In article ,
"Barett" wrote:

The fuse has now blown. I replaced the fuse and it blew again. Disconnected
all secondary outputs and put a new fuse in and the transformer is working.

Barett-

Your original question was about a buzz. I think you now have a second
problem now.

The buzz may be caused by "magnetostriction" in the laminated
transformer core. This effect is the lengthening and shortening of the
metal laminations in response to the 60 Hz magnetic field. The
laminations slide across each other at a 60 Hz rate, resulting in a
buzz. There may be a varnish coating on the laminations, that becomes
viscous after getting hot. As others mentioned, the bolts holding the
transformer together may have loosened, allowing the buzz to get worse
over time. The buzz may bother you, but is probably not a problem
otherwise.

When you say outputs are disconnected, do you mean you disconnected the
transformer secondary wires, or that you just disconnected the IC-706?
If just the IC-706, the radio may have a problem rather than the power
supply. I understand the IC-706 final output transistor collectors are
connected directly across the power supply and are not switched. If one
happens to short, it would blow the fuse.

Fred
K4DII