When is a Chinese laser tube 'dead'?
The laser tube in my XYZ-made laser has had an easy life...
It's basically a retirement hobby, so sometimes the laser doesn't get used for several days in a row.
The tube has lasted almost 3 years so I've been expecting it to 'let the magic smoke out' for some time now.:stickpoke
On the latest job, it almost finished cutting through some 3mm MDF pieces when the power level seemed to briefly increase (indicated by a lot more smoke and burn marks on the top) for about 50mm, then nothing....
The tube is still glowing violet, and if I leave the job overnight then on startup the first 100mm or so works as it should - but then power drops off and stops as above.
So my question is to anyone who has had a tube die: is this how it goes?
And if it's dead, why is the tube still glowing? :confused:
Thanks!
Bob
Well, it's not the tube !
Changed the tube today, didn't need much to re-align it fortunately.
Started off the same job it was running yesterday...
The engraving part went ok.
The outline cut started off ok, and in fact did about ¾ of the circumference of the job... and I was rubbing my hands and thinking 'Great, I'm back in business!'
Then it the power level went UP (flame2) and started burning for about 80mm, then dropped right down to the point where it was barely making a mark - and finally, power dropped to zero (but tube was still glowing) :(
So whatever it is, it's not the tube - and I've wasted a day putting the new one in - but at least I now know: The old tube may still have some life in it, and the new tube still works after sitting in storage for ~ 3years.
I guess the next thing is to test the PSU, and I'm not sure how to go about doing that - other than getting another one 'on spec' and hoping that will fix the problem.
First off, I'll put an ammeter in line on the cathode end of the tube (negative line) and check the actual power when it fires initially and when it drops back.
The laser came with a huge wire-wound resistor and a sheet showing how to use that instead of the tube to test the PSU.
I've never tried it before because the instructions are far from clear (and the photo shows the meter's needle hard-up against the maximum pin-stop!) and, of course, I've not needed to up to now.
One thing to be tried first though, is checking the PSU isn't full of dust-bunnies, or my case - cat hair.
It does sound like it's the high voltage PSU though - just as well there are plenty of them on eBay etc.