Sculpfun S9 Laser power declining after a few minutes

Hi all. Just wanted to pick a few brains here. I have a Sculfun S9 now for a year and everything has been working great up till a few days ago when I started noticing a sudden decline in the power emitted by the laser. I started a job and 90% of the cuts went through however the last few lines never cut all the way through.

I then started another file and I could visually see that the light emitted was duller than before. I did some more tests and it got to the stage where no light was being emitted at all. I checked all my cables were good, however when I opened up the fan above the assembly I saw a dry joint on the positive wire, I resoldered and the fan was completely dead, not spinning at all.

My question is how much does the fan influence the working of the diode, I know the fan is meant to keep the housing cool, but if the fan stops working can it have the effect I am experiencing where the laser gets too hot and has a “burn out”

I have ordered another fan, which i am still waiting on, but was curious in the meantime to see what everyone thinks the impact a broken fan could have on the diode.

I have not found an effective way to tell if the diode in a module is dead or if the surrounding electronics are at fault.

From your symptoms, it sounds like the diode has failed, probably from a bad fan or its connection.

Stable power and adequate cooling are a necessity for reliable laser diode operation.

Replacing the fan is a good idea since it is inexpensive to try.
I would also check the power going to the laser diode module and insure it is stable at the correct value…


Hi Don.

Update. Thanks for your input. The new fan arrived and I connected it up and this new one is powered up and running. Did a few test cuts and perfect, cutting even better than it was before. The real test is currently on the go, running an engraving picture file on a black slate tile and so far so good. It would seem that the fan was indeed having a major impact on the laser output. Just a pity there is no warning when a fan is busy “checking out” Could have save me a great deal of anguish.

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It would seem that the module has some temperature protection which is surprising and impressive.

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Dammit, I spoke too soon. After 20 odd minutes the laser lost power again. So safe to say that the fan only has minimal impact on the diode. Looks more like the diode itself is on the way out. Interestingly I see the light being emitted looks like it is shimmering and not as solid as before which might also indicate a diode is busy failing.
Ah well, it would seem like an new module is the answer in this case.

Heat does kill LEDs, including the laser kind. It’s why high-power LED light bulbs die quickly, too.

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Seems to kill about everything … not only circuits …


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I would say this sounds a bit like the driver is dying.


I agree with @donkjr , if you /can/ get a full power beam but this fades after time then I dont think the diode is failing, diode heat damage is permanent.

But if your controller has a thermal protection circuit and the diode is not adequately cooled this would explain your symptoms nicely.

Alternately, the driver module for the diode may be overheating and shutting down as a result. Most use generic dc-dc converters (basically they are current-limited buck converters). The controllers for these usually have some over power and current protection circuitry inbuilt.

How hot does the controller board itself get? can you cool it? etc… maybe test with a second small fan helping the board.

Also; if your workshop/enclosure gets hot it may be worth looking at ambient temperature since cooling fans get less effective as the ambient air gets warmer.