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Thread: Question about mA Meter on Chinese Laser (With Video)

  1. #1
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    Question about mA Meter on Chinese Laser (With Video)

    I just installed a mA meter on my Chinese laser, but I'm not getting much of a reading from it. It's all explained in the video. If I fire the laser at 20-29%, it'll register up to 5mA, but only when the tube makes this high pitched, faint squealing noise. No noise, no reading. Also, if I fire at 30% and up, no reading. The laser fires and engraves as low as 20%. If I go below 20% on power, it's will fire, but it is extremely faint. I get a movement of the mA meter as low as 13% power. I feel like the issue is the tube itself, but I wanted to get the opinion of you guys who are more familiar with the Chinese machines.

    Here's the video - Yes the garage is a mess:
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  2. #2
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    There is a piece of engraved wood inside the machine, did that machine do it?
    Was your machine engraving before you installed the meter?
    If your machine works but doesn't give a reading, do you think you have it wired backwards?
    Scott
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  3. #3
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    Yeah, the machine engraved the wood. It's been engraving OK, but it's not very good with cutting. I struggle to cut through 1/8" plywood with it. I don't know if that's because of the tube or the super cheap optics, though.

    I don't *think* the meter is wired backwards. I've read that if it were wired backwards, the needle would move down instead of up when the laser fires.
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  4. #4
    you say its hard to cut 1/8 plywood.several things could cause this
    1. is it a true 50 watt laser and not a 40 or 35 watt with a max zap of 50.what the length of your tube?
    2. Exact focus for good cutting
    3. what lens are you using 1.5",,2.0 ect4
    4. clean lens and mirrors very important to get the best cutting.
    5 what speed and power settings are you using.you have to go slow with almost full power. remember the ply has glue and plugs in it, makes it difficult to cut sometime.
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  5. #5
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    you say its hard to cut 1/8 plywood.several things could cause this
    1. is it a true 50 watt laser and not a 40 or 35 watt with a max zap of 50.what the length of your tube?
    It's a 50. It's 1050mm long - advertised as a 60 watt.
    2. Exact focus for good cutting
    I've tried different focus levels to make sure focus isn't the issue.
    3. what lens are you using 1.5",,2.0 ect4
    2.0"
    4. clean lens and mirrors very important to get the best cutting.
    The mirrors and lens are all spotless, but the mirrors are the low quality silver ones.
    5 what speed and power settings are you using.you have to go slow with almost full power. remember the ply has glue and plugs in it, makes it difficult to cut sometime.
    I've been running the power at 85 to avoid overdriving the tube. For speed - I've gone as low as 2mm/sec. At that speed, it just chars the cut and never gets all the way through. To get it to cut all the way through, I have to set the power to 85, speed to 10mm/sec, and go over it about 20 times. Even then it doesn't always cut all the way through. It doesn't even cut through 1/8" cork sheeting. It just cuts about 3/4 of the way through cork and burns it to death. But at the same time, I can get good depth when engraving so I don't know that it's necessarily an overall power issue for cutting. Seems almost like a beam profile issue. I'm upgrading the optics sometime soon either way.
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  6. #6
    Looks like it then.
    If the Help and advice you received here was of any VALUE to you PLEASE! Become a Contributor
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  7. #7
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    Quote Originally Posted by Brian Leavitt View Post
    I've tried different focus levels to make sure focus isn't the issue.
    Have you tried a ramp test to see where your focus should be or are you using a shotgun approach?

  8. #8
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    I did not watch the entire too long video, is your mA meter in the negative lead of the tube?

    If you set your power level to 90% what does the mA meter read? If its not 20 +/- 3 or so that is one problem. You should be able to cut 1/8 plywood , with a 40 watt tube.

    1050 mm tube is more than likely a 40 watt peak tube when it was new. No such thing as a 50 watt tube either 40 or 60 and a 60 is 1200 mm long.
    Cheap optics and dirty mirrors can be a issue but right now you have power problems.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  9. #9
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    Quote Originally Posted by Gary Hair View Post
    Have you tried a ramp test to see where your focus should be or are you using a shotgun approach?
    Yeah I've done the ramp test, the results of which I use for typical engraving and cutting. I've tried closre and farther focal distances recently to make sure focus isn't the issue.
    Last edited by Brian Leavitt; 12-01-2016 at 12:26 PM.
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  10. #10
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    is your mA meter in the negative lead of the tube?
    Yes

    If you set your power level to 90% what does the mA meter read? If its not 20 +/- 3 or so that is one problem. You should be able to cut 1/8 plywood , with a 40 watt tube.
    Barely moves at all - pretty much stays at zero. The only time I get an actual reading is when I run it at 29% power or less AND the tube makes a high pitched squealing noise. It engraves and cuts whether I get a reading on the mA meter or not, and whether it makes the noise or not.
    4 - Q1 converted New Hermes C2000's
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  11. #11
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    It sounds like you may have a tube or power supply problem, since you are showing very little current "flow". You should check all electrical connections (using appropriate precautions).
    You might also check to see if you have a Max power setting in the software that is set too low.??
    Scott
    Rabbit Laser RL-60-1290, Rotary attachment, Corel Draw x6, Bobcad Ver 27
    Juki-LU 2810-7, Juki 1900 AHS, Juki LU-1508, Juki LH-3188-7, Juki LH 1182
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  12. #12
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    I think you have the leads backwards on the meter

  13. #13
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    And this is your new eBay laser? Hmmm well check your power supply, find a You Tube video and plan on either/or new tube and PS? Meter backwards the needle would move backward, something to try.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  14. #14
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    I've had it probably 15 months or so. I knew when I bought it the tube and/or power supply probably wouldn't last long, so it wouldn't surprise me if either were dying. I don't have a way to test the output voltage of the power supply.

    I'll reverse the wires on the meter and pulse it at low power to see what happens. Wouldn't hurt anyways.
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  15. #15
    Dude quick messing around

    Trouble shooting Logic 101.
    Remove the mA meter and return the laser to stock.

    Do you still have a problem? Yes or No

    And go from there.
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