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Thread: Melles Griot 05-LHP-991 operators manual

  1. #11
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    Quote Originally Posted by tolland View Post
    How would I test the brick? It would seem I would need a 3500V/6.5mA=538.5 k Ohm load that can handle 22 watts....
    One does not test bricks with loads. One tests HENE system parts via substitution. The cost of setting up a test load that is non-inductive, and can gradually load the PSU multiplier stage exceeds the cost of a surplus Psu brick. Even if you see the 6.5 mA, what you cannot see is the weak 15 kV open circuit start voltage that is needed. The required HV probe, if you do not have one, is ~170$, and another 50-60$ for the resistors. Common carbon and metal film resistors break down under the HV stress, you'd have to purchase a large string of high wattage resistors and distribute the load.

    To test a PSU on a campus, I'd use another hene head or a spectrum tube (maybe neon sign tube) and a ballast resistor. If I used the spectrum tube, I would not leave it on for more then 10 seconds, as it is still not a matched load for a PSU.

    PSUs like to be properly loaded, and they really die quickly from internal arcing without the capacitive load of a tube across them.

    Trust my experience on this. If the fuse is popping on the line side, the switching power supply output stage that drives the internal transformer inside the brick is effectively shorted. More specifically, because you see a flash of red light from the tube and it goes out, then pops the fuse, the current feedback loop can't close. The little igniter transformer is firing, but the main HV stage is not. This almost always indicates damage on the low side of the step up transformer in the brick.


    Where are you located? You might be amazed at the resources we can locate via PL. I'm a former university research associate with 20 years of working with gas and scientific lasers and 10 years of working with high voltage sources. If I know where you are, I can usually locate some one who has other HENEs, often on the same campus.
    The laser community is a small one, and does lots of networking.

    Steve
    Last edited by mixedgas; 08-04-2014 at 03:52.
    Qui habet Christos, habet Vitam!
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  2. #12
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    Quote Originally Posted by mixedgas View Post
    Where are you located? You might be amazed at the resources we can locate via PL. I'm a former university research associate with 20 years of working with gas and scientific lasers and 10 years of working with high voltage sources. If I know where you are, I can usually locate some one who has other HENEs, often on the same campus.
    The laser community is a small one, and does lots of networking.
    I am in East London in the UK. The kit was donated by Imperial College, so I could go and have a chat with them once I have some sensible questions to ask ;-)

  3. #13
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    Quote Originally Posted by tolland View Post
    I am in East London in the UK. The kit was donated by Imperial College, so I could go and have a chat with them once I have some sensible questions to ask ;-)
    Send a PM to Jem and Norty, they should know some on in the UK who can get you sorted.

    Best,

    Steve
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  4. #14
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    Quote Originally Posted by mixedgas View Post
    One does not test bricks with loads. One tests HENE system parts via substitution.
    I managed to borrow another PSU, and the laser is working now... Now I just need to source one I can use permanently.

  5. #15
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    Quote Originally Posted by tolland View Post
    I managed to borrow another PSU, and the laser is working now... Now I just need to source one I can use permanently.
    Very old thresd I know, but no one seems to have noticed that it is wired for 110V in your pictures. disconnet the white wire from the fue, insulate it and connect the blue wire from brick to the fuse and you should be good to go.

    Robert.

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