Re: {Collins} R-390a hum *within* the audio module?

This would probably be due to loose laminates in the power transformer itself and that happens pretty often in various gear where potting compounds can dry out. I am not really familiar with the R-390 module and the transformer is probably a completely potted one in a sealed can. This can be hard to fix and you may have to live with it. It will not hurt anything that I know of. If it is not a sealed transformer, taking it to a motor or transformer shop and having it evacuated and repotted will solve the problem - if tightening frame screws does not.

Hope this helps and good luck........

Bill Carns, N7OTQ
K0CXX, Trustee MRCCC
Editor Signal Magazine
CCA Acting President & Board Member
CCA # 94-00009, Founding Board Member
Wimberley, Texas
512 847 7010
512 618 2762 (Cell)

----- Original Message ----- From: "bob bauer" <bbauer@xxxxxxxxxxxxxxxx>
To: "Collins" <collins@xxxxxxxxxxxxx>
Sent: Thursday, February 11, 2010 12:05 PM
Subject: {Collins} R-390a hum *within* the audio module?

My apologies if this is only a question because of my inability to do a
google search with the right keywords, but everything I've found so far
regarding an R-390a with hum from the audio module refers to a hum that's
actually heard in headphones or speakers -- I'm trying to identify why the
module itself would hum loudly--if it's something to be concerned about and
if so, any suggestions on where to start.

As far as I've been able to determine, none of the outer components are
vibrating and causing the humming sound...if you've ever used a cheap
charger on your car's battery, it's about the same loudness.



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