Question about mA Meter on Chinese Laser (With Video)

[Brian Leavitt]

Jeff,
Nothing changed operationally with the laser after adding the mA meter. If it had, I would already have removed it. It still engraves and cuts exactly how it did before the meter was there. My main question was just why does the meter only register if the power is at 29% or less and the tube whines.

[Kev Williams]

The tube shouldn't make no noise... I seem to remember from reading a few threads, that a whining tube is indicative of it arcing somewhere. I think someone even posted a video of his tube doing this...

anyway, the fact your meter isn't reading much is also indicative of an arc. Did it whine before the meter?

[Brian Leavitt]

The tube shouldn't make no noise... I seem to remember from reading a few threads, that a whining tube is indicative of it arcing somewhere. I think someone even posted a video of his tube doing this...

anyway, the fact your meter isn't reading much is also indicative of an arc. Did it whine before the meter?

Yes it did the whining before the meter as well. It only does that at 29% power and less, though.
I was trying to find a photo of a glass laser tube while firing at the output end, but I didn't come up with anything. I'd like to know what it should look like within the last 4 inches before the output lens while firing.

[Scott Marquez]

Jeff,
Nothing changed operationally with the laser after adding the mA meter. If it had, I would already have removed it. It still engraves and cuts exactly how it did before the meter was there. My main question was just why does the meter only register if the power is at 29% or less and the tube whines.

The meter is showing you "current flow", so use what it is telling you for trouble shooting, my guess is that you should be seeing over 15ma. After checking all of your electrical connections, including your ground, you might start playing with your software output levels
If all else fails, purchase a new power supply and 60 or 80 watt tube and enjoy.
Scott

[Brian Leavitt]

I'm looking at a replacement tube options right now. It has a power supply for up to a 60 watt tube in it already and I'd be looking to get a 60 watt tube. The vast majority of my laser knowledge relates to american-made lasers so this Chinese machine is a different kind of beast. If I can get away with just replacing the tube, I'd rather do that than replace the tube and power supply. This laser is not a money maker for me. I have better ones for that, but I do enjoy using it and want to keep it going. I'm going to go over the electrical connections tonight, if I have time. I'm also going to buy another mA meter for testing since they're cheap. I've read of others having problems getting a proper reading on these types of cheapie lasers.

I did some more brief testing last night. I can cut through 1/8" plexiglass at 85% power and 6mm/sec speed. Pretty slow, but it cuts through clean and actually makes a very nice edge. In the short term, I'm going to just run it as-is until it actually dies. After that, it's upgrade time. Better laser source, better optics, and beam combiner for a red dot laser are in the future plans. Maybe some day I'll actually try to make some money with it.

[Brian Leavitt]

I just had a thought. I wonder if my cooling liquid has something to do with the behavior of the laser tube. I've been running RV antifreeze in it because it's in my unheated, uninsulated garage. I'm going to try some distilled water and see if anything changes.

[Jerome Stanek]

I have been running RV antifreeze in mine for 3 years without any problems

[Brian Leavitt]

Are you running 100% antifreeze or are you diluting it, Jerome?

I've read that antifreeze can potentially cause internal arcing of the tube, but I don't know which type of antifreeze that is referring to.

[Jerome Stanek]

I run the stuff that Walmart sells straight

[Bill George]

I have ran both when I had my glass tube laser, but mA meters don't lie. Changing anti freeze will not help, sorry.

[Bert Kemp]

If the problem is arcing? and I don't know that it is, but putting in distilled water might help. When that tube fires it looks funny. and he says it makes a noise.

I have ran both when I had my glass tube laser, but mA meters don't lie. Changing anti freeze will not help, sorry.

[Doug Fisher]

I wouldn't buy a tube until you confirmed everything else is working correctly. Are you sure the whining isn't coming from the power supply itself? Have you done any testing/confirmation to make sure your mA meter is actually functioning correctly?

[Brian Leavitt]

The noise is coming from inside the tube, and I can also hear it at the point where the laser beam hits the substrate it's engraving. It sounds like an RF laser making a cut at a lower Hz setting, which is what makes me think there's arcing in the tube.

I have not tested the mA meter. I'm buying another one to swap in for testing. The laser fires so the mA meter is not giving me the whole story. I'm going to try distilled water just to see what happens. It's a cheap and easy test.

[Brian Leavitt]

Replaced the antifreeze with distilled water. Interestingly, it still makes the noise, but only at 19 power and below. Also, the visible beam inside the tube is more consistent and stable at the output end now. Still no reading on the mA meter, but I have another one on the way. We'll see...

I did go ahead and order three new mirrors, new focus lens, and a beam combiner setup. My mirrors look more like dull pieces of steel than mirrors so I know I'm losing a lot of power and beam quality. Looking forward to getting them replaced. The focus lens on the machine looks OK, but it has a convex side and a slightly concave side. I've never seen this in a lens before. I decided to replace it so all of the optics will be new and much, much higher quality.

I'm not going to be replacing the tube for now. I'd like a higher quality tube, but since the one I have is still kicking I'd feel like I was wasting it. Gonna wait 'til it dies to replace it, whether or not I can ever get a mA reading off it.

[Bill George]

mA meters don't lie. The tube is made of glass, glass is a insulator, unless the tube has a flaw or you have a bad ground connection it should never try to arc.