PSU problem help needed
 

Hi



I have a Watson W-30am 30-35 Amp peak power supply.



After using an IC-706 running 30-40 Watts on PSK31 for a few hours the power
supply starts making a very load buzz/hum on keying the radio. The noise
decrease's and increases turning the power up and down on the radio itself.



I have also notice the buzz/hum is still there when the radio is
disconnected and a small load say 1 Amp connected to the PSU, although the
noise is a lot quieter. So I don't think that the radio causing it.



When I start it all up the next morning the power supply is running fine
again, no noise until I have been keying the radio in PSK31 mode for several
hours when the very load concerning buzz/hum starts again.



The power supply has a top case fan that draws the heat out of the case and
the power supply case doesn't feel hot to the touch. When the load noise
occurs



Does anyone have any thoughts what could be causing this?



Thanks for any advise or help in advance.

PSU problem help needed
 

On Feb 24, 4:22*am, "Barett" wrote:
Hi

I have a Watson W-30am 30-35 Amp peak power supply.

After using an IC-706 running 30-40 Watts on PSK31 for a few hours the power
supply starts making a very load buzz/hum on keying the radio. *The noise
decrease's and increases turning the power up and down on the radio itself.

I have also notice the buzz/hum is still there when the radio is
disconnected and a small load say 1 Amp connected to the PSU, although the
noise is a lot quieter. So I don't think that the radio causing it.

When I start it all up the next morning the power supply is running fine
again, no noise until I have been keying the radio in PSK31 mode for several
hours when the very load concerning buzz/hum starts again.

The power supply has a top case fan that draws the heat out of the case and
the power supply case doesn't feel hot to the touch. When the load noise
occurs

Does anyone have any thoughts what could be causing this?

Thanks for any advise or help in advance.

I would start by tightening bolts and screws on and around the
transformer. I had a similar problem and it was a loose screw a couple
of inches away from the transformer. Keying the Tx would sometimes
cause the problem to come or go.

Jimmie

PSU problem help needed
 

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

PSU problem help needed
 

"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.

PSU problem help needed
 

On Tue, 2 Mar 2010 08:07:13 -0000, Barett wrote:

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.

Shorted windings -- probably in one of the secondary sections.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
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