No fire troubleshooting

No fire troubleshooting

This guide will help you identify and solve most problems with your laser machine not firing the laser beam.

Make sure your K40 turns on and homes to zero position.
If it doesn´t, check the fuse in the rear power connector before continuing.

Step 1

Turn on your machine.
Open the lid on your panel and push the test-button located on your power supply

This is good, your PSU and laser tube is healthy and working.

Go to Step 2

The most common problem when the machine is firing with low power, and mA-meter showing 2-5mA no matter what power setting is set – the flyback transformer is often the issue.
This part is avalible at ebay, aliexpress or in our store. Make sure to visually identify your type of rectifier before ordering one.

If you want to step your game up a bit – upgrading to a HY-T50 is a good upgrade, this PSU does not have the issues the K40 power supply has.
Avalible on amazon, ebay and aliexpress.

You have a issue with your PSU or laser tube.
The flyback transformer might be the issue but there is no guarantee it will solve your problems.
I suggest upgrading to a HY-T50 instead of buying a new K40 power supply (not sold by us).

This guide cannot identify exactly your problem any closer than this.

Things to try:
– Make sure you have grounded the machine properly – see this article
– Check all internal connections for breaks, bad crimps or loose cables.

Step 2

Turn on your machine.
Push the test-button on your panel, and/or through the software you are using with your machine.

Great – you don´t have a issue with your machine 😉

You probably have a issue with the protect function of the power supply.

Try this:
– Put a bridge or small cable between P+ and P-(gnd) and test the machine again. If it fires it´s whatever security solution connected to these pins that are your problem.
Often a flow sensor is connected, inspect it and sometimes it can be adjusted to allow for less flow/pressure.
You can also find flow sensors in our store.

If you have upgraded your controller:
Make sure the power supply, any extra 24V power supply and the controller is grounded to the same point, often the ground bolt in the back of the machine.
You can also put a small cable between the laser PSU ground to the screw terminal ground on the Cohesion3D controller.
Same solution with other controllers, make sure they are grounded on the same spot.

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Comments (12)

  • Richard Reply

    Thanks for this guide. When I test fire the laser both with the test button and the power supply test button there is a clicking but no laser. Do I need to replace both the tube and the power supply. Which would you suggest to do first? Seems a waste, is there anybody who recycles these?

    2019-01-06 at 23:31
    • HP Persson Reply

      Without doing a high voltage test its a chance. The tubes doesn´t die quickly, they fade away in 9 of 10 faults with them. But the PSU often dies over a second. I would go with a PSU to start with, or only the flyback transformer.

      2019-01-07 at 18:43
      • Richard Reply

        Thanks, I will do this. You mention elsewhere on this site the Hy t50 PSU..can this be used with the k40 or will it be ‘overpowered’? I have the digital readout – yet to install a mAmmeter.

        2019-01-08 at 17:51
        • HP Persson Reply

          Hy-T50 will work good on the K40. Just keep a eye on the mA-meter not to over power the tube. I have changed to T50´s in all my machines, one even have a T80.

          2019-01-08 at 23:17
          • Richard

            Ok, I have just ordered one, will let you know if it fixes my machine. Thanks

            2019-01-09 at 17:26
  • Sophie Moore Reply

    Hi Ive been searching high and low and you have identified the problem!
    I bridged my p+ and GND on the PSU (type 2) and my laser fired at last.

    Now – i dont have a flow controller anywhere on the machine that I can find, so how do i go about fixing it? Or should I install one?

    I have nothing in my k+k- port (PSU type2) and my P+ GND (PSU type 2) plugs into P+ and p- on control board.
    I have a JK-K3020

    please help, ive been trying for days!

    2019-02-13 at 03:53
    • HP Persson Reply

      If you do not have a flow sensor, you can bridge P+ and GND, just make sure you have water flow before using the machine. If you have the digital panel some connectors will be missing, it test-fires through another pin so it´s ok with missing cables on K+/K-

      2019-02-13 at 08:50
  • Alessandro Reply

    Hi HP, I’m posting here because a friend of mine asked me to fix a faulty K40 laser. Basically when I light up the machine the laser head starts aligning bottom-right instead of up-left and the motherboard seems to work fine: the laser doesn’t fire at all even when I press the test button, no fire, no noise, nothing, even the amperometer seems dead. I’m working on, as my friend says, a new power supply but I did a mess so I’m trying to figure out what is wrong.

    Is there a way to test if the flyback transformer is working? Which voltage should go to the flyback? Thank you a lot, you are the only one who can help me 🙂

    Alex from Italy.

    2019-07-08 at 10:10
    • HP Persson Reply

      Homing down and right is probably the end stop no connected or broken, when it doesnt get a signal it goes the opposite direction. Check the end-stops – both of them as they are going wrong direction. The flyback should not be measured at all – it´s 12-16000 volts in that one and you need special meters to measure it properly without dying 🙂 There is a redneck-test, putting the positive lead aprox. 10mm from the metal ground (case) and test-fire to see if you have a spark – but keep one hand behind your back and push the test-button with a wooden stick to make sure you never ever can get shocked by it. I always suggest bying a new flyback instead of doing a test like that, they are like 20-25 USD + shipping from china. You can use this pic to see what´s going where on the power supply ->

      2019-07-08 at 11:50
      • Alessandro Reply

        Perfect, I’ll give a try soon. Thanks for your support and compliments for the site 🙂

        2019-07-10 at 15:15
  • casey Reply


    Had a problem with my k40 laser tube arcing after rastering something, went to the cut command and lost laser power quickly over 2 seconds. Lots of arcing. After investigation, I noticed the laser was arcing inside the case. I had previously thought it was arcing outside of the tube because of a small black spot on the backside of the laser tube, but after putting silicon on it, I retried and seen it was arcing from the anode. I added silicon there and now no fire. I had a lot of condensation and everyone acted like that was a big no-no, but its 85+ degrees out and 90% humidity, 15-20C makes my tube condensate like crazy. any advice on my condensation problem? also, would you guess that the laser tube is just bad instead of being the HVT? laser still has movement, just no power.

    2019-09-04 at 04:59
    • HP Persson Reply

      If it´s arcing the PSU is good, you might kill the HVT with arcing though. I have 120mm computer fans added on each side of my laser tube, one pulling and one pushing on all my machines, it cools down the tube slightly from the radiated heat and moves the dew point further away. Some machines has a hole for longer tubes, put the fan there. You can try with one pushing air in to begin with.

      2019-09-05 at 09:34

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