Mystery MLine ArIon "peaking" then falling off?

[aryntha]

So, here's the question.

Last year, I ended up with what I was told was a JDSU 2214-25MLUP. Looks like it from the outside, (cylindrical JDSU ArIon casing) but, upon further inspection, it's a retrofitted tube in there one that appears to be "spliced in" with heavy heat-shrunk connections. I BELIEVE it might be a SpectraPhysics tube, (it's a bit smaller / shorter than the normal JDSU 2214 tubes) but i'm not sure. It doesn't "quite" fit, either, so the air holes aren't quite lined up with the heatsinks, but it seems OK when I duct the fan to it.

I was actually upset that it appeared to be 'junk' and not what it was purported to be, (as in not a JDSU 2214-25MLUP) and didn't want to risk a 'dramatic' test failure, so I let it sit. My original rationale behind this was: it also seems like someone at some point ran it without a fan - as part of the plastic shroud near the front is quite melted. So I figured it wouldn't light, or if it did, it'd also smoke. But amazingly, it did light, and didn't smoke. My operation of it hasn't caused any further melting, and the laser certainly works. But its behavior is strange... (to me at least.)

I'd get pictures (I might try) but it's mighty hard to get pictures into the cylinder.
I'm using a normal JDSU power supply, with the JDSU control head. It behaves strangely:

at 4A Idle, it puts out 4 lines; 458, some other blue, 488 and 515.

At running currents, it puts out 7 lines.

at 8a, switching from idle to run, it "peaks" at 65mW and then settles down to 50mW and stays there.

at 9a, switching from idle to run, it "peaks" at 75mW, and then settles down to 60mW and stays there.

At 10a, switching from idle to run, it "peaks" at 100mW, and settles down to 80mW and stays there.

Now the question is -- is this "peaking" behavior, a big 'surge' of power and then a die-off to a settling point -- normal? With such high outputs for a multiline, is it possible that even 8A is too much for this tube and that's why i'm seeing the peak and falloff behavior? I've heard of some NEC tubes (thanks Qumefox) that max at 8.5A, but others tell me that most will do 10A. I'll try to get pictures but there's not much in a picture that would distinguish it from a 2214 except for the splicing. But the behavior is what i'm more interested in, and am wondering if anyone ever saw this kind of behavior or what it could be ... Not enough air flow?

 

[Deleted member 16589]

I have no clue about those types of lasers but it may help if you made a video or simply posted some pictures.

 

[qumefox]

You have to remember the info about the NEC GLG tubes not liking more than 8.5A was going from memory, heh. I'd have to look it up again to verify that. I haven't really messed with argon-ions in a long time. I only came out of hiatus on it for a little while a couple of years ago to try and get some of my parts into working systems to sell. The GLG tubes I was refering to are obvious as to what they are.. The glass bells make them pretty unique.. and no way would they fit in a 2214 cylinder. I think I still have an EOL low pressure tube out of a GLG if anybody needs a big glass paperweight. heh.

As far as the power drop off. I really have no clue. My days of playing with AR-Ions was long before 'affordable' or even really any kind of DIY LPM that I knew of. So I had no idea what the power outputs for any of my stuff was back then. If I had to guess, i'd say insufficient cooling but like I said, that's just a guess. Someone with more knowledge will have to chime in to know for sure.

 

[Meatball]

The power drop off may be the result of those "heavy" heat shrunk connections. Who know how well those joints are actually soldered?

Who knows how much resistance they might be contributing?

Does the current through the tube remain steady as these drops occur?

Can you get an idea if the anode-cathode voltage also drops?

 

[aryntha]

The current does remain steady, yes. I would be able to check for an anode-cathode voltage drop, but, owing to my wonderful laser luck -- my one JDSU PS that can do 10a just died. (The one I was running this with.)

Shut it down, (was working fine), went to dinner, came back, tried to start it up, now the fan on the thing is running slowly and the LEDs on it are dim. Needless to say it won't run any of the lasers anymore.

I have more JDSU supplies but for some reason they only like to do 7.8a.

Wonder if maybe this was a sign of a problem looming in the power supply, and not the laser?

 

[qumefox]

My experiences with the 2214 PSU's is that they'll all do at least 9.5A, however getting there usually requires a custom controller and an external power source. The voltage source provided in the control port doesn't seem to be able to sink enough current to let the regulation run that high, even though the PSU themselves will do it.

The last one I sold would go up to 10.5A using this method with the controller I built. Though the controller was powered by a 12v wall-wart and not off the PSU.

 

[Cyparagon]

Probably. Did you run it in light mode?

 

[aryntha]

I did run it in light mode for a few seconds, if you're meaning the one that died. But not for long, as I noticed it was giving more output than even at 10.5A, so I stopped that pretty quickly. Does this tend to do not-good-things to the supplies? Or are you saying that's the way to get >8a out of the other supplies?

 

[Cyparagon]

Light mode is adjustable, too, so if it is too high, just turn it down. Light mode should eliminate any output power fluctuations. It is better to run them in light mode anyway. Something about eliminating possible plasma oscillations. Current mode often allows for more current, though.

 

[aryntha]

Well, power supply is back in business as in other thread... I will run in light mode from now on though, and i'll try some readings in light mode, too.

Here are some pics -- of what I can see -- in this normal JDSU2114 casing. I know they're not that good, and I likely can't get any real identification of this tube unless I pull it out of the casing, something that may not be worth doing, especially if that shroud has 'melted in place'.

The laser DOES work, it just behaves oddly. It's not a weak laser, either...

At first look, it just looks like a cylindrical 2214:

However the first 'oddness' I noticed was that the heatsinks dont align with the air holes, they actually block them a bit:

Looking into the vents on the front of the laser, first of all, there's a plastic shroud that the normal 2214s do not have. (All that's there is the anode and end of the tube and OC mirror in the case of most 2214s.) -- I noticed that this shroud was quite melted:

I've run this laser (with the fan umbilical attached) for an hour or more, and the melting didn't ever seem to increase. But I'd guess it could be blocking airflow and hurting heatsink effectiveness...

The tube itself is a lot different than a normal JDSU tube, as well. It has a longer 'fill' stem; the JDSUs have a short gas fill stem and it's usually covered with a rubber cap. The tube portion ("bell end") near the HR also isn't nearly as wide, and there's a little "sub-tube" that continues on from the bell, that standard JDSU tubes don't have.

Also, on normal JDSU tubes, the leads attach with two "bolts", none to be seen here, just some heavy heat-shrunk splicing.
It's also thinner and shorter than JDSU tubes.

Besides the fact that I don't know what the tube *is*, what its ratings are, or who made it; it does function, albeit with that weird 20-25mW "peak" (20-25mW above where it settles) on start up that settles down afterwards. It does 50-80mW at 8-10a.

The beam isn't that clean. It is powerful, but not clean... The entire tube seems to be a bit offset in the casing, and it just barely hits the edge of the aperture opening, causing a whole lot of splash and scatter. If I push on the aperture end after loosening some screws, it cleans up a bit, but doesn't want to stay that way.

Also, it seems to produce 7 lines, where as far as I know, the JDSUs only produce 6. That extra line appears to be in the blue - violet range.

So I don't know what it is, but if anyone does have any clue (I doubt the pictures shed that much light on it) , I pretty much just want to be sure I'm not overdriving it, as I know some tubes do top out at < 10a, but as Qumefox said, those would likely be glass envelope tubes...

Thanks for looking anynow.

 

[qumefox]

The number of lines produced is a function of tube current and tube pressure. Generally the healthier a tube is, the more lines you'll get for a given current.

 

[Things]

I think your problem is heat and alignment. I know with my argon, that as it heats up, it actually increases in power ever so slightly. It's highly likely that as your tube heats up, the alignment drifts very slightly, enough to drop the power like you're seeing.

 

[james1095]

Heat related alignment was my initial thought as well. I've only ever realigned HeNe lasers but with those you want to let it warm up for 20-30 minutes and attach the tube or head securely in the position you expect to run it prior to tweaking the alignment. With a random tube shoehorned into that housing it's entirely possible that the cooling is inadequate or uneven. So long as the tube current is holding steady then the connections are not the problem.

Several of my HeNe lasers start out substantially lower and approach peak output as they warm up.

 

[LSRFAQ]

Third party retrofit tubes can do weird things. There is a whole industry of making replacement air cooled tubes. The plastic liner is a give away that this is a retrofit. Cheaper does not always mean better.

Steve