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  1. #1
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    new Chinese laser, not lasing

    Hello, brand new to this forum and laser engraving in general. I have a new 400x600 OMTech 55w laser that I just installed and got running today. But I'm getting no cutting or engraving. The laser doesn't fire.

    Details: Initial inspection showed an intact laser tube. I removed the stock fan, heat shrinking the separate wires. Removed the case ground, sanded the paint away and reinstalled wire for quality grounding. Primed/filled the CW300 chiller and ran for several minutes to remove bubbles. Connected all power and flipped on the switch for the control board and laser. The Ruida 644XG initialized fine, and was recognized via USB by Lightburn. I am able send a 20% burn program from Lightroom, and the X and Y gantries seem to work well. However, there appears to be no actual lasing happening. I placed post-it notes in front of each mirror, including the 1st mirror and there's no burning. Same result using the pulse button. I set Min/Max power in the controller to 20/70% w/ the same result. I opened the side panel to look at the power supply, which has its own LCD display, and it shows 0 mA being used by laser at all times. I can see the power supply attempting to activate the laser (laser LED lights and laser symbol on LCD screen), but still 0 mA.

    Any ideas what I should check next?

    Ben

  2. #2
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    Re: new Chinese laser, not lasing

    Will it fire when you push the test fire button. I had a problem where my laser would not fire and I saw that it has a switch to shut the laser off and I had bumped it. Is the water flow sensor working. does your power supply have a test button

  3. #3
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    Re: new Chinese laser, not lasing

    No, it won't fire w/ the test fire button (pulse button on my machine). The laser switch is lit and switched on (when it's switched off the power supply goes black, so the switch is working fine). There is a test button on the power supply, and it doesn't fire using that either. Water is flowing, and the power supply reports that water is flowing.

  4. #4
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    Re: new Chinese laser, not lasing

    The tube only needs power using good electrical connections. It glows pink when operating
    The power supply needs to know the water is running normally, the door(s) is closed, it gets an on-off and PWM signals from the controller. If any of these signals got disconnected it won’t fire. Or if the PS or tube are bad...
    Can you check with the manufacturer?


    Sent from my iPhone using Tapatalk

  5. #5
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    Re: new Chinese laser, not lasing

    Here's a couple quick videos of what I see:


  6. #6
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    Re: new Chinese laser, not lasing

    When you say it isn't firing are you looking at the tube or the spot under the head. If you are not seeing the pink in the tube then it isn't firing but if the tube glows rpink then the beam isn't reaching the lens.

  7. #7
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    Re: new Chinese laser, not lasing

    Tube seems pretty dark, maybe turn the lights off?
    Normally you would work back from what’s broken and find out where the fault lies. In this case the tube is powered by many thousands of volts. You can’t check that with a DMM. I’ve never seen anything that describes a safe way to check a powered tube.
    Depending on your skill level I’d check inputs to the PS first.


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  8. #8
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    Re: new Chinese laser, not lasing

    I've emailed manufacturer, waiting to hear back. @fixtureman1 there's no pink in the tube at all.

    @Dean448 I have a digital multimeter, which input should I check? As the video shows, the PS reports that it's trying to fire the laser so I'm guessing the input is golden. It's either on the output side or the tube itself I think. Gonna be tough to determine which is the problem.

  9. #9
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    Re: new Chinese laser, not lasing

    So most lasers come with a meter that displays mA going into the tube. You can also buy them from lightobject.
    I suspect that a power meter like this will show zero if either the PS or tube is dead, so not sure that will help to determine which one is bad.
    I mentioned a PWM signal. It ranges from 0 to around 5 volts. The higher the voltage the more mA out. My laser generates full power at around 1.5 volts. Tubes need some minimum power to ‘ignite’. The PS could show an indicator light that it’s activating but not enough power to activate the tube. PWM is too low, probably due to a setting in the controller. This pin is worth tracking down and putting a meter on. Adjust power levels on the controller and verify that the voltage changes.
    If all this proves out, and the PS appears to be functional, it probably says the tube is bad.


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  10. #10
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    Re: new Chinese laser, not lasing

    Thanks for the suggestions. I was able to get a response from the manufacturer. In trying to troubleshoot I was able to get a closer look at the laser tube. It's got water leaking into the innermost CO₂ tube. Found a larger crack on the cathode side that explains it.
    Attached Thumbnails Attached Thumbnails crack.jpg  

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