Teardown: Reverse engineering an ultrasonic cleaner

-June 08, 2017

After my ultrasonic cleaner failed after not using it for two years, a teardown was in order. I once fixed a similar unit replacing two high-voltage transistors that drove the ultrasonic transducers. That didn’t work for this unit. I am still troubleshooting the problem. Meanwhile, here is the teardown.

This Fisher Scientific ultrasonic cleaner is made by Branson, the well-known ultrasonic cleaner company. This is a simple stripped-down model that does not have a heater or a timer. While I know that running these units dry may cause the electronics to blow up, that never happened with this unit. It was moved 3000 miles and then sat in a humid Florida garage for two years, and that seemed to kill it.

This model has a 2.5-gallon tank; large enough for my Harley carburetors. It’s also handy for eyeglasses, jewelry, and anything else that needs cleaning. The cruddy scale on the side of the tank is due to the evaporated cleaning solution, as well as the hard water I used in California. I now use distilled water and Branson MC-3 cleaner solution.

The unit has no forced-air cooling. Instead it has these slots on the side, as well as slots in the front and rear, so natural convection can cool the circuit board. Some of the stains were on the unit when I won it on eBay, others got added by proximity to my ferric chloride circuit board etching.

The front of the unit has these unused screw countersinks. Instead of a thru-bolt, the sides attach to this location from blind screws on the inside. The covers appear to be injection molded.

The rear of the unit comes off with four screws. The square nuts are captivated in the side covers, so the injection mold has some expensive slides to allow these features. Don’t forget to put these square nuts back in when you assemble the unit. Don’t let the nuts fall out and get lost in the carpet as you take things apart.

The rear panel has an aluminum plate that holds the EMI (electromagnetic interference) ac input jack, as well as a rubber pass-through for the tank drain pipe. The white label reveals the unit is a Bransonic B5200R. The 1.5A current rating is about right for a 185W unit like this. The red label is a multilingual lawyer-speak warning label.

The inside of the rear cover shows good mold design for an injection-molded part. I would guess the material to be ABS, or an ABS-polycarbonate blend.

The rear aluminum panel holds an EMI filter that keeps conducted electrical noise from passing out of the unit and into your house wiring.

The input EMI filter has a 5A fuse. It takes an hour to figure out that you have to pry this little tab out at the back of the plug recess in order to get the fuse out. This fuse blew after I replaced a 3A internal fuse on the circuit board.

Next: Circuitry

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