K40 c3d board not activating laser in lightburn

Machine: k40, original board m2

Board: c3d replacement

Firmware: Smoothie

Problem/ Question:
With the c3d board installed, and everything wired up correctly (I assume), the laser does not activate in lightburn.

Lightburn recognizes the k40 smoothieboard c3d, and goes through the process as if it is burning, but the laser never activates. I have checked the 4 pin to L/G and when lightburn is going through the process, the laser activate light on the c3d does light up, as if it is attempting to activate the laser, but it does not burn.

The test button on top of the laser panel works, as well as the test button the LPSU works - if I press either of them while lightburn is attempting to burn, the laser DOES come on, but when I stop pressing it, it goes off. Meaning that the laser does function, the LPSU will activate the laser, and the c3d board is attempting to activate the laser, but it never actually fires.

I cannot upload pictures since new users cannot, but here are links to the pictures.

Picture 1 is the 4pin on the c3d board showing green for laser and white for ground
picture 2 is the 4pin on the LPSU that shows green going into L and white into G
picture 3 is the lights on the c3d showing 1/4 solid, 2/3 blinking so everything looks good
picture 4 is some of the rest of the wiring but showing the LPSU is green and will fire the laser when the test putton the LPSU is pressed. Same with the test laser button on the top of the panel.

Any help would be appreciated, as I cannot figure out why its not firing with the wiring correct.

Is there just some issue with the LPSU not connecting the 4 pin on the right side to the 6pin to the left of it? Could I bypass the 4pin on the right and put the board directly into the 6pin to its left? The documentation for this doesnt really help, as Ive been up and down the “knowledge base” and cant seem to find any information about why this isnt working…


You could connect the L and G of the power supply to a switch, to check if the inputs of the power supply are allright. If this works you can connect those wires to the laserboard. HERE you can find the right connection diagram for you power supply.

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