Power Supply or Laser tube

Ok so here is my story.

Everything is wired properly AFAIK. Ground is ok.

This is my initial test fire. Check the linked video:

Notice before arcing the sound it makes, it still does make that sound whenever I hit test fire.

i researched and added a bit of insulating silicone to where the arc starts from as there was a spot missing it.

From there onwards whenever I press fire, the same sound(not the arcing the other buzzing sound) appears and the gauge is stuck at 4-5ma regardless of how much voltage I put into the IN pin(after a minimum voltage).

I wonder if it is the laser tube or the power supply which I need to replace!

Can you assist me, I am lost…


  • I am using two power supplies, one 24v through which I power everything and the LPS which I only use to power the laser.
  • Their grounds are both connected and they are both earthed together as well.
  • Test was done using 4V on IN.
  • I never seen plasma in that laser.

Unfortunately i converted everything before checking if it worked :frowning: just to figure that out in the end.

The laser does not seem to be cracked or otherwise damaged but I have limited perception :slight_smile:

I thought I’d read in these forums that arcing like that can damage the LPS. It’s essentially a short circuit. Is there’s now no arcing and it still doesn’t light the tube, the LPS could be bad.

Also check that the wire at other end of the tube is properly routed to the milli-Amp meter and then to the L- on the LPS.

Checked it is, it goes to the amp meter(black wire) and then after anmeter leaves a yellow wire that goes to L-. After adding a bit more of insulation(silicone) near the red wire where it arc’ed it no longer arcs it maxes at 4-5ma with 5V in and just makes the sound you can hear in the video(when it’s not arcing).

I would guess you have a bad tube because:

  • Arching like this at the anode usually means there is no load on the LPS, i.e. tube dead.
  • The hissing sound is the HVT in the LPS breaking down due to no load.
  • You checked the cathode ground and you are getting a current reading inferring the cathode is grounded.
  • The tube never lights up

Are you sure the tube is not cracked sometimes it is hard to see them?
Are you running coolant and are there any leaks?
Is this a new machine?

My guess is the LPS is still ok since it puts out a strong arc.
Arching like this can damage the LPS
At this point, you could have damaged the LPS but there is no way to know until you verify the tube is good.

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It is new that you see is the first fire.

So I have opened the LPSU and it was clean. I tested the diodes you often mention and they were good. There was nothing that made me believe it ever released magic smoke or something else broke. Still this is from an unexperienced point of view.

I am running distilled water and there are no leaks. It seems that the tube is mostly non conductive.

It is a new machine, but it was entirely modified already. Regardless, all modifications aside, no 24V or 5V output on the LPSU and 5V in it doesn’t power the laser.

After trying again, I went back to arcing, this time the anmeter measures basically nothing. I’d assume the tube is no longer conducting at all, so it just arcs to the frame.

Still would the anmeter ever measure 4ma with the tube dead?

If it is a new machine I would go back to the seller for a new tube.

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Just did so, seller was vevor so I hope they will send a new one for free.

I hope I didn’t break the LPSU.

I will report once I have news, it may help someone else.


Ok VEVOR are replacing the tube, no questions asked so that’s a great start. I’ll report once I get it.


So 40w tube was out of stock so they sent me 50w, which I’ll be setting up shortly.

When removing the old tube one thing I noticed was that it had water in all of it’s compartments. I assume that’s not supposed to happen right?

I couldn’t find signs of any cracks or the like though.

The water should only be in the water jackets.

Also I’m wondering if it’s fine to use a 60w power supply with the 50w laser tube?