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KPA500 Hum when off?

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Jim AB3CV

KPA500 Hum when off?

I leave my KPA500 back panel switch in the ON position most of the time and
use the front panel switch to bring it to life.

However in even when in the "Front panel off/Back panel on" state the
KPA500 will occasionally hum for a few seconds.

Is this normal? Any suggested causes to worry about?

Thanks

jim ab3cv
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Harlan Sherriff

Re: KPA500 Hum when off?

Jim
The KPA500 turns on the fan momentarily when you use the front panel on/off switch. I believe this is to bleed off voltage in the internal power supply. It is a design consideration not a problem

Harlan
NC3C

Sent from my Verizon Wireless 4G LTE DROID

Jim Miller <[hidden email]> wrote:

>I leave my KPA500 back panel switch in the ON position most of the time and
>use the front panel switch to bring it to life.
>
>However in even when in the "Front panel off/Back panel on" state the
>KPA500 will occasionally hum for a few seconds.
>
>Is this normal? Any suggested causes to worry about?
>
>Thanks
>
>jim ab3cv
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

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Scott Manthe-2

Re: KPA500 Hum when off?

In reply to this post by Jim AB3CV

Jim,
My first KPA500 did that occasionally, so I don't think it's an issue.
I'd guess it has to do with line voltage variances.

73,
Scott, N9AA

On 6/11/13 10:51 AM, Jim Miller wrote:

Jack Brindle-2

Re: KPA500 Hum when off?

In reply to this post by Jim AB3CV

Jim;

Make sure the transformer is bolted down appropriately. If it works loose then it will cause the hum.

Jack Brindle, W6FB

On Jun 11, 2013, at 7:51 AM, Jim Miller <[hidden email]> wrote:

> I leave my KPA500 back panel switch in the ON position most of the time and
> use the front panel switch to bring it to life.
>
> However in even when in the "Front panel off/Back panel on" state the
> KPA500 will occasionally hum for a few seconds.
>
> Is this normal? Any suggested causes to worry about?
>
> Thanks
>
> jim ab3cv
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Jim AB3CV

Re: KPA500 Hum when off?

It's not fan noise. It's definitely 60hz hum likely due to transformer for
some reason. This was a factory assembled unit. I'll take the lid off and
check it out the bolting. I'm currently running on a shared household
circuit with who-knows-what connected elsewhere. The shack will get a
dedicated 20A circuit soon.

Thanks all

Jim

On Tue, Jun 11, 2013 at 11:58 AM, Jack Brindle <[hidden email]> wrote:

> Jim;
>
> Make sure the transformer is bolted down appropriately. If it works loose
> then it will cause the hum.
>
> Jack Brindle, W6FB
>
>
> On Jun 11, 2013, at 7:51 AM, Jim Miller <[hidden email]> wrote:
>
> > I leave my KPA500 back panel switch in the ON position most of the time
> and
> > use the front panel switch to bring it to life.
> >
> > However in even when in the "Front panel off/Back panel on" state the
> > KPA500 will occasionally hum for a few seconds.
> >
> > Is this normal? Any suggested causes to worry about?
> >
> > Thanks
> >
> > jim ab3cv
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>
>
>

Stan AE7UT

Re: KPA500 Hum when off?

I have a kit-built KPA500 that has the same issue.
It's well grounded and all the bolts are tight.
The humm is barely noticeable when off but definitely there.

73
Stan AE7UT

Jack Berry

Re: KPA500 Hum when off?

My kit built hums but only periodically - more like a cycle and certainly not a continuous hum. When it happens I can fear it if the room is quiet. Capacitor recharging?

On Jun 11, 2013, at 12:13 PM, Stan AE7UT <[hidden email]> wrote:

> I have a kit-built KPA500 that has the same issue.
> It's well grounded and all the bolts are tight.
> The humm is barely noticeable when off but definitely there.
>
> 73
> Stan AE7UT
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KPA500-Hum-when-off-tp7575069p7575086.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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dmb@lightstream.net

Re: KPA500 Hum when off?

In reply to this post by Jim AB3CV

Jim,

As someone else mentioned, it is most likely due to line voltage variance.
Even though they are on different circuits, whenever my wife uses the blow
dryer, the KPA500 starts humming along. I guess that doesn't speak well
for connections somewhere between the electric company and my ac outlets,
but the issue is not with the KPA500.

73, Dale
WA8SRA

> It's not fan noise. It's definitely 60hz hum likely due to transformer for
> some reason. This was a factory assembled unit. I'll take the lid off and
> check it out the bolting. I'm currently running on a shared household
> circuit with who-knows-what connected elsewhere. The shack will get a
> dedicated 20A circuit soon.
>
> Thanks all
>
> Jim
>
>
> On Tue, Jun 11, 2013 at 11:58 AM, Jack Brindle <[hidden email]> wrote:
>
>> Jim;
>>
>> Make sure the transformer is bolted down appropriately. If it works
>> loose
>> then it will cause the hum.
>>
>> Jack Brindle, W6FB
>>
>>
>> On Jun 11, 2013, at 7:51 AM, Jim Miller <[hidden email]> wrote:
>>
>> > I leave my KPA500 back panel switch in the ON position most of the
>> time
>> and
>> > use the front panel switch to bring it to life.
>> >
>> > However in even when in the "Front panel off/Back panel on" state the
>> > KPA500 will occasionally hum for a few seconds.
>> >
>> > Is this normal? Any suggested causes to worry about?
>> >
>> > Thanks
>> >
>> > jim ab3cv
>> > ______________________________________________________________
>> > Elecraft mailing list
>> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> > Help: http://mailman.qth.net/mmfaq.htm
>> > Post: mailto:[hidden email]
>> >
>> > This list hosted by: http://www.qsl.net
>> > Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>>
> ______________________________________________________________
> Elecraft mailing list
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Eric Swartz - WA6HHQ

Re: KPA500 Hum when off?

Administrator

In reply to this post by Stan AE7UT

This is normal and is due to the small low voltage transformer and
rectifiers that provide power to the front panel microprocessor. turning
off the rear switch will turn everything off, including this transformer.

Eric
elecraft.com

On 6/11/2013 10:13 AM, Stan AE7UT wrote:

Matt Murphy

Re: KPA500 Hum when off?

I had this happen and discovered that the laser printer I had was plugged into the same ac circuit and was causing voltage drop periodically. Moving the printer to another wall outlet fixed the problem.

Matt NQ6N

On Jun 11, 2013, at 5:03 PM, "Eric Swartz - WA6HHQ, Elecraft" <[hidden email]> wrote:

> This is normal and is due to the small low voltage transformer and rectifiers that provide power to the front panel microprocessor. turning off the rear switch will turn everything off, including this transformer.
>
> Eric
> elecraft.com
>
> On 6/11/2013 10:13 AM, Stan AE7UT wrote:
>> I have a kit-built KPA500 that has the same issue.
>> It's well grounded and all the bolts are tight.
>> The humm is barely noticeable when off but definitely there.
>>
>> 73
>> Stan AE7UT
>>
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.nabble.com/KPA500-Hum-when-off-tp7575069p7575086.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
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Jim AB3CV

Re: KPA500 Hum when off?

In reply to this post by Eric Swartz - WA6HHQ

Hi Eric

It isn't a continuous hum, nor does it sound like a small transformer. It
comes on for perhaps 15 seconds, sometimes more, then goes away. Nothing
shows on the front panel when this happens as it is "off" but back panel
switch is on. It sounds more like a big transformer hum.

I've got a line voltage monitor setup now and I'll try to correlate any hum
with line fluctuations.

Thanks

jim ab3cv

On Tue, Jun 11, 2013 at 5:03 PM, Eric Swartz - WA6HHQ, Elecraft <
[hidden email]> wrote:

> This is normal and is due to the small low voltage transformer and
> rectifiers that provide power to the front panel microprocessor. turning
> off the rear switch will turn everything off, including this transformer.
>
> Eric
> elecraft.com
>
> On 6/11/2013 10:13 AM, Stan AE7UT wrote:
>
>> I have a kit-built KPA500 that has the same issue.
>> It's well grounded and all the bolts are tight.
>> The humm is barely noticeable when off but definitely there.
>>
>> 73
>> Stan AE7UT
>>
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.**
>> nabble.com/KPA500-Hum-when-**off-tp7575069p7575086.html<http://elecraft.365791.n2.nabble.com/KPA500-Hum-when-off-tp7575069p7575086.html>
>> Sent from the Elecraft mailing list archive at Nabble.com.
>>
>> ______________________________**______________________________**__
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>>
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>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
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