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Recreational Discussion: PSU Problem Help NeededGroup: rec.radio.amateur.homebrew
Discussion: PSU Problem Help Needed
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Fred McKenzie
Mar 01, 2010 - 02:27:47 pm EST
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



Barett
Mar 02, 2010 - 03:07:13 am EST
"Fred McKenzie" wrote in message
news:fmmck-E25ED0.14274701032010 [No Spam] 5ad64b5e.bb.sky.com...
> 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.






Highlandham
Mar 02, 2010 - 07:43:46 am EST
Barett wrote:
> "Fred McKenzie" wrote in message
> news:fmmck-E25ED0.14274701032010 [No Spam] 5ad64b5e.bb.sky.com...
>> 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.
============================
With the secondary of the transformer not connected to anything and the
transformer primary winding drawing 300 mA and at 230V that means abt 70
Watts ,it follows that the transformer must be defective ;
possible an internal shortage due to failing insulation .
Indeed 70 Watts will heat up the transformer after a while up to a
'don't touch' level.

Frank GM0CSZ / KN6WH



Allodoxaphobia
Mar 02, 2010 - 09:57:27 am EST
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
38.24N 104.55W | [No Spam] config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm



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