K-40 New Cohesion3D LaserBoard laser will not fire with software

Board: Cohesion3D LaserBoard
Firmware: _Smoothie
Software: Lightburn

Problem/ Question: _Did the board swap, Everything seems to work fine but the laser does not turn on. no burn no mark nothing. use the factory test button still fires just fine. while using the factory board and software works fine. change back to the Cohesion3D LaserBoard no laser. When I hit start it moves the head around just as if it was burning the image but nothing happens.
I am assuming it is a setting.
All wiring is factory swapped straight to new board.

Please provide pictures of your board, machine, and wiring.

Send some lines as explained here: PWM tuning for Smoothie Firmware such as the G1 X10 S0.8 F600

The head should move while firing. A red LED “Laser Fire Status” in the bottom left corner of the board should turn on.

Tell us exactly what does and does not happen.

1 Like

Ran all the codes as you suggested. It says ok the laser head moves around but never fires!

Unfortunately, like many of the Chinese machines, all the wires I was looking at are the same colour :joy: could you tell us which wires on coming from the LPSU are plugged in to:

That socket there?

If the commands are moving the head around on the laser I suspect that header is the culprit.

Also does the red LED mentioned above turn on when the laser is meant to fire?

2 posts were split to a new topic: New Board Not Firing Laser

Yes i believe the the light is red when it is supposed to fire. The one i circled in the picture correct?

Is the end of the connector which is marked in black pointed towards the same side as the sd card?

Yes it is

Let me just summarise this again to get this in my head.

It’s all working other than the laser firing?

X/Y movement, GLCD, LED for laser firing is lighting up.

Do you have a multimeter to test the cable you have unplugged in that last picture? The wire marked black and the blue one as well? I think it may just be a dodgy connection there.

Are these the readings you needed?
I have checked the connections. I have continuity both ways.

Hi William,

Let’s check a few more things.

If you remove the large power plug with the blue cables from the C3D, and touch the L (Laser Fire) to the Gnd signals within that plug (use a short section of random wire to do this), does the laser fire? I know you already said that you put the factory board back in and it is firing the laser, but I would like to verify this.

If that works, please make sure that when you put the blue cable power plug back into the board that the cables are fully pushed into the plug. They like to get loose and not make contact with the mating connector on the board.

If this still does not fire the laser, I can walk you through an alternate wiring configuration that we have available. It will simply involve connecting the Gnd and L (Laser Fire) wires to other connectors on the board, as we have 3 different mechanisms available on the board to tell the laser to fire.

Ground will go to the board ground which is available via the top left screw terminal right pin (indicated with black arrow), and laser fire would go to “FET -” which is the lowest screw terminal pin along the left edge (indicated with orange arrow).

Tried the tap with random wire Laser Fires. Replaced wires in screw terminals instead of connector still nothing happens with laser. Went to step 2 removed the wires from the plug for the C3D board and landed the ground (as indicated by the black arrow, then landed wire (L) under FET- as indicated by the Yellow wire. Results of when power turned on immediate and continuous laser fire.

Does this seem to be a bad board?

You ever get this figured out Tom?

Hi William,

Thanks for sending the board back. I’m not sure exactly what the issue was with the opto that fires the laser on your board - whether the component itself was bad, or it was just knocked loose, or it was a bad solder joint to begin with, but one side of legs was completely loose and not making contact with the pads on the board when I received it back and first inspected it. I have replaced that component entirely and your board is on the way back to you along with the other parts you ordered yesterday via USPS Priority.

​This is a pretty rare occurrence, but I’ll be looking at some additional tests the factory can run to further ​prevent these sorts of things from happening.


Ray Kholodovsky


BAD BOARD as i told him before 20 hrs of setting changes and trouble shooting. Then I had to pay for shipping back and didn’t get as much an apologize. To top it off he didn’t send me out a new board he soldered the old board and shipped it back out?!?!?

On another note it is up and running. going to install my Ztable and rotary this weekend.
I got them from this place. Randy has amazing tech-support.

Actually, he replaced the entire component before sending it back out rather than just soldering it. Glad it’s up and running again.

I think you are being a little hard on him though, he doesn’t have the same resources as those huge companies that can afford to overnight things, but he did still take care of you rather than letting you hang.

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