[AMRadio] transformer rattle - kill or cure?

Stevan A. White w5saw at pathwayz.com
Wed Dec 23 12:06:19 EST 2009

As a broadcast engineer I have seen (or heard) transformers rattle as 
you've described.  My suggestion would be to let it be, especially if it 
stops after a while.  It sounds to me like it rattles when it's cold and 
stops after it warms up.  Does the noise gradually subside or just quit 
abruptly?  It is annoying to listen to the laminations rattle but it 
would be even more annoying to try to "fix" one problem and create 
another.  Some transformer windings are spaced apart and spacers may 
loosen some when they're cool and "tighten up" after they warm up.  I 
used to have one that did that and it really bothered me until I talked 
to the factory guy and he explained what was happening.  Even worse than 
transformer laminations rattling is hearing a bank of SCRs grunting and 
groaning.  (I'll bet some on this list even know which line of 
transmitters I'm talking about.)  Happy Holidays to all!

Steve White, W5SAW

Todd, KA1KAQ wrote:
> On Wed, Dec 23, 2009 at 10:39 AM, AirRadio <AirRadio at dsl.pipex.com> wrote:
>> I have a mains transformer in my latest boatanchor, it is rattling like mad, eventually goes away after an hour or so, I thought about dropping it in a can of varnish, anyone cured one before, any luck or waste of time?
> Sounds like it abates once things settle in thermally.The simple
> approach I'd try first Max is to check the tension on any securing
> bolts through the transformer laminations or chassis. Sometimes that
> takes care of it. Other methods include removing the transformer and
> re-sealing the laminations it in hot varnish, or isolating the
> transformer from the chassis on rubber bushings. The latter is not a
> good idea IMO due to safety concerns with internal shorts which would
> otherwise become apparent when the case is grounded to the chassis.
> Gary WZ1M is a member of this list and has a transformer rebuilding
> business, so he can certainly provide you with some pointers. I think
> Don K4KYV and a few others have successfully dealt with similar
> problems with success. It might be as simple as tossing he transformer
> in the oven for a while on its own if tightening the bolts doesn't
> cure it.
> ~ Todd,  KA1KAQ/4
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