Laser Can't Fire Below 20% - but it used to!

Hello everybody. I’ve tried to find a specific answer to this question in the existing forum entries, but couldn’t come up with one. So here’s the situation:

Last time I fired up my laser was about 8 months ago. We moved and just haven’t had time to use it. The new climate is MUCH colder than our old one - not sure if this contributes to the situation, but figured I would include it just in case. Laser seems to be in good order. Everything turns on and initial test burns of my tried and true test file were good.

The problem started when I began attempting to burn some more delicate designs that my wife had been working on. I found that my laser simply won’t fire on any layer with a power setting below 20%. Actually, it will start to fire on settings as low as 15%…but then it cuts off and I have to turn the laser off and then back on to get it to fire again. But with settings at 20% or higher, it’s like old times. No problems.

I have definitely burned as low as 10% in the past. Nothing has changed with the laser, its setup or its settings. I literally moved it from one place to another. Then waited a few months before turning it back on.

The only notable difference, as mentioned above, is the temperature. For example, my ‘chiller’ used to run at about 30 degrees celcius…but here in the new location it is running at about 20 degrees celcius.

I did notice that on the main screen of my Ruida controller it says MAX POWER: 50%. The thing is, though, that I had never really noticed that before, because I wasn’t looking at it before. But while reading some other threads it was mentioned, so I took a look. I also saw some people discuss manufacturer min/max settings, but I don’t have the password to access those…so I’m certain that I haven’t changed them :smiley: With that said, as soon as a file starts from Lightburn that MAX POWER settings changes to whatever the file is set to in Lightburn.

Also, I have tried running files over USB, but have also sent files to the machine and stored them there to test with as a way to make sure the problems isn’t related to the connection.

Has anyone else had this issue? Any ideas on how to resolve? Please advise.

Thanks in advance!

Ruida 6445 Controller
Reci w2 80w/90w Tube

The tube is older and has been used. As a tube ages/used it’s chemistry starts to break down the gases so it takes a higher energy level to lase.

I’m running mine ‘warm’ at 25 C … you are running 86 F, I think is too warm. The recommended temperature seems to be about 20 C or 68 F.

Mine lases at a lower percentage when at a lower temperature. The lower temperature also extents tube life, they claim.

Tubes are ‘consumables’… it may be that time…

Good luck


Thanks. I’ll take this into consideration. In total, I’ve got about 40 hours on the tube which doesn’t seem like a lot, but perhaps that is the issue. As for the chiller, now that I’m running lower - 20c instead of 30c - I would have expected the laser to become more efficient, as you suggested…but no luck.

If you toasted it at 30 C, maybe it’s too late … ? I don’t know but the larger the laser the higher the minimum lase percentage seems to be.

The only other thing is the optics and focus…


Definitely something to consider, though when I was ‘toasting’ it, the performance was much better and more reliable.

Regarding optics and focus, how would that influence the power level at which the device can successfully lase/fire?

Maybe the performance was sub standard… how would you know?

I think it’s well know that higher operational temperatures shorten tube life…

Optics get dirty/reflectivity can drop, so the optical path is always in question. What makes a laser work is the lens… any problems there and you will see it.

I’m just advising you to double check, that’s all. A wattmeter is useful here, do you have any such animal?


Perhaps it was substandard compared to whatever ‘perfection’ might be…but compared to what’s happening now, it was much better. I burned well over 100 projects with varying levels of detail and never once had the laser fail to fire or cut off after initial ignition. So, sure, it most likely wasn’t ideal operating conditions…but at least it was operating.

Are there any specific tests to check the health of the tube itself? Like gas concentration, ignition point, etc? Replacing a tube with less than 50 hours on it seems drastic if there might be other ways to sort this out.

The ‘Max Power’ setting shown on the controller screen doesn’t affect things the way you think it does. That value, and the Min Power setting on the controller panel, are only used if you enable ‘Use Default’ in LightBurn - those are the defaults.

Most likely your tube is aging, and if you were running at high temps before (over 30c can damage the tube, so if you were close to that, you might’ve reduced the tube life a little).

Glass tubes also have an ‘ionization point’, below which they won’t fire, and that is affected by ambient temperature and tube life as well. It’s possible that point is higher now than it was in the warmer climate.

The problem with ‘checking’ a tube in any of these ways, is it’s more expensive than a new tube. To get to the ‘gas’ you have to ‘break’ it’s seal. Before it put back into operation this has to be ‘patched’. Even if you could get the gas sample what would it cost to have it analyzed and after that you end up replacing it anyway.

There is no ‘ignition’ point, I assume you’re speaking about when it ‘lases’. This again varies with the tube… Even tubes identically manufactured will vary.

The only way to really tell is to measure the output of the tube. Of course you have to have done it previously to know if a change has occurred.

I do agree with you that 50 hours on a tube is very disappointing.

You can check the resonance of the tube or how it’s lasing, but I doubt you will find anything doing that … it just sounds like it’s going bad.

Here’s a link for TEM states if you wish to look at it…

Might take a few and watch this video from Sadler … his video explains purchasing lower grade tubes by well know manufacturers.

Good luck… let us know how it works out…


Btw, a new development which might hold the answer: My CW3000 Water Chiller fully died yesterday.

Basically, it comes on, lights up green, no alarms…but the pump/fan do not turn on anymore.

I’ve ordered a new CW5200 to replace it, which will arrive next Thursday. But I am now wondering if possibly the water flow was inadequate recently as the machine was in the process of failing. The water flow alarm never came on at the laser or at the chiller, and even now the alarm doesn’t come on for the chiller. I’m not going to turn the laser on again until I get the replacement chiller. I did check that water was flowing through the hoses, and did the ‘pinch test’ to make sure the alarm sounded previously…and everything seemed to be in order…but perhaps the flow was just enough to keep the alarms from triggering, but not enough to actually cool the tube.

I’ll update again after I get the new water chiller installed and tested.

Thanks again to everyone for their feedback.

Do you have your coolant alarms wired to the lasers lps or does the controller you have handle that?