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Laser fires as soon as lid closed

I have a 100w yellow and black Chinese K40 style laser, and fitted the mg3 board around July of this year. I have been really happy with the board.

But today the red dot stopped working, and instead as soon as I close the lid, the laser fires and won’t turn off until I open the lid again. It’s almost like the red dot and laser have swapped places, except it needs the lid closed. Because I didn’t know what else to do, I disconnected the red dot, but it continues to fire the laser.

Does anyone have any idea as to what the problem could be? I live way way out in the sticks with no techs within cooee. I have attached photos of my mg3 connections and laser power supply connections.


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dancolwp1974 has reacted to this post.

Hi Glenda, I've looked at your description and puzzled over it.

The key thing to consider carefully is whether anything in the environment has changed. Did you get a software update affecting Lightburn for example?

Perhaps review the installation instruction video  to see if you've accidentally changed some settings in the software...

I can't see anything obviously wrong in the photos, am wondering if there's any dust around that could be causing a short circuit.

Also check that nothing has changed electrically. For example, are you using a different mains lead, or adapter board? Perhaps the earth connection is not solid, please see https://awesome.tech/k40-laser-grounding-instructions/

Sorry, this is really hard to remotely assess... From your separate email that indicated that the old controller doesn't work either, that points to the laser power supply. So you may need to make the leap of faith to buy a new one. I understand you're running a small business, so unfortunately equipment failure has to be accounted for as a cost of business.

In terms of local assistance, any trade that involves electronics may be of assistance. For example, a local TV repairman would have a good chance at locating the issue, and may or may not even be able to fix it.

Hope you figure it out soon!



Thanks for your reply. I think there might be a short circuit somewhere and am testing to try to find if this is the case.

I replaced the laser power supply in July when I replaced the laser tube, so I am hoping it isn’t that. But I am wondering if it is the smaller power supply that the red dot connects to?

As far as running a small business - I have purchased a new, larger laser, so I have a back up, so I am not totally shut down. I still like this laser and use it side by side with the other laser though.  I figure if the tube is still working the rest of it can be fixed.

I appreciate your help.

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