Ultrasonic cleaner repair

[woodchucker]

We picked up a small to medium sized usa made ultrasonic cleaner from online seller ad of course, the ultrasonic part does not work.

It is 50khz and 60 khz dual frequency with tank heat.

The driver is working but the connection to transducer is bad.

Someone tried to solder it and failed.

Looks like it is attached, only the Flux was holding it, scope had many volts on the solder, zero on the transducer, gentle pull and wire with solder lifted up with wad of Flux in the middle.

Looks like transducer is attached with epoxy, difficult, but not impossible to remove.

Trying to find replacement transducer, most are 40 khz, and are different shape.

There are lots of options, looking for someone who maybe has done this before or knows how to source these things.

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while building glider models there was a time we used stainless steel hollow pushrods. Harris Silver solder worked well to attach stainless to other metals. You might try that over electrical solder. Yes it has an acid based flux.. So use baking soda to clean after. I have used acid successfully numerous times.. contrary to what everyone here says. I did my winch cables.. I just clean it well. 20 some odd years and still going... imagine that.. going against the wisdom and still working.

 

[mcostello]

Sometimes "wisdom" changes daily. Remember don't eat eggs?

 

[tq60]

The solder is fine, must have correct temp and Flux, and be QUICK and GENTLE, the Flux transfers the heat.

But,
DO NOT DO WHAT WE DID ABOVE!!!

Unless you want to blow out your driver!

The tech in me should have known better, but these are magic.

One would assume the surface being a single layer of silver plating that the whole area is same, so making parallel connections should be good, at least it sounds good on paper.

The unit had less power and just barely made stuff on the bottom of the tank move, then it stopped making noise.

No output from driver, looks like the output transistor is blown, replacement on the way.

Went outside to prune trees then the light went off.

What if it matters where the connection is made?

The pizo crystal may be thought of as a big capacitor in relation to ac current flow.

The silver surface must have some resistance as well.

So by having multiple connections to the disc, it may have acted like parallel devices and lowered the impedance somehow and overloaded the driver.

We removed the 3 connections, a bit tough with the epoxy, one removed the plating.

We resoldered the wire next to the first place and epoxied it in place, hopefully it will work.

ONLY ONE CONNECTION TO THE TRANSDUCER!

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[Flyinfool]

Would electrically conductive epoxy instead of solder work in a case like this?

 

[tq60]

The solder is fine.

The transducer had enough energy to knock off the wire, with the film


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