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Thread: Lowering a high-pressure medical surplus krypton laser

  1. #1
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    Default Lowering a high-pressure medical surplus krypton laser

    I picked this Coherent Novus Omni up from a local scrapper for $200 as a winter project that's been a lot of fun so far.

    I had to haul it home in a blizzard, so the radiator froze and I had to solder 14 splits, but the tube was fine and there are no leaks in the system now. It had a 3phase config, but the only modification I needed was to bypass the lower current breaker and pick the right 2 wire. Draws 65A from 240V at full power - yikes. It failed a few self-tests, which I was able to bypass by soldering a different connector config for the interlock. The service manual was invaluable. (I tried to attach a copy here, but size limit) I also removed/bypassed the fiber launch. The main issue is it's high pressure. Tube voltage is 253V+ and it's supposed to be 208V.

    The HR is selectable between red or yellow+green. I've got a great red beam from it - 1.8W at 40A tube current which is above spec. But I only got an intermittent flicker of green or yellow at first, and after running a bit I have nothing even at full tube current. Auto-align fails because of this. I'm relatively certain this is because of the high pressure.

    I've run it at low current for a total of about 2 hours, and at high current for a total of about 20 minutes. The computer says there's only 45 hours on the tube, but since it was for surgery, computer also says it's had something like 800,000 pulses (effectively, tube starts). I've no idea if this is a lot or not.

    I still have high pressure after these runs. Does krypton laser pressure lower with run time like argon does? If so, what sort of time frame is that? Are there other methods, preferably ones that don't involve an elaborate vacuum setup? Is this just a RED-ONLY laser now? I could live with that. It's made friends with my HGM argon
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  2. #2
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    Thank you for sharing pictures of your laser. I never tire of seeing gas lasers. Hopefully someone can answer your question.

  3. #3
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    Default

    It will come down with time. That is the pulsed version of the Innova family magnet, it is not cooled well enough to run CW all day. Giveaway is the white tape outer covering. Depending on which version of the tube that is, I'd disconnect the auto fill system at the connector to the solenoids if present. Despite what the literature says, the front optical assembly can be tuned on those, and often that does it. Peak the front mirror running red for the least tube current when in light mode. Then run the yellow/green software, Often that does it.

    You would really have to run it for weeks at maximum pulse to get the pressure down.

    Depending on which version of the filling system you have, I can pull it down, I have the compression tool that seals them off, and the 6 nines krypton, and the turbopump. So few of the tool are sold anymore that they now cost 3700$. Doing it without the sealing tool kills the laser, trust me.

    You really don't want to do that however, because if the tube characteristics don't match what is in the ROM, the PSU gets angry and shuts down.

    Yellow likes a lower magnetic field and lower pressure.

    Edit, I had my tube assembly backwards in my mind. . Been a while. OK, I see the red tab on the fill assembly. Carefully mark which wires go to ready and fill solenoids and disconnect so it does not autofill for a long while.

    Steve
    Last edited by mixedgas; 01-11-2021 at 09:17.
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  4. #4
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    Default Your Coherent

    I had the same model hanging out in my garage for several years. I dismantled it after finding the power supply was good N cooked. cool to see one of those running.
    Will there be three phase!!!!

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