1. #1
    Hi, can anyone help ? The potentiometer on my Chinese 40w laser normally operates in a linear fashion working from 0-14. 14 is the maximum power. It now only produces any power between 1 and 3. 2 appears to be producing full power on the laser and rapidly tapers off in either direction.
    As a complete electronic ignoramus, I am assuming that the pot is faulty. However the specification is illegible, so can any one tell me what the correct specification for the pot is please. I thought it was a 5k 2w, but I am not sure. Otherwise could something else be causing my problem?
    (complete newbie to forums so apologies if I am in the wrong place etc.)

  2. #2
    I presume that, if you can say the markings are illegible, you can get to the pot. Is it possible to measure the resistance at the ends and check that the resistance changes smoothly from zero to max when you meter across the end and the middle and operate the knob. (power off, of course).

    If it is the pot, then the symptoms you describe are strange. Normally I would expect a burnt or worn track where the wiper made poor contact, or some sort of short.

    Note that other components could cloud the results, so it would be best to check the pot when it is out of the circuit.

    It would help if you could tell us the make and model of the laser.

    Cheers,

    'Doc'

  3. #3
    Quote Originally Posted by andyisko View Post
    Hi, can anyone help ? The potentiometer on my Chinese 40w laser normally operates in a linear fashion working from 0-14. 14 is the maximum power. It now only produces any power between 1 and 3. 2 appears to be producing full power on the laser and rapidly tapers off in either direction.
    As a complete electronic ignoramus, I am assuming that the pot is faulty. However the specification is illegible, so can any one tell me what the correct specification for the pot is please. I thought it was a 5k 2w, but I am not sure. Otherwise could something else be causing my problem?
    (complete newbie to forums so apologies if I am in the wrong place etc.)

  4. #4
    Quote Originally Posted by cropwell View Post
    I presume that, if you can say the markings are illegible, you can get to the pot. Is it possible to measure the resistance at the ends and check that the resistance changes smoothly from zero to max when you meter across the end and the middle and operate the knob. (power off, of course).

    If it is the pot, then the symptoms you describe are strange. Normally I would expect a burnt or worn track where the wiper made poor contact, or some sort of short.

    Note that other components could cloud the results, so it would be best to check the pot when it is out of the circuit.

    It would help if you could tell us the make and model of the laser.

    Cheers,

    'Doc'

  5. #5
    Thanks for the quick reply. I have discovered that the pot is a 2 watt 1k pot. However, I tried a similar pot which reacted in the same way, so I am beginning to think the problem may be with the power supply unit. If that is the case then I am totally lost. The laser cutter is a Chinese k40 purchased via eBay, other than that I don't have a makers name.

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