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No laser power

Hey guys,

I'm helping a buddy set up his k40. He bought the exact same one as me so I suggested he get a mini grbl right off the bat. We installed the mini grbl exactly like I have on mine and having a problem.

We got it to connect to lightburn no problem. The problem is, when we send a file down to be engraved, it moves into position and starts, but the laser never fires. When we cancel it and send it home the led2 turns a solid red with no blinking. To turn it off I either restart lightburn or select a different com and reselect the right com.

I'm not sure its a board problem but thought I would check here since the constant red light might indicate something. I checked the troubleshooting diagram and there wasnt a bubble option for constant red light on led2.


His settings are the same as mine:










(ATC M6, pulse/ff)


(ATC Tool Td, milliseconds)


(ATC M6 Td, milliseconds)






(Softstart, milliseconds)










(Spindle freq. 0 to 15)



































(x:mm max)


(y:mm max)


(z:mm max)


(a:mm max)


(b:mm max)

Hi In order for the laser to fire, the following connections on the power supply needs to be grounded: LP and WP. The LO signal is controlled by the Mini Gerbil.

Best way to check is with a cheap multi meter (V DC setting).


Cheers, Paul

Cheers, Paul awesome.tech

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