Ultrasonic cleaner.

[dobbslc]

Mines stopping working, does anyone know how to test the piezoelectric transducers and the driver boards?
It's has 4 50watt transducers and two separate boards but I don't know what readings I should be getting.
Cheers.

 

[AndyStobbs]

The firm that made and repaired mine told me its usually the transistors on the driver side, and that the transducers must be plugged in or the board will be damaged further.

 

[graffian]

I bought mine as a non working one on ebay. The fault was the two output transistors on the ultrasonic generator board were dead.
I fixed it and a few months later it died again, second time the two transistors had gone and a couple of big resistors as well, it's been
fine for five years or so now.
I will look for the transistors, maybe yours takes the same ones, from RS they were about a tenner, I can't remember if that was each
or the pair; but from china they were a fiver for a bag of ten!

I would check the two transistors first.

 

[dobbslc]

Thanks chaps!
Here's a photo of the boards maybe they're the same ones?
Edit: how do I test the transistors?

 

[MoreWellie]

EDIT: I noticed there is a fuse on the board. You have checked that haven't you?

please don't do anything you are not comfortable with

first disconnect everything from the mains and leave it a while for the board to discharge

The transistors are the bits with 3 legs bolted to the heatsinks

You can test them with a meter set to the diode continuity setting

The 3 pins are base collector and emitter and which is which depends on the part number on the transistor. often, but not always, looking from the front it will be base on left, collector in middle and emitter on right

with the transistor disconnected there should be no reading between collector and emitter whichever way round you put the meter, base to collector and base to emitter should read (beep) one way round for the leads but not the other

if you do take them off the heatsinks note how the bits fit in between as the transistor is usually meant to be electrically isolated from the heatsink

 

[eSCHEn]

Also, get a better pic of those transistors up. Something where the lettering and number can be read.

You never know what replacement parts people have

 

[dobbslc]

Thanks . The number on the transistor is J13009-2 I've now Googled it and found that the base is the left leg looking at it from the front so my original assumption that they were faulty could be wrong as I thought the base was the middle leg!
They are still connected so I might pull one out and give it a proper test.
The bloody thing fired up once on one board and one set of transducers when I plugged it in but then wouldn't work again straight after. Hmmm I thought transistors failed completely.
I have found that the cooling fan is knacked though so that might be the cause of the troubles here.... thing is you can't hear it when the machine is working and it looks very clean so maybe it's never worked from new!

People's Republic of China? Pah!

 

[eSCHEn]

Yep whip 'em oot to test properly.

I was sure I had some switching NPNs in a TO220 that would suit but I've rooted about and only have TO92 (too small) and TO247 (too big).

However, they are a fairly recent model (2014) so easily obtainable:

http://uk.rs-online.com/web/c/semic...tors/bipolar-transistors/?searchTerm=FJP13009

A fiver or so with free delivery; should you need them of course

 

[AndyStobbs]

Voltages on the transducers are circa 100v so you might get a tingle if you probe the wrong bits

 

[dobbslc]

Yep whip 'em oot to test properly.

I was sure I had some switching NPNs in a TO220 that would suit but I've rooted about and only have TO92 (too small) and TO247 (too big).

However, they are a fairly recent model (2014) so easily obtainable:

http://uk.rs-online.com/web/c/semic...tors/bipolar-transistors/?searchTerm=FJP13009

A fiver or so with free delivery; should you need them of course

Thanks for looking and for the link I've got a RS shop just down the road so might drift past during work.....

Voltages on the transducers are circa 100v so you might get a tingle if you probe the wrong bits

Already been there
Andy do you know what I should be able to measure on the outputs to the transducers?
I don't even know if they are ac or dc
Thanks again.

 

[AndyStobbs]

As I understand it, they are DC and essentially just switched on and off very rapidly (20kHz comes to mind) this vibrates the molecules in the fluid and literary rips the fluid apart which creates the cleaning effect. You might be able to measure a DC voltage across the transducers, but without a scope you'll only see an average. Some multi meters do have a frequency setting which may be more useful.

 

[dobbslc]

I've got an old oscilloscope my mate gave me years ago to test a Suzuki GSXR CDI unit!
Maybe I'll have a fiddle with that to see what's failed.

 

[AndyStobbs]

If its an automotive scope you'll likely need attenuation or the voltages will kill it.