Bad Co2 tube ?

I left my laser project sit for a month. My co2 worked great when I first set it up. I made a stand for the tube, set up cooling tower etc to make it a usable set up. http://laserpointerforums.com/images/smilies/angry.gif But when I fired it up the beam could barely smoke a wooden pencil. it left just a faint burn ring. Before it would have set the pencil to flames :cryyy:

Measure the operating current.

Im sure the current.is fine. i have power supply that came with the tube. do these sometimes just be bad tubes. or the cavity mirrors not good?

trussmonkey25 said:

Im sure the current.is fine.

Click to expand...

Did you ask for advice or not? Rule out that the power supply is failing by measuring the current. It takes less than a minute to check; quit being lazy.

Ok ill borrow a meter. lol. what amperage should i read? I have .022 amps when fireing. That doesn't seem right.

22mA isn't far fetched, this is a multiwatt CO2 tube, not some HeNe. Look up a spec sheet for that wattage of tube (I don't think you specified?) to see the normal operating current.

he has a 60w tube in the list of owned lasers, so 22mA is about right...
is there junk on the output coupler? what is the color of the discharge, if any?...

You mentioned that when you tried to burn a pencil and it would barely smoke it and just leave a "ring". This sounds like it "could" be an alignment issue. I know these Co2 tubes don't have adjustable mirrors but that's what it sounds like to me. Can you burn something and take a picture of this "ring"?

I would also make sure you check all of your connections and make sure they are all secure.

What color is the plasma discharge when running?

Plasma color will be a very important clue.

By the way - a doughnut-shaped ring output is a more normal operating TEM mode for CO2 lasers than not. Its just that the high power tubes put out enough power in the center of the mode to give off the appearance of TEM00. But the beam will rarely if ever be TEM00.

The fact that you are indeed observing the ring shaped output is only an indication of low power in the beam.

it was a faint 2 mm ring burned into the wood . I know when it was working the further away it would burn a nice 5 mm do nut into a board with just a quick pulse. i guess you could say a lite pinkish purple lavender color

hmm, lavender doesn't seem right. how about violet or tulip with a hue of cinnamon?

or better yet-post pictures of it not working, not the donut output, but the plasma.

is the discharge uniform along the central tube? any abnormal hissing noises coming out of it? smudges on the output znse window? i know that if i burn things up close, smoke can deposit on the window and fog it. it happened twice and i cleaned it with acetone without any visible adverse effects

A little smudg can stop a 60 w laser ?? No the plazma dances around thee cathode end a bit for a few second the all a sudden goes straight and even but no output

how little is a little? it will stop it alright if it bakes onto the window and cracks it.
your pic is totally out of focus...can you maybe take a decent photo from above of the entire tube glowing?

I think that the plasma color presents itself as normal. You don't want to see any hint of peach, pink, or orange. It should be a light violet - close to lavender, or a white washed violet. The nitrogen gas fill in the tube would be normal then. Your Helium and CO2 fill should also be okay.

This is tricky now. I thought the color would be way off. But you've got 22mA through the lavender plasma, the only thing that could hold it back is a dirty output coupler.

If optics appear to be fine, and the current through the tube appears to be stable and the optics are clean, there are only two things left:

Gas mix appears to be fine, but is still off - a slightly bad gas mix could greatly affect power, but its strange to think that a sealed glass tube has "suddenly" began to leak come to pressure.

The optics are mis-aligned. While the tube is supported on only two supports on either end, try giving the tube a light press down in the middle (where its not supported) to see if power changes. Rotate the tube some 20 degrees and try again. Keep doing this until you otherwise see a change in power.

I'm not entirely sure what could cause a tube to suddenly become mis-aligned, but the odds of it happening are much greater the longer the lasing cavity is. A 60W CO2 laser has a significant length to it.

See what happens after you clean the output coupler and "bend" the tube around a bit.

Do not break that tube.

trussmonkey25 mentioned that he made a stand for it. If that stand is applying pressure to the ends of the tube, maybe it could indeed be an alignment issue.

pop it out to its original position when it used to set pencils on fire and try again...

Hmmm. that. I can. try. bofore i just had tube resting on foam pieces.. I just mounted it...i can try loosening up the mounts. yes I know glass has some flex to it.....output couples ? Is that just the + connectors...the screw together thing.
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