Omni Series 43 Ar/Kr laser problems

Hi all, I'm very new to lasers and this forum. I have an Omni 43 which was working for a while, but won't ignite any more :cryyy: . It was attached to an old confocal that wasn't being used, so I decided to put it to good use as part of a custom-microscope setup I have. It worked for a few months, and I did all the right things I think (always had fans on, tried not to turn on for short periods, ran at limited power etc..). Then it started sputtering and won't ignite anymore. I'm hesitant to keep trying to ignite it because I assume that may do some damage. I've gone over Sam's pages, but it's a bit daunting for me to be honest, and I have other research I need to focus on....

So my options are to a) give up on it altogether and buy a replacement laser (specifically 490nm/532nm, 100mW), b) try to fix it myself and learn a hell of a lot in the process, or c) see if I can get someone to help me fix it. Problem is I'm in Sydney, Australia... and there doesn't seem to be much local expertise.

What should I do? :can:

That's quite a beauty of a laser when its working right.

First off...give us all the details you can. model number, hours on the head if you know them (big help), what was its general output before it dropped, has it been sitting a long time? what model power supply... give us as many details as you can. take pictures if you find it necessary. the more info you give us the better we can help you.

I know the series 43s pretty well. but the 543 and 643 have different requirements to be met and test for, so I need more info. It is odd though, as tubes don't usually just up and quit and call it a day. though sometimes those tubes like to strike down the gas return, its a nasty habit, and can cause that odd flickering you seem to be hinting at. have you tried starting it in current not light mode? can you see a glow in the back of the tube when it is trying to start? ion tubes use a very hot tungsten cathode filament to start. its possible the pressure is incorrect in the tube as well. the power supply could have issues too. troubleshooting these tends to be a long tedious process.

Thanks UltimateK,
After several episodes of trying, then stopping for a few hours, then trying again, I lastly tried a very slight adjustment of the bolts at the back of the laser (which I assume are part of the internal optics)... and the laser sparked and stayed lit... though it may just be a coincidence and I'm not convinced that the problem wont re-occur (I'm leaving it on for an hour or 2 at minimum drive level, which I believe is a good thing to do with these lasers??).

When it was trying to ignite, the full spectrum of laser lines were intermittently available (i.e. I could change the front filter and get blue, yellow, red lines, but only for a fraction of a second).

The reading on the side is 720(hours?).

Unfortunately, as a noob, I don't know what you mean by "strike down the gas return" or "starting it in current not light mode".. The remote input on the power supply just has a dummy connector, so all I've got to run it off is the key-start, the level knob, and the interlock switches.

Is what I experienced with the intermittent failure to stay on an issue with the gas/bulbs/wiring/pressure etc?

Any advice would be great - I don't want this awesome laser to die on me, or go to waste in our lab.

Also, what's the best safety googles to use with this laser? I've got yellow, green and red 'cheap' goggles, and an expensive pair of far-red goggles.. but none will do the job across all output lines.

Model is 643R-LICA-A01
Note quite 10 years old.. It was attached to a confocal microscope, which is now collecting dust...

Ah, so its essentially like new. yes yours is just like mine. only it is a model made for the microscope and is fiber coupled. Nice! mine is made as a normal Free-space lab laser.

Failure to start can happen for lots of reasons with these sadly. but it sounds like it might just have high pressure. these tend to like having the current toward the middle of the knob for startup, especially if it has been left sitting. you should always run it monthly for at least an hour at mid current to allow it to re-bury gas if it has been out of use. the tube is made of a BeO ceramic which is toxic if broken. but as it runs gas gets trapped in it. over time of non-use this slowly seeps back in and can result in overpressure, making the tube hard to restart. if it gets hard to start an oudin coil can be used to help with restarting, or in your case...just turn the key to on, and then turn it immediately back off and let it sit for a moment. if you look in through the side grating you can see the back tubing light up yellow. this is the filament warming up. after a while of not starting it'll cool back down, so you can turn the key again and make it warm up again, sort of 'faking it out' if you will. by leaving it lit for a few moments without starting it can get the tube warm enough to sometimes overcome that hairline jump between starting and not starting, as the warm gas is easier to strike and ionize than when it is cold.

while it is running i'd use the test points to check and see what your running voltage is. it will be a direct function of tube pressure. if it only has 720 hours on it, it's likely quite new like mine. so it shouldn't have any major issues as long as it is being cooled properly by its appropriate fan model. These do get tired pretty fast so keeping them mid to low current will keep their life up considerably as Krypton is expended and buried far faster than the Argon, the entire right side of the laser is a glass ballast supplement for this purpose of keeping the mix correct.

usually for my maintenance burns, I usually do about a half hour to an hour at about 5-6A or so. just enough that i'm getting white. (red, yellow/green, and a couple blues) but before you get all the extra blues and lower gain lines popping in. i'd let it run at mid current for a while and see if that fixes the problem.

Awesome.. Thanks for all the info.. Very relieved that I can continue to use this baby... I will read up more on how to monitor the voltage etc..

Wow, it looks like it has a PCAOM or etalon or
something, very nice. And it either does
676nm red or someone was using it as a
whiteboard?

Yes, it does Red, but only above 50% power. Same for Blue pretty much.

Yeah usually I just get 568 up until a little up the level, then I get two or three blues pretty quickly and then red joins the party last at about 40-50% I think iirc. I haven't run mine in a little while I should probably give it a burn tonight. Usually I don't get 676 and some of the smaller blues until close to maximum. I think I still have some alignment tweaking to do.

Ok ran mine today and I get about 25mW at 6.2A and max current (9.4A) gives me about 97mW, totaling in four blues, yellow, and two reds. Although I don't think my alignment is perfect, but it's probably pretty close.

The problem persisted, and now I have misaligned my mirrors
I'm reading over Sam's pages on realignment.
Unfortunately, I don't have the standby board and I haven't yet figured out how to measure the voltage drop..

I hope that I can realign things and get it up and working again, but I feel I may be going down a bad path if I 'fiddle' with the alignment mirrors any more than I have already.

DanBrown said:

The problem persisted, and now I have misaligned my mirrors
I'm reading over Sam's pages on realignment.
Unfortunately, I don't have the standby board and I haven't yet figured out how to measure the voltage drop..

I hope that I can realign things and get it up and working again, but I feel I may be going down a bad path if I 'fiddle' with the alignment mirrors any more than I have already.

Click to expand...

Shouldn't have messed with them to begin with likely. Realignment of white lights is a real treat. Hope you have a green hene with super low diameter and divergence and a lot of patience...it's a skill that takes practice to be sure.

It sounds like a power supply issue though if it's persisting. I'll check the manual.

Yes, I know - I'm kicking myself as I tried to resist the urge to play with them in the first place, but caved in (that said, adjusting the mirrors did get me going initially, and it became clear that they were misaligned - the light levels I was getting prior to adjustment were very low).

I don't have a HeHe laser yet, but will try and source one... I've read the statements about how realignment is a bitch, and I know I'm going to pay for fiddling with the alignment in the first place..

Does it have to be a HeHe laser for alignment? I have a 100mW DPSS 532nm laser, mirrors and a vibration table etc..

Yes, the bore on these is quite narrow. And not only will you need the hene, but you need a rigid structure to hold and adjust it through the 643 bore while you work. I could do it for you, but shipping would be a nightmare. I'd skype with you if it was possible but being as we live relatively apart it'd be hard. I have a small green hene you could use, but they're not cheap tubes. When I did mine the first time, it was an all morning ordeal.

Thanks. I will continue to read what's required for alignment, and see if I can source a hene laser... At this stage, if it only took me one whole day to get it aligned I'd be more than happy.