I got a used ultrasonic cleaner with liquid damage for almost nothing and I am trying to repair it. So far I’ve confirmed that the board has a short circuit between live and neutral somewhere after the relay. Also, while reverse engineering it, I noticed something that seems weird. When the relay closes, it adds C3 in parallel to C2, both feeding the logic circuitry.
i think it’d be useful to isolate the issue and get it working again first. the circuit is simple enough you can test almost everything individually.
are those wet logic gates and diodes working correctly? is the logic simple enough you can simply hook the ultrasound up directly to power and have it go?