OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Ultrasonic cleaner project.

Ok, Trev, Thanks, I will do some measurements and let you know.
It maybe the way I have attached the tranducers to the tank. they must have good contact, pretty sure that is OK.
All is good, should be able to get it working.

Results of transducer testing:
No connection between the centre (positive) contact and earth when disconnected from the boards output. (as expected)

When transducers are connected to the boards output, there is about 0.3 Ohms to earth. (this doesn't sound right to me).

The outer contacts on the transducers (negative) are connected to earth, very low resistance reading 0.3 Ohms.

I will compare these readings to the new board when it arrives.

I didn't do solder connection to the transducers, as 250 deg C max is recommended.
I was going to use heat sinks and solder them, but ended up connecting them with small nuts and bolts.

What is the reading to earth at the board without the transducers connected Mark? Given there is an earthed contact on the transducers, it seems likely to me that removing the basket with the circuit active may have caused an earth loop somewhere. You may have come across an earth loop sometime in audio equipment where too many earths can cause a loud hum in the system. An earth loop can cause quite high currents to flow which may have blown the fuse/board components.

Trev, The board is short to earth.
Cant get back to this for a few days, Thanks for lending your experience to this.

Without knowing for sure the circuit configuration it sounds like the output semiconductors have blown. If they have, and they blew due to a change in current in the circuit due somehow to removing the basket, I'm guessing they are probably FETs which are very prone to that type of failure.
(Don't know your background but in case it isn't in electronics as such, FET is Field Effect Transistor.)

Thanks Trev,
This where it is at:
supplier sent new board & parts for cost of postage.
I replaced the board and ran it for 5 mins, no problems, with tank full of water.
When I fitted the lid with the fan.
The card failed again, no output.

The heat sink where extremely hot, lid on or off.

I then replaced the failed components & disconnected one of the transducers.
I have been running it for durations of 30 mins now, with no problems.

I also added pieces of additional heat sink to each switching device, using screws and transfer paste.

My conclusion,
This board will only power one transducer.
Don't put it in a small box, even if you have a fan.
Heat sinks get too hot causing switching devices, transistors, what ever they are & diodes D4 & D5, fuse to fail.

Do the transistors and diodes have numbers on them Mark? It may be possible to replace them with higher rated ones of the same type but you need to know what the specs are of the originals first. A lot of manufacturers will remove the numbers so that people cannot easily copy their design.

Thanks,
I will buy some to have a spare board on hand.

Failed diodes D4 & D5 (FR15 with RG underneath)
Failed Transistors / FETs Q1 & Q2 (brand name is a lower case f, the numeral 6 in the centre, K41 with J1 3007-2 underneath)
Guess I should try to find components with a higher heat rating)

I was wondering how you set the fan up Mark. Suck or Blow? And did you put other holes in the case to allow flow through? You should be able to google the part numbers and find the specs on the semi conductors. I figured given how easily the outputs failed they were going to be FET's, notorious for being hypersensitive to any sort of load fluctuation.

Trev, I had the fan above the heat sinks, sucking air out of the box.
I did drill many small holes in the enclosure, enough so that the fan motor wasn't working hard.
I have ditched the fan for now and have the board in a larger box cooling naturally.

I am looking for a board that can supply the 2 x 50W transducers easily.

I was thinking that the ideal enclosure would probably be an old PC power supply, built in fan, many also have a built in on/off switch and have sufficient ventilation to keep a 500 watt power supply cool.
This is the company in England that told me their board is capable of two transducers with a 45 min on cycle.
http://www.ebay.com.au/itm/161668556182?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Hope that helps.

Thanks, great stuff, love the idea.
I'm sure I can find an old CPU to use.