Mains power transformer on S5 K-12 kit hums? - diyAudio
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Old 18th August 2010, 07:06 AM   #1
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Default Mains power transformer on S5 K-12 kit hums?

Hello all, I've been greatly enjoying my S5 amp setup, with one exception: just recently the mains power transofmer has started to hum. When some pressure is applied to the yellow taped portion where the 2 main power leads enter the transformer, the hum goes away, but then it eventually comes back. Is there any thing I can do to prevent / stop the hum? Will I need to replace the mains power transformer? Because its a sin when the amp sounds crystal clear with no extraneous noise or hum and then the power adapter starts humming at a low volume.

Last edited by Maxwell Smart; 18th August 2010 at 07:13 AM.
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Old 18th August 2010, 12:33 PM   #2
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Location: Alps:Tube amp designs over 150W, SMPS guru.
Make sure the tranny frame is well screwed down beit shrouds or chassis to avoid the outer laminations buzzing. If the noise is coming from a loose E in the internal core, the only remedy is to dismantle unit from chassis, take covers off and drop the whole tranny it in a tin of polyuothane varnish and leave overnight.
Failing that a new tranny and hope.

It is a common dilemma; many tranny manufacturers use that yellow helf healing tape for the windings and when tranny finished assembled, simply do 2 dips in the varnish tank then leave to air dry without windings being properly impregnated. Vacuum impregnation is the compliance method which completely soaks every winding and core. A core made under this method is hell to split the laminations.

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Old 18th August 2010, 06:09 PM   #3
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Interesting. Well it sounds just like a faulty power transformer, so I will contact S5 electronics in the hopes of getting a replacement. Thanks for your help.
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