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Thread: Omnichrome/Melles Argon - Starting Issues

  1. #11
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    Philadelphia is about an hour or so drive from here, that's cool to find out Sam is so close He may have some info seeing as how if it weren't for him I wouldn't have even known how to wire my laser

  2. #12
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    i found a jumper inside the power supply which is supposed to disable the control circuity and just run the tube at full current, it does the same thing it has always done by running for about 1-2 seconds then going out.

    looks like i may have to pay Sam a visit (not that it's really a bad thing)

  3. #13
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
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    .

    looks like i may have to pay Sam a visit (not that it's really a bad thing)[/QUOTE]

    If your school offers college tour days :-) use one!
    Seriously, get a look at a major school like that and see Sam in the process,
    its hard to get good students any more who dont want to be Masters of Business Assassination (MBA DEGREE) (every MBA I've worked with killed the company) The physics or EE dept might ofer you a scholarship etc because of your interest in technology.

    Steve

  4. #14
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    I ended up buying this laser from him and unfortunately the power supply might be toasted. Any schematics of the 170B supply are appreciated, especially of the interlock system and front panel sub-circuit board.
    Last edited by drlava; 12-06-2007 at 12:07.

  5. #15
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    Allright, through some reverse engineering I was able to reconstruct most of the interlock circuit and repair that damage in the power supply.

    So now the laser will pulse on but not start. Filament voltage is 3.3V. When the unit begins the filament preheat, the tube voltage is slowly ramped up to 130V (0A tube current), and holds there until a relay clicks and the PSU begins the starting pulses and during this time the tube voltage is at 165V.

    Are these typical for the omnichrome 170B?

    Is there a way to tell if the PSU is tripping out due to high tube current?

  6. #16
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    For the sake of completeness I will make one last post about this. The laser is now working. The problem, besides a shot trace and a transistor and diode in the interlock circuit, was that an FET was blown in the main switching regulator.

    The way to diagnose this, now that I have experience is easy: when the supply is in the preheat mode with all power and relays on, the tube voltage should be 0V. Once the preheat mode is over, the tube voltage should ramp up to 169 or so. If the tube voltage is at line potential during the preheat phase, you know that one or both of the FETs are shorted.

    Some experienced tube users may know this, but no one diagnosed it from my previous post, so here it is for future reference.

    The tube seems to be good, running 105V at 8A.





    I'm now in search of some multiline optics!

  7. #17
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    that's good to know what those symptoms turned out to be.

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