Cheap ultrasonic cleaner doesn’t work anymore
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Re: Cheap ultrasonic cleaner doesn't work anymore
There are only a few components, The ic drives the two fets, they switch on and off at around 40khz. The output drives the piezo. the output signal goes through the transformer winding (the one with the resistor in parallel) the other winding provides a small sample of that signal back to the ic via the control. It does look like the control is used to fine adjust the frequency.
Check C20 & c22, and the 3 resistors next to the control, check the control also.Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
There are only a few components, The ic drives the two fets, they switch on and off at around 40khz. The output drives the piezo. the output signal goes through the transformer winding (the one with the resistor in parallel) the other winding provides a small sample of that signal back to the ic via the control. It does look like the control is used to fine adjust the frequency.
Check C20 & c22, and the 3 resistors next to the control, check the control also.Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
I'm wondering if it's an issue with the control side where you set the duration you want it to run. I noticed sometimes not always the counter will glitch when counting down. But idk if that's related to the piezo not being turned on causing it to behave that way.
Anyway to turn the circuit on for testing without the display control?Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
The ultrasonic portion of the circuit is turned on or off by the relay, thats it. The two elec. caps (near D10) along with D10, D1, & C10 form a voltage double (328vdc) that feeds R3 which connects to one contact of the relay, the other contact connects to the (328V) in the schematic.
The 4 diodes below the relay are the bridge for the low voltage, C5, R4, C7 are the filter. C7+ supplies the relay coil, Q1 switches the coil on or off from the top board.
D13 is likely a zener which is on the base of Q2 which is used as a regulator for the (5v?) to the top timer ic/circuit.Last edited by R_J; 03-10-2020, 09:56 PM.Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
It worked before, so something changed. I see the ends of the wires (under the glue) on the piezo, look black,maybe they are no longer attached to the transducer.
You might be able to check if there is any ac voltage across the transducer. Check if there is any AC voltage across C16 when you turn on the unit. The frequence will be high (40khz) so your meter might not see it. I would think you should be able to see a couple hundred volts ACLast edited by R_J; 03-11-2020, 11:10 AM.Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
It worked before, so something changed. I see the ends of the wires (under the glue) on the piezo, look black,maybe they are no longer attached to the transducer.
You might be able to check if there is any ac voltage across the transducer. Check if there is any AC voltage across C16 when you turn on the unit. The frequence will be high (40khz) so your meter might not see it. I would think you should be able to see a couple hundred volts ACLast edited by caphair; 03-11-2020, 03:52 PM.Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
The melting point of silver solder is way too high, Use regular solder and be very quick and do not keep the iron in one spot or you will damage the piezoAttached FilesLast edited by R_J; 03-11-2020, 10:02 PM.Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
Thanks for the info. As I was trying there was a square tab on the side that the wire was soldered you and it broke off. Not sure if this was the original fault and when trying to fix it made it come off completely. Can this be fixed?Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
Not fixable at this point?Comment
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Re: Cheap ultrasonic cleaner doesn't work anymore
I don't know how you you could even get at the bottom to resolder the connection, the top is also bad, It seems like the glue did most of the damage to the piezo. You can likely solder the top wire to a different spot to make a proper connection but thats not going to help if the bottom is not connected.Last edited by R_J; 03-14-2020, 05:13 PM.Comment
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