Low Level Hum from Mac 1900 Transformer

Is there anyway to quiet a noisy transformer in a Mac 1900 receiver? Almost sounds like the noise that ballast transformers in fluorescent lights make. It is fairly low level but very noticeable when changing records or between tracks. The hum is not in the audio chain, just emanating from the receiver. Is this just a product of its age? My backup amp is an Onkyo A-9555 but it just does not compare to the sound of the Mac.

 

I found this picture of the MAC 1900
http://i1368.photobucket.com/albums/ag199/sal350gt/Mobile Uploads/IMAG2559_zpsiu7vzudw.jpg

Make sure the loud humming/buzzing sound is coming from the power transformer. The transformer is located on the back right hand side, facing the front of the receiver.

It uses what appears to be a pretty good sized EI power transformer.
All transformers make a humming sound. Some worse than others.

I would first check the AC mains voltage at the wall receptacle with the audio system powered up. To high of an AC voltage can cause a transformer to hum louder than normal. A voltage 124Vac and higher is considered high. (Check the back of the receiver for an AC voltage rating. Is 110V, 115V, or maybe 120V?)

You also might check the 4 mounting bolts and nuts that hold the transformer to the chassis. Make sure they are tight. IF the four feet of the transformer are mounted on rubber mounts do not over tighten. Just make sure they are evenly snug.

If the power transformer was a toroidal transformer then the loud hum could be caused from DC offset on the AC mains. As a rule EI transformers are not affected by DC on the mains.

Sometimes the lamination's of an EI transformer will become loose. Not much you can do for that.

One last thing. How does the receiver sound? Plenty of power/volume?

 

Thank you for your response.

AC incoming voltage is at 119.7 and recommended voltage is 117 so that is not an issue. Transformer feels like it is snug. Most likely some delaminating due to age.

The receiver sounds absolutely fantastic with plenty of power. When music is playing, I don't hear the noise so I can just live with it.

 

You could try an AVA Humdinger. They are quite effective, and if it doesn't work in your application, you can send it back. I have 3 of them and wouldn't be without them.