HELP ON SB401 HUM

[Dan Pividal N4VET]

I have an SB401 SB301 combo.
When I key the mike I can hear a hum when I put my ear up to the cabinet over
the transformer.
I was told by a fellow HAM that he could hear a hum when I keyed my mike.
Another station I talk to all the time told me he also noticed a hum.
Both of these stations are about 2 miles from my house and both told me that
since I was hitting them at 20 over and a station further away would probably
not hear the hum.
I do not see the hum on my scope when I key but I do hear a hum on keydown on
my Kenwood with its antenna disconnected.
My meter tells me that the HV is 800 when I transmit it drops to about 750
CW. This seems to be right.
Has anyone had this problem?
Any help from anyone as to how to resolve?
Is this common problem and if so any mods?
Thanks,
Dan N4VET

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://interactive.tempe.gov/archives/HEATH.html