Connect with us

Anyone familiar with ultrasonic generators?

Discussion in 'Troubleshooting and Repair' started by soldersplatter, May 30, 2013.

Scroll to continue with content
  1. soldersplatter

    soldersplatter

    2
    0
    May 30, 2013
    Anyone familiar with ultrasonic generators? I'm hoping someone here knows which components typically fail inside the generator.

    These 20kHz generators are rather basic Chinese units (see pictures) used for welding nonwoven plastic (basically thin plastic fabric). I have a good/working unit and a bad/failing unit so in theory I should be able to compare good versus bad components. Both sets of converters and horns are fine since the good generator can drive both sets.

    Any constructive input is appreciated.

    Also, if there's a better forum to ask this question please let me know


    FYI - I'm no electronics expert: I have previously monkeyed with picBasic and 16f88 chips but that's about it.

    [​IMG]

    [​IMG]

    [​IMG]
     
  2. shrtrnd

    shrtrnd

    3,734
    478
    Jan 15, 2010
    Well, is it just 'not working', or have you got some symptoms?
    Typically, you start with the power supply (check voltage outputs), and work your
    way through the circuits).
    Do you have a voltmeter? Does it light-up when you turn it on? Did you check the fuse?
    Do you see any physically burned components or damage that might isolate the problem?
     
  3. soldersplatter

    soldersplatter

    2
    0
    May 30, 2013
    Problem located:

    The problem was/is located on the board circled in green below. Swapped in a board from the working generator allowed me to locate the problem. Board is essentially rows of transistors (C4237) and resistors. Now to find the bad transistor.

    shrtrnd - symptom, unit powers up but when hitting the test button the generator wouldn't activate the horn (horn vibrates at 20kHz to melt plastic).

    [​IMG]

    [​IMG]

    [​IMG]
     
  4. shrtrnd

    shrtrnd

    3,734
    478
    Jan 15, 2010
    You sound like you have limited troubleshooting experience.
    If you have VOM (volt ohmeter) or DMM (digital multimeter), the simplest thing you can
    do is to put the meter on the 'OHMS' function (board out of the unit, no power to the board),
    and check the resistance value of each transistor on the good board, compared to the
    bad board.
    Transistors typically have back to back high resistance in one direction, and lower
    resistance in the other direction).
    It's quick and dirty, but in your situation, that's what I'd do.
    The transistors that have radically different resistance (ohm) values on the bad board,
    compared to the good board, will need to be replaced.
    The tube-type shapes and rectangle shapes on the back of the board are all resistors,
    none of them looked burned, so they're probably all ok.
    The transistors you need to check are the black, flat rectangles with the three leads
    in your second picture (bolted to the chassis).
    Good luck, hope it's your only problem with the defective unit.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-