Laser stops at higher mA

Hey everyone - finally finished one of my work projects and now trying to get back into the shed only to find my laser no longer likes me.

I noticed that a lot of the jobs I was trying to do needed more and more passes to achieve the same result and sometimes it just did not engrave at all.
I thought it might have been the mirrors or lens and as I have been using the stocks ones I ordered some new ones, they have not arrived yet.

Today I realised that when I turned the laser up over 3-4 mA it was just not firing anymore, could this be an issue with the pot? or more likely the tube?

It could be a number of things.

Do you hear or see any arching above 3-4ma?

When you turn the pot higher does the current increase when you fire the laser?

Hey Don, went and had a look at the tube when firing and at higher mA it is still going and does fire with more intensity but the beam does not appear to hit the first mirror until the mA is turned back down

turn the power up well above 3-4 ma, like 1/2 power.

Put a target at mirror #1 and test fire.

Then Please Post:

  • The current reading on the meter
  • A picture of the burned target.

Hey Don, I put it up to 5mA and with a pieces of paper over mirror one and can confirm that the piece of paper was unharmed.

I moved the paper to the exit of the tube and still the paper survived,
Hold the paper at the tube I turned down the power and when it go to 3mA the paper got hit by the laser

Forgot the photo - so I will get one shortly

At the 10ma* level is there a plasma (purple) beam in the tube??

  • I assume you are reading the 10ma on the analog MA meter.

Is would suggest that the tube is damaged and not lase-ing above 5 ma
the LPS is not outputting the proper power above 5MA

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Hey Don - yes at 10mA the laser is still firing and can see the beam in the tube, though it does appear to curve at the very end

Yup! The visible plasma isn’t the laser, it’s how energy is pumped into the (entirely invisible, far-infrared) laser beam. The anode and cathode are rings at the ends, so the electrically-driven plasma will naturally have to curve a bit to reach them.

I did not see a response to this question?

It might be useful to turn out the lights and open the control panel and laser tube covers from a distance look and listen for crackling or arching around the tube or the LPS.

Keep body/hands away from high voltages.

Hey Don, yeah no crackling that I can hear. everything sounds normal when it is running but I will see if I can see any arcs (my machine is grounded too if that makes any difference).

I have also ordered some new tubes today just in case

Hey Don - Checked tonight and definitely could not see or hear any arching

So I really have no idea what part of my laser is failing, so far I have ordered new mirrors, lens, air assist, & tubes but guess I might as well order a new power supply as it could also be that.

Is there any particular power supply that I should look at?

Here are our current recommendations.

Thanks @mcdanlj LPS (Cloudray) ordered as well now, guess I will just replace items one by one and hope that one of these fix the issue

if your tube was not outputting any power above 3mA of current(at tube output) and you replaced the tube to no effect, checked the wires from the tube back to the LPS for arching then it’s likely the LPS. Air assist, mirrors and lens have no effect on this since nothing is exiting the laser tube. seems like an odd failure and I too would have guessed wire arching at high voltage with higher current.

Need a picture of your supply so you can pick a new one the will not require rewiring.

It is either your tube or your LPS it is often hard to be sure of which one. You said you ordered a tube so I figured you would install that and see if the problem was fixed. Then if not the LPS would be next.

You arent wasting your money in any regard because both these parts will eventually fail.

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I get 404 errors on some of these links.

if you saw ones other than the LPS links I just fixed, just mention them in comments at that page. (Or I guess fix them if you find them, of course…)