Menticol
Active Member
Hello guys! Long time no see! I wish you a great year.
I come to you with another electronic enigma. This time is a Chinese ultra sound sealing machine, used for plastic clothing.
Before explaining the symptoms, here's my guess of how it works and what I've done:
First there's a ultra-sound transducer attached to a metallic plate. The cloth rests over the plate, and is firmly pressed against it by a pneumatically actuated roller. The roller is coupled to an electric motor, to make the cloth advance as the roller spins.
Now the part of interest. There's an electrical box that include control switches, an ampere meter, and the PCBs.
Inside the box there are two boards, one that I call "control" and "power". Control generates high frequency pulses. It also performs other machine functions like controlling the roller rotation motor, the nematic valve, etc.
Now the "Power" board is a transistor bank. A total of 10 x 2C5589 transistors in parallel, driven by the control board.
This power board feed various step up transformers located below, a capacitor bank, a very ugly hand wound coil. I guess someone had attempted to badly repair it.
The output of this circuitry feeds the ultra-sound transducer at the beginning of the post.
Well, recently the machine failed. The main fuse blew up, so I traced the fault to the transistor bank. Since these transistors are hard to get (none on digikey, mouser, just Aliexpress chinese fakes) we bought three new boards from the manufacturer (the manufacturer is not willing to send a technician, so we are on our own).
Since I have no service manual I compared the values from the components on another working machine. The impedance of the transformers is the same, nothing is shorted or open.
Believing that nothing else was wrong, I decided to power up the machine and operate the ultrasound. A loud buzzing noise came from the electrical box every time the ultrasound kicks in. The ampere meter goes up to 5A (the normal working rating is 1). No smell or heat is detected.
Thinking that maybe one of the capacitors was damaged, I checked each one. All of them look good.
Tried disconnecting the transducer (to see if it was the problem). Even without load the noise remained.
Tried disconnecting the switching board from the transformers and the noise went away. But well, without the transformers the machine is a big paperweight!
I also don't know what this component is
The Chinese manual mentions that the output frequency should be adjusted (I assume with a trim pot on the control board). But do you think that mismatched frequency could result on high power consumption? I do prefer to ask you before starting to play with the settings.
Please, if you have experience with this machines or can give me some light about the route to follow, it will be extremely appreciated.
Best Regards
Felipe
I come to you with another electronic enigma. This time is a Chinese ultra sound sealing machine, used for plastic clothing.
Before explaining the symptoms, here's my guess of how it works and what I've done:
First there's a ultra-sound transducer attached to a metallic plate. The cloth rests over the plate, and is firmly pressed against it by a pneumatically actuated roller. The roller is coupled to an electric motor, to make the cloth advance as the roller spins.
Now the part of interest. There's an electrical box that include control switches, an ampere meter, and the PCBs.
Inside the box there are two boards, one that I call "control" and "power". Control generates high frequency pulses. It also performs other machine functions like controlling the roller rotation motor, the nematic valve, etc.
Now the "Power" board is a transistor bank. A total of 10 x 2C5589 transistors in parallel, driven by the control board.
This power board feed various step up transformers located below, a capacitor bank, a very ugly hand wound coil. I guess someone had attempted to badly repair it.
The output of this circuitry feeds the ultra-sound transducer at the beginning of the post.
Well, recently the machine failed. The main fuse blew up, so I traced the fault to the transistor bank. Since these transistors are hard to get (none on digikey, mouser, just Aliexpress chinese fakes) we bought three new boards from the manufacturer (the manufacturer is not willing to send a technician, so we are on our own).
Since I have no service manual I compared the values from the components on another working machine. The impedance of the transformers is the same, nothing is shorted or open.
Believing that nothing else was wrong, I decided to power up the machine and operate the ultrasound. A loud buzzing noise came from the electrical box every time the ultrasound kicks in. The ampere meter goes up to 5A (the normal working rating is 1). No smell or heat is detected.
Thinking that maybe one of the capacitors was damaged, I checked each one. All of them look good.
Tried disconnecting the transducer (to see if it was the problem). Even without load the noise remained.
Tried disconnecting the switching board from the transformers and the noise went away. But well, without the transformers the machine is a big paperweight!
I also don't know what this component is
The Chinese manual mentions that the output frequency should be adjusted (I assume with a trim pot on the control board). But do you think that mismatched frequency could result on high power consumption? I do prefer to ask you before starting to play with the settings.
Please, if you have experience with this machines or can give me some light about the route to follow, it will be extremely appreciated.
Best Regards
Felipe
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