[drakelist] transformer hum in L-4B rf unit

[AirRadio]

I have just rebuilt my L-4B power unit and fitted the new cap/diode board from 
the HK man. it works very well indeed and is a worthwhile and easy mod, anyway 
to the point, the RF deck transformer hums quite loudly I cannot remember it 
doing it before but it is a while since I ran this one, not a major problem but 
is there a cure? I notice by re adjusting the outer case it does make a small 
difference, any ideas? 73 Max