Need Help!- Is my laser tube dying?

[tonycsouth]

Over recent days the desktop laser has developed an intermittent failure to fire the laser.
The problem started after some fairly constant usage, which saw the effectiveness of the laser gradually fade. Water temperature was warmer than body temp. to the touch, so I suspect that the tube had overheated.
The following day I turned the laser on and started a cut only to find that the laser wasn't firing. Tried a few test fires, nothing happening. Turned on/off a few times with the same results.
Then out of the blue the laser started functioning again. I found that by looking towards the rear of the housing I could detect a glow through the mirror pass through aperture when the laser fired, along with movement of the needle in the current indication meter. But again the effectiveness/power faded after a short period of time.

Now, today it appears to fire ( the glow at the rear, needle movement), but no actual laser beam. I have placed a piece of paper in the path of the beam between the various mirrors with no effect to the paper.

There is water flow, and everything appears to be normal. Is it the tube dying, or possibly another electrical problem?

[SkipW]

Tony,

Check all of your wire connections on the tube and power supply. I'm not sure of your setup, but I've had similar problems in the past that have been corrected by checking and re-tightening my power supply wire connectors.

That may not be your problem but it's a good first step.

[tonycsouth]

Skip, thanks for your reply.
Towards the end of yesterday I decided to check the tube and found that the mirror cooling ring at the exit end of the tube had come adrift, the glue having let go.
So it appears that I have cooked/burnt the exit mirror, as the tube still fires strongly, but no beam exits the tube.
I am now in the process of redesigning the coolant delivery system to include a flow meter, temp sensors in and out, inline filter, and radiator.
A new 40W laser tube has been ordered on Ebay from China, but a word of warning, check the vendors whole site before ordering as I later found the same tube for $65.00 less elsewhere on their site.
So I have a week or so of down time in which to look at any improvements I can make, and do them.
Ahh, the learning curve.

[underhide]

Hi Tonycsouth,
Just wondering if you resovled this problem as we are having the same problem and really need some help. Cheers

[Melody-gweike]

Hi， tonycsouth,

What did the am meter show? The normal for 40W is around 20.

If it shows smaller than 5, then there are probably some problems with the tube.

[underhide]

Thank you for your help. I am a bit red faced as I think all the problem was was dirty mirrors. Cheers

[jeaves]

Hi. I have had similar problems, but it isn't my mirrors. I think the tube is bad. Can I ask where you bought your tube? I have to buy a 40 watt tube, and would rather pay for a cheaper one than buy one through a company here in the states (which probably originates from the same company in China, anyway). Thanks. - jeaves

[underhide]

Hi Jeaves, After much trial and error our problem ended up being a loose mirror in the housing. Once this was discovered and we made sure that all mirrors were tight, bingo. Are you getting a pink light in your tube when you fire it?
We got our machine and tube through Redsail, China. cheers underhide

[kadeR]

Originally Posted by Melody-gweike Hi， tonycsouth, What did the am meter show? The normal for 40W is around 20. If it shows smaller than 5, then there are probably some problems with the tube.

for an 130W tube what is the normal mA in 100% of power?

Tks

[jeaves]

Hi, Underhide.
I am going to either buy a tube or a power supply after I find out which is faulty. My mirrors are all good, so my problem must exist elsewhere in the machine. I did read your post and double-checked my machine to make sure that I wasn't dealing with the same issue. - J