NEY Ultrasonic bath - magic smell

[tmcw]

Does anyone know much about ultrasonic baths?

I got one here at work, a NEY Ultrasonik 2QT/H, was in the trash, lovely smell of "magic smoke" having recently been emitted. Might have been the Engineering Dept that dumped it.

Anyway, the sonic and heating lights on the front come on when plugged in and switched on, but no familiar noise I'd expect (like the sound effects from old Flash Gordon tv series of the 30's).

Opened it up, and see some remains of something that was on the piezoelectric device on the underside of the bath, but not sure what it was, the red wire seems long enough to go where it was originally soldered. And a couple of RIFAs on the mainboard, but they're still intact.

Would there normaly be some component connected where the debris is?

[eccerr0r]

Re: NEY Ultrasonic bath - magic smell

original piezo element should have been coated with a deposited metal on most of the entire surface, appears that part of it has been vaporized or melted away so that's gone - realistically cannot redeposit metal there without specialized tools. You can work with what's left and that's what appears to have been done but no longer balanced with the original circuit.

[R_J]

Re: NEY Ultrasonic bath - magic smell

You can try re-soldering the red wire to the piezo (and clean any carbon off the device) and see if it might work, I would solder it to where there is good plating still left, and only use enough heat to solder it and be quick, too much heat and you may crack the device. Likely the best way would be to replace the piezo device but that is not easy

[tmcw]

Re: NEY Ultrasonic bath - magic smell

Thanks for the replies and insights.

Trying to understand what you mean by no longer balanced with the original circuit. Is it like balancing a tyre, and for the piezoelectric element, they add material to get an even spread of ultrasonic waves within the liquid? Sorry if I sound daft.

And what type of metal do they use as deposition material?

I'll try resoldering the wire later. Yep, I know it's difficult to do on these devices, I've tried replace the buzzer on a cheap multimeter in the past, and learned I would have been better off desoldering the wires from the circuit board, rather than from the buzzer.

I opened up another ultrasonic bath we have in the lab to have a look, and it has two similar elements in it, one is particularly clean, and the other doesn't look too far off the element in the first bath.

[eccerr0r]

Re: NEY Ultrasonic bath - magic smell

not sure what metal it is, it's very low melting point, very close to of lead solder and soldering it will easily destroy the metal. Usually you use silver solder to minimize damage to it. This is because the crystal itself is sensitive to heat.

To make it simpler to understand, depending on your actual circuit, it's like using the electrical properties of the piezeoelectric transducer to oscillate itself. With some of the element destroyed, it still sort of works but the characteristics are different. This is the same as quartz crystals used in oscillators, you mess with the quartz, the frequency changes.

Looks like the circuit at least uses it as a bulk substrate, some use a small fraction of it as a reference to oscillate. It looks like one has this pad but it's all shorted together, probably for more power.