Ultrasonic cleaner repair - скачать в хорошем качестве

Ultrasonic cleaner repair -

Diagnosing and repairing my failed ultrasonic cleaner! Expand this section for details and chapters. This is a cheap "Delta GT-7810A" unit that is several years old, and recently failed while in use. It appears the basic principles of the circuit in this may be similar to many other cheap ultrasonic cleaners, so repairs to those may be similar even if they are different types. I found a video by Marco Reps showing his attempts to repair a rather different ultrasonic cleaner - and the partial circuit he came up with shows the principle of how these work:    • Failed: Ultrasonic Cleaner Repair   The triple wound transformer (toroid in mine) has one winding, the smallest, in series with the ultrasonic transducer connection. The other two windings feed the emitter-base circuits of the upper & lower power transistors. When one or the other transistor switches on, the current flow through the feedback transformer locks that transistor on and the other off; once the transducer reaches its limit with that polarity and starts to rebound in its oscillation cycle, the current through it stops and the transformer flux collapses, causing the first transistor to be switched off and the other switched on, so the transducer is always driven in the appropriate direction and at its own resonant frequency - there is no separate oscillator! A neat circuit, which may well have worked fine for years, IF the original transistors had just been rated for an adequate voltage - 200V transistors operating on UK 230/240V mains (with a peak of around 340 volts) do not seem like a combination for long term reliability! The transistors I used for the replacements were MJE18008E, which are rated 8A and 450V. 00:00:00 Intro and disassembly 00:05:15 Examination, fuse test 00:07:30 Fuse replacement 00:14:30 More components tests 00:19:00 Power on - was it just the fuse?? 00:24:30 Test with water fill - fail! 00:27:00 PCB removal 00:28:30 Circuit evaluation 00:32:30 Transistor tests 00:35:10 Fitting new transistors 00:42:40 Fuse replacement 00:45:35 Re-assembly for testing 00:46:30 Add water, and... 00:47:00 It works! 00:47:20 Two days later, still going strong! 00:48:00 Thanks for watching.