[R-390] R-390A power transformer hum

[Ing. Giovanni Becattini]

Mine is rather noisy.  At 40 cms it increases the room noise by 4-5 dBs.

> Il giorno 19 ott 2024, alle ore 15:18, Leo Reynolds via R-390 <r-390 at mailman.qth.net> ha scritto:
> 
> Is it normal for a R-390A power transformer to hum audibly? Not through the speaker, though there is a little there too, but through slight chassis vibration. It is there from the instant of turning on power and changes slightly as the rectifier starts conducting and B+ flows. It is easily audible in the shack, as if it were a small AM broadcast transmitter minus the blower.
> 
> Thanks,
> 
> Leo Reynolds 
> K4LDR
> 
> 
> 
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