The Delta Ultrasonic Cleaner is a mains-powered ultrasonic cleaning tank. It has a stainless steel tank with a plastic lid and on/off controls.
I was given the cleaning tank as a "fix-it" project. The main fuse would blow as soon as the "on" button was pressed.
Closer examination of the PCB revealed that the unit is powered by simply rectifying and smoothing the 240V AC mains. An auxiliary supply operates a relay that connects power to the ultrasonic oscillator, driver transistors and transducer. At this point, I suspected that the driver transistors were faulty.
The two driver transistors, BU406 parts in TO-220 packages, were shorted.
I obtained two replacement transistors, from Farnell, order code 980-1782. They were easy to desolder and replace, with just a normal soldering iron. The transistors were bolted to two fairly large heat-sinks.
Reassembly is the reverse of disassembly.