Re: Ultrasonic cleaners

On 10/6/2024 4:07 PM, Dave Platt wrote:

In article <66f4d3b5$1$1427964$882e4bbb@reader.netnews.com>,
bitrex  <user@example.net> wrote:
 

Any serious gotchas/unobtainium parts with respect to repairing these
1980s/90s(?) Branson ultrasonic cleaners?
>
<https://d2b3o1qijggx1c.cloudfront.net/full-version-images/1200-Ultrasonic-Cleaner_0.JPG>

  From what limited knowledge I have of them, I suspect that there are probably
two major points of possible failure:
 -  The ultrasonic transducers may have reached end of life (cracked?), or
    de-bonded from the steel tank.
 -  The ultrasonic oscillator may have failed.  These often seem to be
    resonant oscillators (a suitably-chosen C, interacting with
    the L of the transformer) driven from the rectified mains voltage,
    with one or two high-voltage NPN transistors or MOSFETs as the
    switching elements.
 For either of these cases, there are probably suitable generic replacements
available.  The trickiest part might be removing a failed transducer from
the tank, and the securely bonding its replacement (presumably with some sort
of epoxy but I don't know what type).
 A good friend of mine had acquired a Quantrex 125-watt cleaner which wouldn't
sonicate at all.  His testing showed that the two NPN power transistors in the
oscillator were dead... and he wasn't particularly complementary about the
arrangement which held them to the aluminum bar which served as a heat-sink.  They
may just have overheated and cooked, after years of service, or shorted to the
heat-sink and fried themselves.
 The specific parts in question were unobtanium.  I looked around on DigiKey
and found some modern parts which looked like suitable replacements... better
voltage and current and dissipation ratings, similar package, and not
expensive.  I included a few in my next order, and handed them to my friend
along with a couple of suitable-sized mica insulators left over from my
amplifier-building project.  He installed the new parts (with proper
silicone grease), and the cleaner came back to life and makes plenty of
cavitation.
  

Hi, thanks for getting back. The used unit I picked up seems to ultrasound pretty good and passes the aluminum foil test, putting lots of tiny holes in it...it's perhaps not in perfect adjustment but probably will work well enough for my purposes which isn't much more than cleaning various electronic bits, toy train parts, and maybe my girlfriend's jewellery from time to time.
Heater seems bad (can hear relay switching but no heat) but that's probably an easier fix, though I haven't had time to dig into it.