Is this the result of a dying laser tube?

Hi Everyone,
I have been away for about 3 weeks, before I left my laser was working fine although perhaps with a decline in power output. The laser has been sitting unused during that time, and when I got back today, it was not working properly. I tried a raster engraving and it appears to only engrave the edges of the letters, like it fires but quickly loses power after about 2mm and then after it is turned off and on again by the controller it works again briefly but then fades rapidly. (see attached images). Am I looking at a failing tube or is it more likely to be something else?

Do a good look to check the mechanics are ok then you have to check alignment/optics.

You need to ensure it’s not one of the previous issues, mechanics or optics. I’d suggest you start at m1 and go through the machine.

Since it’s a relatively acute failure, it doesn’t sound like a tube to me. More like an lps. If it’s been slowly failing, then an increased probability it’s the tube.

Do you have a mA meter to see what kind of current it’s running?

Ensure that it’s running in TEM0 resonance. You check it at m1, where the beam comes out of the tube… should be first step in alignment, m1…

Good luck


Looks like an alignment problem.

Doesn’t look focused. If this is as good as you can do then test fire into wood just off the tube and post an image of the burn pattern.

Thanks everyone for your replies.

I went back and rechecked the alignment and focus, everything looks correct.

Here is an image of the test at the first mirror, right out of the laser tube. Does this mean that the tube has a mode failure? The power output seems a lot lower, usually a instantaneous pulse leaves a solid burn mark, while realigning this time I had to hold the button down for a second or so to get a decent mark.

Further update, I tried a test with a lower power and at lower speed just to see what happened, and it seems to work a lot better at the lower power setting.
Could this mean it’s a power supply issue?

80% power, 300mm/s

40% power, 150mm/s

I think your tube is history… sorry.


I would figure out what happened so you don’t damage the next tube.

OK, do we think that a failing power supply could cause this? I might get another power supply anyway as a backup, also as they are significantly cheaper than the laser tube. Can’t think what else could’ve caused it.

Thanks all for the assistance.

Check your mirrors too. I noticed a gradual decline in power and quality. The mirror on the laser was degraded.

New mirror, eeryting back to normal.

No… I’ve never see this problem resolved by another lps.


1 Like

Did a power supply cause the tube to fail? Might have if it overpowered the tube. But that’s a pretty large tube to overpower. Could be a defective tube. How old was it? Could have run out of water? Temps got too high during the previous session? This tube needs a compressor style chiller.
Replacing marginal components with quality components is a good thing.

1 Like

Yes, I meant to ask could a faulty power supply damage a tube in this fashion, not whether replacing the power supply would fix the tube.

The tube was about 2.5 years old, it is a RECI W6 130W (genuine according to the QR code), it possible I could have overpowered it, I have noted the power supply was for 150W, the max I have run the duty cycle at was 98%, usually 80% or lower however. If my calculations are correct, a 150W power supply can put out 35mA current at 100%, and the W6 tube is 28mA max, 26mA recommended, so I should have been running max 80% or 74% normally, is that correct? Or does the tube only draw what it needs?

I’ve checked the water flow, it was still good, the laser was supplied with a CW5200-style chiller. (I don’t think it’s a ‘genuine’ one, they seem to be very commonly counterfeited to the point where it is basically a generic model number).

I’m thinking to replace with an 75W or 90W RECI tube and matching power suppply, does anyone have any recommendations. How do we feel about W vs T series RECIs? Any better glass tube brand?


All looks correct. What temperature were you running? Don’t know anything about Reci. Lots of fakes I read.

It’s winter here, the temperature read out was showing 12-14°C (~54-57°F) over the last few days

Temperature seems ok to low but not sure what Reci recommends. Any chance it froze? I guess you would have glass and coolant all over if it did. Sounds like your settings are correct.

You could have over driven it, especially with a larger supply than it needs… This is not a ‘bad’ lps, it’s more like it’s larger than needed.

My machine was an advertised 50 watt China Blue, that measured 44 watts and has a 60 watt lps.

The tube current is limited only by the lps. When the tube lases, it lases at 100%. If the tube limited the current you could not ‘over drive’ it.

My tube is rated at 21mA, when I tested it at 50% power the current draw was 14mA. Conclusion - when my tube lased it was drawing 28mA.

I set the pot in the lps down so it would draw 10.5mA at 50%. Now it lines up with Lightburn percentage and limits the correct amount of current. I think it does have a faster response time, it would have to be quicker for a higher wattage tube.


I had a very similar issue, and turned out to be the power supply

Did you have something other than a TEM0 state?