Make sure to trace the matching wires from there when wiring into the power connector.

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