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KPA-500 HUM from PA and not from Speaker !!!

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Klaus Koppendorfer

KPA-500 HUM from PA and not from Speaker !!!

discussion is drifting away to amplified speakers but there is realy a problem with
HUM comming from KPA500

1) HUM during transmit
2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on

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Ken Chandler

Re: KPA-500 HUM

Hi
I took part in IOTA contest at the weekend in the unassisted category, CW, high power.
The KPA-500 was used for the first full 24hrs contest here with M3i call-sign and I did give it a darn good work-out end result performance was just fab.
No hang-ups, instant power, band change, big pile-ups lots of QSO's LOTS of fun.
It just loofed along, the fan came on occasionally but was not loud, my PC's fan is louder than the amp.
HOWEVER
after the contest, pc switched off, k3 on, amp still on in standby mode,
Their is a HUM from the amp and was fairly noticeable.
Turning off the rear switch cured it!!!
Perhaps one for the engineers to look at, as I'm sure they will, and are already on the case!!!!

Ken..G0ORH / M3i KPA-500 sn 212

Sent from my iPhone

On 3 Aug 2011, at 07:08, Klaus Koppendorfer <[hidden email]> wrote:

> discussion is drifting away to amplified speakers but there is realy a problem with
> HUM comming from KPA500
>
> 1) HUM during transmit
> 2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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Eric Swartz - WA6HHQ

Re: KPA-500 HUM

Administrator

When the back panel switch is on, the low voltage power supply for the
front panel is still on, allowing the microprocessor to read the front
panel 'power' switch and talk over RS-232. A low level of power supply
hum from this small transformer is totally normal in this case. Of
course, turnig off the rear switch on the KPA500 shuts down everyhting.
Its perfectly OK to use the rear switch as the main on/off power control.

The KPA500 front panel power switch is a 'soft' switch that controls the
HV supply relay etc. This allows remote control over RS-232 to power
up/down the amp etc.

73, Eric WA6HHQ

---
www.elecraft.com

On 8/3/2011 1:09 AM, Ken Chandler wrote:

> Hi
> I took part in IOTA contest at the weekend in the unassisted category, CW, high power.
> The KPA-500 was used for the first full 24hrs contest here with M3i call-sign and I did give it a darn good work-out end result performance was just fab.
> No hang-ups, instant power, band change, big pile-ups lots of QSO's LOTS of fun.
> It just loofed along, the fan came on occasionally but was not loud, my PC's fan is louder than the amp.
> HOWEVER
> after the contest, pc switched off, k3 on, amp still on in standby mode,
> Their is a HUM from the amp and was fairly noticeable.
> Turning off the rear switch cured it!!!
> Perhaps one for the engineers to look at, as I'm sure they will, and are already on the case!!!!
>
> Ken..G0ORH / M3i KPA-500 sn 212
>
> Sent from my iPhone
>
>
>
>
>
> On 3 Aug 2011, at 07:08, Klaus Koppendorfer<[hidden email]> wrote:
>
>> discussion is drifting away to amplified speakers but there is realy a problem with
>> HUM comming from KPA500
>>
>> 1) HUM during transmit
>> 2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>
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>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
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Rick Tavan N6XI

Re: KPA-500 HUM from PA and not from Speaker !!!

In reply to this post by Klaus Koppendorfer

I have experienced absolutely no hum, either mechanical or electrical,
associated with my KPA500 in either of my two ham shacks.

/Rick N6XI

On Tue, Aug 2, 2011 at 11:08 PM, Klaus Koppendorfer <[hidden email]> wrote:

> discussion is drifting away to amplified speakers but there is realy a
> problem with
> HUM comming from KPA500
>
> 1) HUM during transmit
> 2) HUM somes sometimes when the KPA500 is off, but on line and backswitch
> on
>
>
--
Rick Tavan N6XI
Truckee, CA
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N5GE

Re: KPA-500 HUM from PA and not from Speaker !!!

In reply to this post by Klaus Koppendorfer

Klaus,

I know you've already contacted Elecraft Support about this. Right?

If you have not, you will have a good deal more success contacting them, since
they have probably already seen this before and know what to look for.

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

On Wed, 3 Aug 2011 06:08:42 +0000, Klaus Koppendorfer <[hidden email]> wrote:

>discussion is drifting away to amplified speakers but there is realy a problem with
>HUM comming from KPA500
>
>1) HUM during transmit
>2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on
>
[snip]

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Amateur Radio Operator N5GE

Eric Swartz - WA6HHQ

Re: KPA-500 HUM

Administrator

In reply to this post by Eric Swartz - WA6HHQ

One clarification to my last post.

It is important that users power off the KPA500 using the front panel
power switch before killing power with the rear panel switch.

If you only use the rear panel power switch for main power then any
changed parameters (including last band) will not be saved at power off.

73, Eric WA6HHQ

---
www.elecraft.com

On 8/3/2011 8:55 AM, Eric Swartz - WA6HHQ, Elecraft wrote:

> When the back panel switch is on, the low voltage power supply for the
> front panel is still on, allowing the microprocessor to read the front
> panel 'power' switch and talk over RS-232. A low level of power supply
> hum from this small transformer is totally normal in this case. Of
> course, turnig off the rear switch on the KPA500 shuts down everyhting.
> Its perfectly OK to use the rear switch as the main on/off power control.
>
> The KPA500 front panel power switch is a 'soft' switch that controls the
> HV supply relay etc. This allows remote control over RS-232 to power
> up/down the amp etc.
>
> 73, Eric WA6HHQ

Eric Swartz - WA6HHQ

Re: KPA-500 HUM from PA and not from Speaker !!!

Administrator

In reply to this post by N5GE

Bob, our KPA500 engineering project manager, will be contacting Klaus.

73, Eric WA6HHQ

---
www.elecraft.com

On 8/3/2011 1:37 PM, [hidden email] wrote:

> Klaus,
>
> I know you've already contacted Elecraft Support about this. Right?
>
> If you have not, you will have a good deal more success contacting them, since
> they have probably already seen this before and know what to look for.
>
> 73,
> Tom
> Amateur Radio Operator N5GE
> ARRL Lifetime Member
> QCWA Lifetime Member
>
>
> On Wed, 3 Aug 2011 06:08:42 +0000, Klaus Koppendorfer<[hidden email]> wrote:
>
>> discussion is drifting away to amplified speakers but there is realy a problem with
>> HUM comming from KPA500
>>
>> 1) HUM during transmit
>> 2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on
>>

k6dgw

Re: KPA-500 HUM from PA and not from Speaker !!!

In reply to this post by Rick Tavan N6XI

On 8/3/2011 9:40 AM, Rick Tavan N6XI wrote:
> I have experienced absolutely no hum, either mechanical or electrical,
> associated with my KPA500 in either of my two ham shacks.
>
> /Rick N6XI

Nor have I in my one ham shack. In fact, the only time I've heard the
fans come on is when I shut the amp off at the front panel *and* have my
hearing aids back in. YMMV, but my K3 and KPA500 appear to be silent
devices.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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Richard Griest

Re: KPA-500 HUM from PA and not from Speaker !!!

Ken Chandler

Re: KPA-500 HUM

In reply to this post by Eric Swartz - WA6HHQ

Hi Eric
Thanks for the email.
It's not a problem..... really. In fact
I'm now seriously thinking of buying a 2nd kpa500 amp for SO2R!

Cheers

Ken..G0ORH

Sent from my iPhone

On 3 Aug 2011, at 16:55, "Eric Swartz - WA6HHQ, Elecraft" <[hidden email]> wrote:

> When the back panel switch is on, the low voltage power supply for the front panel is still on, allowing the microprocessor to read the front panel 'power' switch and talk over RS-232. A low level of power supply hum from this small transformer is totally normal in this case. Of course, turnig off the rear switch on the KPA500 shuts down everyhting. Its perfectly OK to use the rear switch as the main on/off power control.
>
> The KPA500 front panel power switch is a 'soft' switch that controls the HV supply relay etc. This allows remote control over RS-232 to power up/down the amp etc.
>
> 73, Eric WA6HHQ
>
> ---
> www.elecraft.com
>
>
> On 8/3/2011 1:09 AM, Ken Chandler wrote:
>> Hi
>> I took part in IOTA contest at the weekend in the unassisted category, CW, high power.
>> The KPA-500 was used for the first full 24hrs contest here with M3i call-sign and I did give it a darn good work-out end result performance was just fab.
>> No hang-ups, instant power, band change, big pile-ups lots of QSO's LOTS of fun.
>> It just loofed along, the fan came on occasionally but was not loud, my PC's fan is louder than the amp.
>> HOWEVER
>> after the contest, pc switched off, k3 on, amp still on in standby mode,
>> Their is a HUM from the amp and was fairly noticeable.
>> Turning off the rear switch cured it!!!
>> Perhaps one for the engineers to look at, as I'm sure they will, and are already on the case!!!!
>>
>> Ken..G0ORH / M3i KPA-500 sn 212
>>
>> Sent from my iPhone
>>
>>
>>
>>
>>
>> On 3 Aug 2011, at 07:08, Klaus Koppendorfer<[hidden email]> wrote:
>>
>>> discussion is drifting away to amplified speakers but there is realy a problem with
>>> HUM comming from KPA500
>>>
>>> 1) HUM during transmit
>>> 2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on
>>>
>>>
>>> ______________________________________________________________
>>> 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
>> 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

David Pratt

Re: KPA-500 HUM

In a recent message, Ken Chandler <[hidden email]> writes
>
>I'm now seriously thinking of buying a 2nd kpa500 amp for SO2R!
>
>Cheers
>
>Ken..G0ORH
>
>Sent from my iPhone

Alternatively, Ken, you could operate your second KPA500 in parallel to
run the full 1kW ;-)

73 de David G4DMP

Sent from my Netbook

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g3ymc

Re: KPA-500 HUM

SO2R means single operator two receivers. Where does a second linear
come into this?

73 Dave G3YMC

On 4 Aug 2011 at 7:46, David Pratt wrote:

> >
> >I'm now seriously thinking of buying a 2nd kpa500 amp for SO2R!
> >
> >Cheers
> >
> >Ken..G0ORH
>
> Alternatively, Ken, you could operate your second KPA500 in parallel to
> run the full 1kW ;-)
>

http://www.davesergeant.com

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Gary Gregory

Re: KPA-500 HUM

Dang....me thunked it meant Single Operator Two Radios...my bad!

:-)

Gary

On 4 August 2011 17:15, Dave Sergeant <[hidden email]> wrote:

> SO2R means single operator two receivers. Where does a second linear
> come into this?
>
> 73 Dave G3YMC
>
> On 4 Aug 2011 at 7:46, David Pratt wrote:
>
> > >
> > >I'm now seriously thinking of buying a 2nd kpa500 amp for SO2R!
> > >
> > >Cheers
> > >
> > >Ken..G0ORH
> >
> > Alternatively, Ken, you could operate your second KPA500 in parallel to
> > run the full 1kW ;-)
> >
>
>
> http://www.davesergeant.com
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

--

VK4FD - Motorhome Mobile
Elecraft Equipment
K3 #679, KPA-500 #018
Living the dream!!!
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David Pratt

Re: KPA-500 HUM

Correct - a 'Radio' is really a receiver. Perhaps he meant SO2T -
'Single Operator, Two Transceivers'

The use of the word 'Radio' to mean 'Transceiver' migrated from the
world of CB :-( In amateur radio we always used to refer to our
equipment as a rig or a transceiver. But the CB world has a lot to
answer for.

73 de David G4DMP

In a recent message, Gary Gregory <[hidden email]> writes

>
>Dang....me thunked it meant Single Operator Two Radios...my bad!
>
>:-)
>
>Gary
>
>On 4 August 2011 17:15, Dave Sergeant <[hidden email]> wrote:
>
>> SO2R means single operator two receivers. Where does a second linear
>> come into this?
>>
>> 73 Dave G3YMC
>>
>> On 4 Aug 2011 at 7:46, David Pratt wrote:
>>
>> > >
>> > >I'm now seriously thinking of buying a 2nd kpa500 amp for SO2R!
>> > >
>> > >Cheers
>> > >
>> > >Ken..G0ORH
>> >
>> > Alternatively, Ken, you could operate your second KPA500 in parallel to
>> > run the full 1kW ;-)
>> >
>>
>>
>> http://www.davesergeant.com
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>
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>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
>

--
+ - - - - - - - - - - - - - - - - +
| David M Pratt, Kippax, Leeds. |
| Website: http://www.g4dmp.co.uk |
+ - - - - - - - - - - - - - - - - +

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Ken Chandler

Re: KPA-500 HUM

Excuse me......!!!!!!!!

Ken..G0ORH

Sent from my iPhone

On 4 Aug 2011, at 09:46, David Pratt <[hidden email]> wrote:

> Correct - a 'Radio' is really a receiver. Perhaps he meant SO2T -
> 'Single Operator, Two Transceivers'
>
> The use of the word 'Radio' to mean 'Transceiver' migrated from the
> world of CB :-( In amateur radio we always used to refer to our
> equipment as a rig or a transceiver. But the CB world has a lot to
> answer for.
>
> 73 de David G4DMP
>
> In a recent message, Gary Gregory <[hidden email]> writes
>>
>> Dang....me thunked it meant Single Operator Two Radios...my bad!
>>
>> :-)
>>
>> Gary
>>
>> On 4 August 2011 17:15, Dave Sergeant <[hidden email]> wrote:
>>
>>> SO2R means single operator two receivers. Where does a second linear
>>> come into this?
>>>
>>> 73 Dave G3YMC
>>>
>>> On 4 Aug 2011 at 7:46, David Pratt wrote:
>>>
>>>>>
>>>>> I'm now seriously thinking of buying a 2nd kpa500 amp for SO2R!
>>>>>
>>>>> Cheers
>>>>>
>>>>> Ken..G0ORH
>>>>
>>>> Alternatively, Ken, you could operate your second KPA500 in parallel to
>>>> run the full 1kW ;-)
>>>>
>>>
>>>
>>> http://www.davesergeant.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
>>>
>>
>>
>>
>
> --
> + - - - - - - - - - - - - - - - - +
> | David M Pratt, Kippax, Leeds. |
> | Website: http://www.g4dmp.co.uk |
> + - - - - - - - - - - - - - - - - +
>
>
>
> ______________________________________________________________
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ke9uw

Re: KPA-500 HUM from PA and not from Speaker !!!

In reply to this post by k6dgw

The hum seems to be the 50 Hertz power supplies?

Chuck, KE9UW

Dan AE9K

Re: KPA-500 with and without transformer buzz

I've experienced silent operation and operation with hum (what I'd call more of a transformer buzz).

My mains are between 248V and 249V so I used the yellow tap per the table in the manual (the 231V to 250V tap). The HV then idles around 72.4V and on full power transmit, HV went down around 57V. In this configuration, full power transmit is silent, no buzz.

But per the errata for the manual for best linearity HV should be 60V or higher during full power transmit. So, I switched to the red tap (the 211 to 230V tap). HV now idles at 80.0V and goes no lower than 64V on full power transmit. Linearity achieved, but in this configuration I get a noticeable transformer buzz. I opened the top and made sure everything was secure - no change.

So, by changing the transformer voltage selection tap I've had both silent and with-buzz operation.

At first I was concerned the buzz was an indication I was tapped too low for the high mains voltage but the 80V to 64V range is well within spec so I assumed I was ok to leave it that way. Still seems odd that I have to tap down when I'm so close to the max input voltage.

Dan
AE9K