transformer buzzzz

On Fri, 05 Jan 2007 02:22:05 +0000, ml Has Frothed:

Both my Astron 25 and 35 buzz. I got used to it.

With considerable difficulty.

That does other stuff not mechanical noise.

My suspicion if it's cheap consumer gear is that the transformer has a high working flux that's close to saturation. There's precious little you can do about that other than reduce the input volts.

The other possibility is vibrating laminations because they're a bit loose and there's not a useful lot you can do about that either usually.

Graham

Probably a loose lamination.

First thing would be to determine the cause. Try a clamp on the laminations if you can get to them - a C-clamp. If tightening the laminations together makes it quiet or quieter, the laminations are noisy.

To correct the problem takes some effort. Take it out of the PS, bake it in an oven to thoroughly saturate it with heat and dry it - a few hours at close to 100 C if there's no wax or plastic that will melt - hot if you can, warm if you must. The construction determines how hot you can safely get it - but transformers are usually expected to run hot without failing so they will take some heat.

Once it is hot, suspend it in a can of polyurethane varnish for a half hour or so - the hot transformer will thin the varnish and the cooling air spaces will suck varnish between the laminations and eliminate the buzz. Let it air cure for a few days before putting it back in service.

Loose coil? A wooden shim driven between the coil and core will fix that.

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A quicker less thorough method that may work is to put a cold chisel onto the lam edges and give it a tap.

You can also remount the transformer onto rubber blocks to stop it using the case as a sounding board.

Can also line the interior of the case with cardboard or rubber matting to damp sound

NT

Soak it in shellac and let it dry. Might tighten up some things. Could be a lamination acting like a buzzer or the coil rattling on the iron core.

silly question, a few here suggested coating /soakn' w/varnich or etc

once it's dried does that stuff withstand the temperatures transformers get up to? this is a 24hr on device

i am also not opposed to simply replacing the transformer i am sure it's not cheep but don't know transformer speak buzz wise i know the input/output spec's but what is a 'quite one ' called just a higher quality one? a super laminated one or one with metal casing around the unit? are they transformer firms know to be 'quite'?

i can't add 'insulation' around the case as somone suggested thou i like the idea since it would trap the heat this unit has no fan

i am aware that all the astrons i've seen do buzz this way i just want to make it quite seems a simple experiment and mod

i tried putting the entire unit onto rubber isolators it didn't decrease the sound actually seemd to make it louader a drop there arent' any coils on the ckt board so opening it up i can tell it's just a transformer issue

it's a 25amp cont supply @13.8vdc (120ac)

if soaking it in varnish or equiv would work that would be ok by me i just concerned that the varnish would burn or melt at some future point but i must admit i live in an apt and puting varnish on the stove given how flamable it is creeps me out if it were to flash over i'd be in trouble i'd need a big amout to submerge the transformer big as a softball or more 100c is 212f thats hot

thanks everybody

What I have done in the past is to put the Transformer in the Oven till it gets to the point you need gloves to bring it out. Get it nice and Hot.... Then submerge the Transformer in the Varnish ,after say 5 mins remove and hang to dry.

kip

On Fri, 05 Jan 2007 21:20:16 +0000, ml Has Frothed:

I used mine in my bedroom to power some ham radio gear. I did get used to it after awhile but ultimately replaced it with a Diamond SMPS that is whisper quiet. It does have a cooling fan but it is temperature controlled. Not sure if a coating of varnish would help you. I think the case amplifies the sound so my first choice would be to find some thin rubber foam material with adhesive tape on one side and cover the inside case with it. I wouln't think it would overheat since the heatsink is on the back.

If you get transformer varnish, it should handle the temperature quite well. That's what it's designed to do. One suggestion that I don't remember anyone making... If the transformer has screws or bolts holding the whole assembly together, make sure that the nuts are securely tightened. That will tighten any loose laminations. I've cured a large number of buzzing transformers this way.

Cheers!!!!

are

Hi...

A further thought if I may. Don't just tighten them up, but rather experiment a bit with the degree of tightness and combinations on all four bolts. Play with them (safely) a bit, while it's powered up.

Take care.

Ken

If you get to the point of replacing the transformer, I would suggest going for a toroidal type. They tend to be physically smaller and lighter than an E-I lamination tranny for the same VA rating, and they are invariably very quiet. Whilst not ' cheap ', a suitable replacement should not be an "arm and a leg" job either.

Arfa

Careful use of superglue on the laminations may help! It certainly works on smaller ones!

Great idea.

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