Olympic-sized ultrasonic bath

[BurningTantalum]

Recently I spotted a gigantic ultrasonic cleaning bath at an auction. The guide price was several hundred dollars and I wasn't too certain about the reaction from 'The Gate Guardian' if I arrived home with it. The price dropped over the weeks until last week I found that a friend had nailed it for $10. He wanted to strip it for the pipework, Grundfos pumps and heaters etc, but I persuaded him to deliver the remnants to me which he did.
I have one of the tanks, 1270x670x150mm, complete with 12 parallel-connected transducers, and two complete drive PCBs. One appears to be unused and both are suffering from some corrosion. The maker is Hilbre Ultrasonics, possibly UK and now HiSonic Ltd, model FMG600.
The drive part consists of six parallel-connected TO3 NPN bipolars with emitter resistors; I cannot find any details of the type: 2H0U8. The manufacturer's logo is a squared ES.
One transistor has been replaced with a BU208 and has probably worked with this.
Q: Anyone come across the 2H0U8 ?
Q: What is the best way to clean up the corrosion. The picture shows the very worst of it; it is much lighter on the rest of the board.
I will repair some of the corroded component leads and fire up the unit, but would like to clean the PCBs if all is well. Would it be best to remove all components and scrub the track back to copper and re-populate ?
Regards,  BT

[T3sl4co1l]

Eww...

I'd say, give it a wire brushing (preferably with a fine steel or coarse brass brush), and... if there's any meat left under the worst of it, try to patch over with some globby solder and extra wire.  The rest of it should probably be re-tinned to protect what copper remains, and to refresh the solder layer, since I see greenish haze over much of it.

Transistor is a wildcard.  It's likely anything 2N3055 sized would work, consistent with whatever the voltage and current ratings of this thing actually are.  Hmm, BU208 is high voltage; is that line powered?  Must be some serious ultrasonic action in there... I'd guess 100W minimum, but beyond that... who knows how powerful it is?

Tim

[SeanB]

BU208 or a BU508 ( not the D versions, which have the integrated diode) are pretty common as high power ultrasonic drive transistors, you basically have a TV line output stage there with a 20-40kHz or so frequency of operation. Cheap, rugged and work on 160VDC ( rectified US 115VAC mains) quite well.

[LabSpokane]

To kill the corrosion, try this:

http://www.corrosionx.com/corrosionx-aviation.html

It's the closest thing to a miracle in a can for what ails your board.

[pickle9000]

Make sure you have good pics of the pcb. I wouldn't remove anything unless needed. Brush of the rusty bits firs and make sure the board is bone dry. That way you can blow off with compressed (canned) air and keep it from sticking to any coatings. If you have given it a wash with iso then let it dry well before brushing off.

Next comes a wash with iso and get off everything possible.

If the transformer is paper wound then remove it and clean it by itself (no iso just brush it off and spray with a bit of conformal coating). Old transformers can be picky to deal with take measurements before power up just in case.

[BurningTantalum]

Thanks for all the info.
 Labspokane - My contacts at Rolls Royce turbines, the RAF and South African Airways have all retired, and the fluid looks a bit expensive, so it will have to be the brass brush in the Dremel !
Teslacoil - The output IS line powered, at 240V. I was just curious as I had not come across anything like that type number before, and could find no reference anywhere. The devices are probably not too critical apart from the Vceo of 1500V, plus I have 5 spares on the second PCB.
I am in the process of finding a valve/tap/spigot and two threaded bungs to seal the outlets in the tank and I will give it a whirl. I suppose I could put the spare PCB in the tank to clean it..!
 I have no idea how 'fierce' this unit will be - my only other experience is with my titchy jewellery cleaner that can just contain a Walbro carb from my strimmer/whippersnipper/weedwhacker.
Thanks again,  BT

[SeanB]

You can drop a carb that is a blob of gunk in it, turn on the power for a half minute then pull the white alloy casting out of the now dirty water and soap/ alcohol mixture. It will remove any paint and any rubber seals and pretty much destroy  any plastic items ( and any thin alloy as well) with prolonged exposure. With that number of transducers and the likely power level of around 200W, it will do serious damage to your hand if placed inside as well. We used one of around half the number of transducers to clean avionics. It would strip off the conformal coat in around 15 seconds and turn the board into fibreglass fluff in 3 minutes. Only coat that survived was the Mesopoulet K epoxy, which would peel off the fluff as a single layer, along with the components and the tracks. Lucky it is a solder through coating.......