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Thread: ULS M-300 Laser not firing

  1. #1
    Join Date
    Jul 2009
    Los Angeles

    ULS M-300 Laser not firing

    We have an older ULS-M300 35Watt laser engraver. The original tube lasted almost 8 years, but the replacement tube abruptly stopped working after 2~3 year of very limited usage. We did contacted ULS and was told we needed the tube replaced. Given how little usage the replaced tube saw before it stopped working as a backup laser engraver, we mothballed it instead of replacing the tube again.

    Anyway, having found a 3rd party tube service company on this forum that has good reviews, we want to send the old tube in for recharge. However, we want to make sure the problem is with the laser tube.

    The tube failure on the M-300 replace laser was very abrupt. Instead of a gradual decline in power output, it just stopped working. Everything else works. The door/safety interlocks works, the red dot laser works. When set to alignment mode, the green panel led turns off, the buzzer turns on, but the laser does not fire. Even at 100% power, 25Khz setting, the scotch tape in the laser path shows no sign of melting.

    Before we send the tube in to be recharged, is there any way for us to check to make sure the problem is indeed with the tube and not something else.

    We have basic electronic troubleshooting skills with mutli-meter and oscilloscope. We have also replaced a Z axis driver board on our PLS before.



  2. #2
    John, I'm afraid I'm gonig to be a little helpful. There was a thread many years ago where someone pulled apart a tube's electronics to find a bad electronic component. They fixed it themselves very inexpensively. What part was it? I don't know. What brand tube was it? I don't remember. But I do recall the photos showing it apart and the component smoked.

    I know that's not super helpful and it may or may not apply. Hopefully you can go back a few years and find it. I don't remember who was in the conversation but it would not surprise me if Rodne Gold was part of the conversation. It's been at least 5 years ago, probably closer to 10 now.

    I guess the point is that it's possible it's just a component which would explain the sudden stop. If I remember right (it was a long time ago), the item that went bad was smoked so it was quite obvious when looking at the board which was inside the tube's housing.
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  3. #3
    I remember that story, I believe the part(s)? were capacitors- Thing about capacitors is there's 2 of them in an RF laser, even if one goes the laser will still fire at half power. The theory goes that once one goes the other soon follows, but my BIL has shot a hole in that theory, as his 40 tube blew a capacitor about the same time that thread appeared, and he's been using the thing daily with no issues other than it is indeed running at half power... I know the Synrad tubes have 4 or 5 lights on them near the connector, not sure what they're supposed to indicate, just wondering John, if you've checked those out ?
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  4. #4
    Quote Originally Posted by John J Wang View Post
    We have an older ULS-M300 35Watt laser engraver. The original tube lasted almost 8 years, but the replacement tube abruptly stopped working after 2~3 year of very limited usage.

    that may have been the problem. As it was explained to me, the laser must be run to ensure the electrons remain excitable. I've run my tubes for 5+ years. One was unused for about a year and when I went to use it, it had fully discharged. If you have a ULS dealer near you, perhaps you can negotiate for a loaner to test before a replacement to put your mind at ease. Shipping it back and forth would be cheaper than a service call.
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