UK- what cheap things can I buy that have bagel shaped transformers that whine?

I'm in the UK. What cheap things can I buy that have bagel shaped transformers that whine?

The reason, is I want to practice silencing them, with liquid epoxy.

These are the kind of transformers i'm talking about

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But I want to practice on something cheap.

Reply to
jameshanley39
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Are you sure its just the torroids/coils that are whining ? Copal varnish was the norm for laminated iron cores that rattled, it is less rigid than epoxy which may be relevant

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

What exactly are you up to ?

Whining may indicate poor design, inferior materials or sloppy construction here.

Graham

Reply to
Eeyore

Or a fault. The image shows torroidal chokes, not transformers, and it's fairly rare for them to whine anyway, unless there is a problem. These items can actually run quite hot in normal use, so anything used to quiet them needs to take this into account. As Graham says, what exactly are you looking to do here ? I could suggest any number of cheapo switch mode power supplies that utilise these chokes, but you could buy a hundred, and not get one that needs attention for whining. Maplin sell the actual chokes - or at least they did when I last bought some - so it might be worth just buying some, and then seeing if you can persuade them to rattle by hitting them with some high level audio from a signal generator, or dare I suggest, from an amplifier, but with the caveat that you would need to be careful not to load the amp too hard with the unknown impedance that you would be presenting to it with one of these chokes. Once you've found a mechanical resonance frequency where you can get the windings whistling, you can experiment away. I would have thought that one of the liquid silicone rubber coatings may be more effective at quietning a torroidal choke.

Arfa

Reply to
Arfa Daily

people have aksed me

what am i up to am I sure it's the coils are these "torroidal chokes" or transformers I have to take into account the heat these things produce.. why not get ac dc adaptors ..

Well.. I want a fanless computer, it's an ideal, but i'd like it. And I don't like things that make a high pitched whining noise either. Some years ago the only option was a VIA machine. Now, there are fanless components, but i'm not convinced how long a regular MBRD would last fanless. There are "voltage regulators" on the mbrd that need cooling, i'd need a heatsink for them. And i'm not sure how reliable the fanless power uspplies are.

A VIA system is cheap. I built one years ago anyway. But there was one problem.

The Fanless power supply card made a high pitched noise. Just like some TVs do. Just like some cheap ACDC adaptors do. That power supply card was made by a company called Morex. There was another competitor that made one but it had the same problem. I contacted Morex, and they said it was because the transformers were not made with ferrite. And to do so would be more expensive and they don't do it.

I have no electronics background. But getting some liquid epoxy and filling up a bagel shaped transformer, or thing that looks like a transformer. That I understand! Epoxy I think conducts heat.

The morex power supply card (I bought it from linitx), has gone walkies, and the newer versions are probably not the same. THey may whine, they may not whine. Most shops they can't hear the whine. If they could then they I doubt they'd be able to use it!!

I did buy a cheap AC-DC adaptor and it whined, so I took the opportunity to try to silence it. That didn't work out. See the transformer second from the left second row from the back.

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That's what it had. So, I couldn't get liquid epoxy into it if I tried. I tried unsoldering it but it wasn't coming out unless I snapped the board.

So I resigned my hope to merely being able to silence bagel shaped transformers. Ones that I can get to.

I remember my old morex power supply card had them.

It'd be nice if I had some unviersal way to silence those. e.g. liquid epoxy. I need some cheap way of trying it.

As mentioned, the ACDC adaptor thing didn't work out. It whined but was in a housing.

I'm sure in the case of the morex power supply card , it was the transformer that was whining. I managed to bare the nightmare of putting my ear near it to find the culprit. The morex technicians thought it was the transformers too, and admitted they whine!

Reply to
jameshanley39

??? Use a piece of 1/8" or larger plastic or rubber tubing. Stick one end in your ear and use the other end to identify the noise source. Automotive vacuum or windshield washer tubing are cheap, easy to find, and is sold by the foot.

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Reply to
Michael A. Terrell

Some of those items in the picture are transformers, some are chokes. The one that you point out looks like a tranny, but that's by the by now that we know what you are doing, anyway. I think that the only way you are going to stop rigid ferrite cores from rattling at their drive frequency, is to muffle them with something soft, which may or may not affect the temperature that they run at, depending on whether that's hot in the first place.

There are liquid - or at least semi-liquid - silicone rubber compounds available, with non corrosive properties, designed for 'soft potting' of electronic sub assemblies. I used to use one made by Dow Corning for encapsulating a counter board that had to work in very hostile and moist conditions. You could try surrounding any offending transformers with a little cardboard 'wall', and then filling this with the rubber compound. I don't think that much whine would escape that, but you might still be contending with vibrations transmitted directly into the PCB via the core touching the board, or even via the pins. Go have a look at

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where there are lots of them with pdf data sheets

Arfa

Reply to
Arfa Daily

ok.. i'll try some of those - what look like liquid compounds - at your link. And i'll try the liquid epoxy too.

But where will I find a cheap product with bagel shaped whining transformers or chokes..

I don't have an electronics background. Is it feasible for me to buy them separately, connect a battery to them and get them running so I can try.. ?

Is there any place where I could get instruction on how or any book or website with an example ?

I'd even consider paying an electrician geek in the UK, as long as it's not too many hours. If they've got the expertise. Though i'd like to know how to do it myself. If I could ask an electronics geek and as part of that, learn how to do it myself that'd be ideal..

Reply to
jameshanley39

Well, as I said, Maplin stores sell those toroidal chokes for constructors who want to put together their own chip-based switching power supplies.

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If you have an old hifi or amplifier kicking about, you could connect one of these across the output, and hit it with some music - I guess that violin or piano might be good. But I would caution you to start with the volume right down, and only wind it up enough to get the choke singing with the music, because it will represent an unknown impedance. Any decent amp would protect itself against any damage that might ensue if the impedance happened to be very low, but obviously, I can't guarantee that,

Another source for those chokes would be your local computer repair shop, or a TV repair shop if you have one around you. Either of those will have scrap switch mode power supplies coming out of their ears, which I'm sure they would be happy for you to relieve them of. You will find plenty of coils and chokes on those that you can remove to experiment with.

Arfa

Reply to
Arfa Daily

i'm more of a computer techie than electronics geek. I see from the picture at the link, the "choke" has 2 metal wires coming from it.

Now, if I want to connect that to a piano or a violin.

It sounds like I don't need to connect a battery to it. I thought I would have had to!

Would I be touching both prongs against violin strings?

I notice a piano has metal rods in it that vibrate. I guess the same thing applies.

The chokes or transformers make their unbearable high pitched noise (so very high frequencies). I can't imagine that somehow connecting a piano or violin to it would get it at that high pitched unbearable noise which I recognise and want to silence. I'd have to trust in the assumption that if I can get the choke or transformer singing at all, and then silence it, then it's silenced at any frequency, including that unbearable one. Is that a fair assumption? Maybe an "amplifer" would let me choose frequencies including that unbearable one. Would it have rods to touch the prongs of the choke against?

my other concern is that those rods on the piano look like they might be quite delicate. I wouldn't want to mess up the piano's sound. Or drop a choke in the piano! Similarly, I haven't seen people with violins plucking strings with their fingers, they sort of stroke the strings with a rod, so, those strings may be very delicate too. I'm wondering about the amplifier option. Is there a cheap amplifier that can reach the unbearable frequency, and does it have rods?!!

(the unbearable frequency must be related to AC, so it's probably a frequency known to electronics geeks, you prob know it)

thanks

Reply to
jameshanley39

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