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The Grundig UC6620 ultrasonic cleaner is a 35W cheap device with a lot of failure points.
Faults I had to repair in my unit were:
- A broken transducer
- Shorted driver transistors (IRF830 500V NFET)
- Shorted rectification diodes from the second discrete rectifier in the circuit, that's before the driver
- An open 0.1 Ohm resistor coupling the rectified voltage over to the driver transistors. The damage was not visible!
|Fault description||image of Fault|
|Fractured/broken ceramic piezo electric transducer|
|Open circuit resistor coupling the rectified voltage to the driver|
|The main PCB where the main driver transistors are very prone
to dying. The Driver chip seems to be very robust as it retained
no damage during a lot of failing attempts at restarting.
output can go short too. They're 1N4007 standard diodes.
|The output capacitance was adjusted with this smaller foil
cap, parallel to the transducer, because it has a larger
capacitance than the original.