Cannot adjust power on K40 with replaced motherboard

Hey Guys,

First time poster. I have a lower end K40 that I have been using for some time. Mostly, I cut/engrave on paper, cardstock, and thin wood (1/32", 1/64," 1/16"). I work with scale miniatures (1/12th, 1/48th, 1/144th). I create things like doilies, putz houses, plant leaves, and tiny furniture. Previously, I have used K40 Whisper to accomplish this. Each switch from engraving to cutting had to be manual.

Recently, I have acquired a Monport motherboard and Lightburn. I am so excited to finally be able to change speed and power without having to stand at the machine to switch power and speed when needed. After replacing the old with the new Monport motherboard, I am unable to adjust the power. I can adjust the speed, just not the power. Power seems to be on full throttle the whole time. I am not very technically minded and do not understand much of the ins and outs of the machine. I would truly appreciate any help you can give to help me accomplish my goal. Thanks so much…in advance.

I am attempting to attach pictures.


There are two ways to control a K40.

The original design uses a operator controlled pot to adjust the IN voltage to the laser power supply (lps). PWM turns the laser on/off at it’s set level of current.

Monport has started to bypass the manual pot and run the PWM directly to the IN terminal of the lps.

Do you know how yours is wired? Do you still have an operational pot for the operator?

:smiley_cat: