A/C Transformer Hum

A Trane dealer installed a new a/c unit last fall. It has been working fine but I just wanted to get an independent opinion about something.
There is a constant low-level hum coming from the inside unit even when the fan is not blowing, just enough to be noticeable near the unit when the house is quiet.
I called the installer and they sent someone out who identified it as transformer hum and he ordered a new transformer. After the new part was installed, the humming noise is still there. My previous 20-year old unit was quiet in-between cycles. I Is this considered normal? Do you think it's the transformer itself or does some housing just need to be tightened?
Thanks.
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pixel_a snipped-for-privacy@yahoo.com wrote:

Hi, If it is loosely mounted or iron core lamination is loose it can hum (really slight mechanical vibration at 60Hz). Or it could be cheaply built one with bad core material. If tightening everything does not fix it, try another brand. If it is not hot to touch the hum itself won't hurt anything. Just my two bits.
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Transformer... it's normal for today's equipment.
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I don't know what your fussing about, I love a good hummer ;-)
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On Mon, 08 Oct 2007 08:17:18 -0700, pixel_a snipped-for-privacy@yahoo.com wrote:

Sometimes, if you take the door off the unit and bash the transformer with a rock a bit, it will stop the hum. If there is anything left of the rock when you finish, please take it to Stormy and let him finish some self administered bashing. Bubba
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As T. Hwang put it I agree, if you are annoyed with hum try another MFG. there is no reason for small trns. to hum unless is made in Korea or china or maybe Mexico but again that is my opinion, don't blame service person because he must use what is suggested by OEM Tony

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That eliminates 99% of them. LOL
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