"Fred McKenzie" wrote in message
...
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

With he 706 disconnected from the supply I put a new fuse and it blew. I
then disconnected all the secondary wires from the transformer and put a new
fuse in and it didn't blow.

I put the multi meter in series with the mains wire input to the transformer
and I got a reading of 300mA with all wires disconnected from the secondary
side of the transformer. I left the transformer switched on for a few hours
the transformer got too hot to touch and I could smell the heat from it.
This is the stage I'm up to at the moment Fred.