Troubleshooting a “no fire” issue

Troubleshooting a “no fire” issue

Quick troubleshooting when the machine is not firing the laser any more.

To begin with, make sure all wires and connections are good in the machine and make sure all cables are where they should be.

1: Start the machine

Check the fuses in the back of the machine in the connector.

2: Do a test fire on the panel

If the machine fires, you dont have a problem 🙂
If the machine do not fire, go to 3.

3: Do a test fire on the test-button on the power supply

If the machine fires, you have a problem in the buttons, potentiometer or the cables.
If the machine do not fire, go to 4.

4: Load a file, or make a shape and try to engrave or cut it.

Only need to test for 5 seconds.
If the machine do not move or fire – you probably have a issue with the bridge rectifier (green in the picture below) and the internal fuse. It is a $1 replacement, soldering needed. Order a new one, 600V 6A is good for the rectifier.

If the machine moves, but no fire from the tube you probably have a issue with the flyback transformer (HVT). Marked red in the picture below.This is a $20-50 replacement depending on where you buy it and how quick you want it delivered. We sell them with EU delivery within 3-4 days here.
Or check out ebay or aliexpress to order a new one. Open your power supply and make sure your is visually identical to the listing on Ebay/aliexpress, there is different types.

Done!

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Comments (18)

  • Tom Reply

    Dear Sir

    Just read your post and saw your picture.
    My new K40 laser will not test fire.
    The seller was very helpful and sent me a new laser tube but it still will not test fire.
    However there is a beam inside the laser tube when I pushed the test fire button.
    They believe the water sensor is not sensitive enough to trigger the laser.
    And they are sending me a new water sensor.

    Is that a possibility?

    Please advise
    Thank you

    8 January, 2018 at 20:37
    • HP Persson Reply

      You can remove the water sensor, bridge P+ and P- on the power supply to test it without the sensor.

      21 January, 2018 at 10:42
  • Rob Reply

    Super-useful, thanks.
    I had a problem with the laser not firing. When I pressed the test button, I could see the ammeter register the current but there was no fire. I switched the whole machine off, then back on again (that one weird IT trick…lol) and it started working again. However, I find this very worrying. Is this possibly the flyback transformer?

    21 January, 2018 at 09:25
    • HP Persson Reply

      It might be a loose connection. Take off the lid on the PSU and inspect the 3-pin connector for the flyback, make sure its crimped properly and you have good contact on all three pins. Also check the machine if it has a water sensor, connected to P+ on the power supply, if these fail the firing can be intermittent. Also check the other cables on the PSU so the crimps are good and no damaged cables.

      21 January, 2018 at 10:41
  • Joel Brondos Reply

    My K40 laser stopped firing in the middle of a project (using LIghtBurn and Cohesion3D Mini upgrade board). e.g. the stepper motor controllers seem to be working fine, communicating with the computer.

    When I click on the Test Fire button, NO CURRENT registers on the analog meter. Just before the laser firing failed, I noticed that the amperage seemed a bit erratic and did not increase or decrease smoothly as I turned the potentiometer.

    If this is likely to be the flyback, I’m thinking I might just as well replace the entire power supply and not just the flyback. Can you recommend any good power supply replacements — ones which could also feed an LED lighting strip and bottle rotation device if I ever should decide on one of those?

    19 February, 2018 at 16:23
  • Gabe Reply

    Hi,

    I can only fire from the test button on the power supply (step 3). Any tips on fixing the issues with the buttons, or wiring?

    7 April, 2018 at 00:37
    • HP Persson Reply

      Make sure the cables from your panel in the lid are connected properly. Also, a test to make is to remove any cables on P+ and P- on the PSU and bridge P+ to P-(gnd) with a small cable to see if the laser is firing after this. A common problem is a flow switch not working which will disable the firing. (test fire on PSU bypasses this protection). This is probably your problem.

      7 April, 2018 at 00:51
      • Tyler Reply

        Hello,
        I am also having a no fire issue, it will fire from the “TEXT” button
        I removed the water brake wires and still no fire, only fire is from the test button
        any other suggesting?

        17 July, 2018 at 04:08
        • HP Persson Reply

          Bridge P+ and GND, pin 5 and 6 if you count from left. Put a piece of cable between them pins and it should fire from the software too.

          17 July, 2018 at 21:50
  • Fran Reply

    Hi. I have an issue with my K40. When firing at low power settings, it works well (ampmeter reads 3-4 mA and laser fires), but when I increase the power, laser stops firing, and ampmeter shows a very low readout (1-2mA).
    Could it be the flyback is damaged?
    Regards,
    Fran

    11 April, 2018 at 15:28
    • HP Persson Reply

      Do a test, on your power supply you have connections marked IN, 5V next to each other. Remove the cables on these two and put in a cable between them, then do a test-fire again. It might be your potentiometer (power knob) beeing faulty, this test shows if it is – you will see very high power so do not run it for long like this. Take a photo before removing cables, or mark them so you can put them back.

      11 April, 2018 at 17:40
      • Fran Reply

        My machine is the one with digital panel, so no power knob. (also I have a cohesion3D mini board).
        I’ll make the test, and see if it fires at full power.

        11 April, 2018 at 20:42
      • Fran Reply

        Hi. I made a video showing some test. Please take a look and tell me what you think. Thanks.
        https://youtu.be/j7POoh3r3NY

        12 April, 2018 at 14:12
        • HP Persson Reply

          Hard to tell, it might be the tube. Have you tried bridging 5V and IN on the PSU? At the same time, quick loss of power can also be the flyback – but it´s often arcing on high power.

          13 April, 2018 at 10:26
  • Pablo Verity Reply

    Also, my K40 won’t fire reliably much below 20%, but it does have some hours on it. For testing purposes, try at least that.

    17 April, 2018 at 12:06
  • Jonathan Reply

    Have you ever heard of or experienced the actual laser tube being the cause of a power supply failure? I recently bought a new k40 machine and the tube stopped firing in the middle of a job. The supplier sent me a new tube and it didn’t work, so I’m now waiting on a new power supply for that machine. I ended up trying the first laser tube in my other k40 machine and it worked great for about a week and then stopped firing in the middle of a job, just like it did for the other machine. Any ideas?

    11 June, 2018 at 22:46
    • HP Persson Reply

      Never heard of it, but it´s a common problem when the flyback dies in the PSU´s. Too warm in the psu compartment, tap water or bad coolant, too hot coolant can do that to the flyback. When you get the new PSU, make sure to upgrade it. Article is on this website 😉

      11 June, 2018 at 22:56

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