buzzing power transformers

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buzzing power transformers

Postby harry » Sat May 28, 2005 7:57 pm

Hi All..

i was wondering if anybody could tell me whether it is dangerous when a power transformer emits a mechanical buzzing noise.

its happening in my gibson goldtone guitar amp. When i press on the transformer, it doen't buzz as loudly.
I suspect (with limited knowledge) that it buzzes because the windings inside are slightly loose, are the windings encapsulated with melted wax? to stop this?

any technical explanations would be apreciated?

the amps 6months out of warranty, wondering if its a repairable problem, a replacable part (probably cost heaps?$, or one that i should live with (if its not dangerous)

apart from this the amp is fine

thanks again
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Postby Kurt » Sun May 29, 2005 2:06 am

As mentioned in another thread lots of tranformers in my house hum a bit. I was told by a local techie that it can be caused by fluctuations in power supply voltage. I guess the wire expands and contracts alot with fluctuations causing it to heat and cool constantly? The wax potting is only an outer layer which I'm sure helps under normal conditions but maybe not with this much variation in temperature.

All a slightly educated, but mostly wild guess. I'm sure somebody will correct me :)
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Postby chris p » Sun May 29, 2005 9:18 am

Like Kurt, I make no pretense to expertise, but my guitar tech knowledge tells me that pickups are potted (filled with melted wax) to stop them becoming "microphonic" and producing ringing artifacts. It does stop movement of the pickup pieces relative to each other, but don't know if that is your probem. Above all, potting is a fix to the signal path, and generally has no effect on mechanical buzzing.

So when you say the trannie is buzzing, is it a mechanical noise (ie NOT coming through the speaker), a signal noise (ie through the speakers) or both?[/i]
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Re: buzzing power transformers

Postby Linear » Sun May 29, 2005 12:14 pm

I'd speculate that a buzzing mains transformer is a poorly made transformer. There is a fair bit of EMF floating about a mains transformer, a little like a constrained AC electric motor with it's polarity changed 50 times a second.

A good transformer has balanced windings and mechanical resonant points at the supply frequency minimised during it's conception stage. A mechanically sound transformer will not buzz because any movement would have been eliminated during the design and manufacturing process.

I wouldn't see why minor fluctuations in the supply AC voltage would make a transformer buzz more or less, that would just determine at which frequency it buzzes at. And I don't think most people could tell the difference between 45 and 55 Hz, which is possibly within the tolerence of power companies grid supply. If however it was designed to run at 50Hz, it might resonante at other frequencies but that could only be determined through testing.

I have two identically spec'd mains transformers, one chinese and one british. The chinese one buzzes like a detuned radio. the british one, well you can't tell when it's got current running through it or not.

Also the style of transformer matters, toroid transformers by their inherent characteristics are better balanced and less complicated so are much less likely to buzz (in fact i've never heard one buzz). Standard box-style transformers with poor separation, loose windings and poor manufacturing specs are. I'd say budget transformers have the core floating in the housing unfastened and unpotted, so a bad metal crimp or out-of-spec tooling will make it move around like a vibrator in an empty milo tin.

So to answer your question, so long as the transformer is grounded and fused, it's not dangerous even if it's buzzing like a fridge. And mains transformers aren't really repairable economically, you'd be better replacing it with a better transformer.

Chris
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Postby harry » Sun May 29, 2005 2:43 pm

Thanks for your insight guys.

it is a mechanical buzz, (it does not sound through the speaker).
there is a label on the transformer, says its made in england, hopefully i can get a direct replacement from them - although lets hope i'd get a proper transformer this time?

i guess i can live with it, but it might become a problem for recording, then again maybe not, the only way i would record with it is everything on 10, (its a 15/6w amp.)

thanks again,

if anybody knows a good amp tech in melb?
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Postby harry » Sun May 29, 2005 2:46 pm

Thanks for your insight guys.

it is a mechanical buzz, (it does not sound through the speaker).
there is a label on the transformer, says its made in england, hopefully i can get a direct replacement from them - although lets hope i'd get a proper transformer this time?

i guess i can live with it, but it might become a problem for recording, then again maybe not, the only way i would record with it is everything on 10, (its a 15/6w amp.)

thanks again,

if anybody knows a good amp tech in melb?
harry
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Postby Martinez » Sun May 29, 2005 3:21 pm

Hey Harry,

Just a coupel of points that were tuched on.

when I was looking into buying a new amp for recording,
I did some research on various sites about a number of things to do with
amps.

One was an interview with the guy I'm getting to build my new amp,
He reckons the heart and soul of a good amp is the transformer,
so if I was you I would do some research first as you never know what
you will find.
the guy building my custom amp also builds the transformers as well.


also you might want to check out the carvin web site as there is a product
they have that might be of interest to you.
its a device that cleans up the power and supplys your amp and effects
with proper voltage eliminating power fluctuations (I think thats how you spell it) its supposed to eliminate hums etc....as well.
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Postby ottowr » Wed Jun 01, 2005 1:55 pm

If the transformer has bolts holding together the plates that make up the iron core, you can try tightening them a little. The mechanical noise you are hearing is the vibration of those plates.
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Postby harry » Thu Jun 02, 2005 8:59 pm

Thanks for your ideas everybody.

I actually just thought of the bolt tightening idea the other night, i tried it and the buzz is queiter now. it does get louder however when switch the amp from standby to on. I guess that this is just inherent in the design of the amp.

The carvin device might be worth considering, thanks for your advice Martinez.
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Postby ottowr » Sat Jun 04, 2005 2:02 pm

[quote="harry"]Thanks for your ideas everybody.

it does get louder however when switch the amp from standby to on. I guess that this is just inherent in the design of the amp.

[/quote]

If the amp is manufactured in the US with a dual voltage transformer (110 or 220) then it's probaby designed to work best at 60Hz. If you replace it with a local 50Hz transformer it will be a bit happier and quieter.

otto
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