What causes a transformer to buzz?

LektroiD

I just bought an amplifier from ebay, and the transformer is buzzing, I asked around a few forums if this was normal, and apparently it shouldn't buzz at all. I have a feeling the guy will not take this amplifier back, as the return policy says "The seller will not accept returns for this item.", and although the description said "Perfect working order" I doubt I'll be able to take it back as I paid cash on collection, so I can't raise a paypal dispute.

Therefore I'd like to know what my chances are of repairing this are, for as little cost as possible. When I power up, the buzz is loud then stabilizes, if I can put it to text it would look something like this... 'TZZzzzzzzzzzzzzz'

I've checked the earth continuity from the tip of the cable down to the chassis, and it is fine, If anyone knows a remedy, please let me know.

Smile

blue hell · Posted: Sat Jan 24, 2009 1:50 pm Post subject:

Transformer buzz is not that odd, and it will depend upon the construction ... likely things moved in transport casing it to buzz now where it didn't before. This is not necessarily a sign that something is broken BTW, but still it could be. In some devices the magnetic field of the transformer can interact with the steel of the case. You'd have to take a look to see what is causing the problem in your case. When the transformer is mounted with rubber dampers you might need to replace those, for instance. Or when you see something that is obviously broken you'd have to fix that. Maybe you could post some pics here.

Please remove the power before you open the amp! And when you need to reapply power while the amp is opened please take care to not touch anything that could be connected to a high voltage, when it's a tube amp high voltage could be anywhere, when its a transistor amp its likely to be only the mains connected stuff to watch out for.

cbm · Joined: Oct 25, 2005 Posts: 381 Location: San Francisco

There's a little demon in a transformer that sorts the magnetism, and if it's grumpy, it can also buzz.

blue hell · Posted: Sat Jan 24, 2009 1:56 pm Post subject:

true!

RF · Posted: Sun Jan 25, 2009 7:50 am Post subject:

Is the 'buzz' coming from the speakers - or is it actually coming from the transformer?

Loose windings in the transformer or de-lamination of the core could cause a buzz. You might be able to fix that by using some varnish on the windings.

If it's coming through the speakers it's probably bad power supply filter caps.

bruce

LektroiD · Posted: Wed Mar 04, 2009 5:00 am Post subject:

LektroiD · Posted: Fri Mar 06, 2009 9:47 am Post subject:

Ok, I managed to trickle some varnish into what I could see of the windings with a paint brush. However, no change to the buzz, I can still feel it vibrating too. Any other suggestions?

I presume from what I suggested in my previous post was not advisable, since nobody replied.

Skrog Productions · Posted: Fri Mar 06, 2009 10:53 am Post subject:

Hi, i was getting audible hum coming from my 160vA plastic encased Toroidal Xfrmr ( 2.2A per 18V winding , supplying 3 sets of rectifiers/ regulators/ smoothing caps.
Checking my current draw i was taking less than half the rating of the Xfrmr.

I had an 80vA toroidal left from the modulars previous incarnation and after reinstating i'm using almost 75% of it's rating.
Modular has 45 pcb's split between the 3 power boards.

Just out of interest i wondered what the potential was between Xfrmr 0V and mains earth ... 14.8v.

Does this affect the ground sleeve of the audio output jacks on the modular making with the ground sleeve of my yamaha mixer ??????.

As you add more modules to a big case, adequate and correct ground paths have to be considered, i'm still learning about this Laughing

hope you have luck,

Dave
from the borders