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Normal KPA500 behavior?

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Mike Walsh

Normal KPA500 behavior?

Hi,

My KPA500 does a couple of things that seem a bit odd. Other KPA owners - do your KPAs also do the following?

1) When I transmit a 500 watt carrier while displaying TEMP the displayed temperature drops 5 degrees C. When I release the key the temperature goes immediately back to the real value. Lower transmit power levels cause a correspondingly lower drop in displayed temp. This behavior causes the temp display to bounce around while transmitting CW.

2) When I power down my KPA the fan turns on (as it should) and then the right most POWER LED flashes on an off quickly. Is that LED flash normal?

Thanks and 73,

Mike - ke5akl
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N5GE

Re: Normal KPA500 behavior?

1) With CW carrier; Temperature rises as I hold down the straight key.
Temerature falls when releasing the key. While sending CW (dits and dahs)
Temperature rises. When I release the keyer paddles the temp begins to fall
within about 2 seconds.

2) Same as yours.

Temerature behavior will be different according to you fan speed settings. I
have mine set at the factory settings. The first stage comes on first and then
escalates as the temperature rises. I've never heard the fan speed escalate
above 3.

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

"Only the white eyes would believe they could cut the top
off a blanket, sew it to the bottom and have a longer
blanket."

-- American Indian comment about Daylight Saving Time --

On Fri, 10 Feb 2012 11:28:10 -0800 (PST), Mike Walsh <[hidden email]> wrote:

>Hi,
>
>My KPA500 does a couple of things that seem a bit odd. Other KPA owners - do your KPAs also do the following?
>
>1) When I transmit a 500 watt carrier while displaying TEMP the displayed temperature drops 5 degrees C. When I release the key the temperature goes immediately back to the real value. Lower transmit power levels cause a correspondingly lower drop in displayed temp. This behavior causes the temp display to bounce around while transmitting CW.
>
>2) When I power down my KPA the fan turns on (as it should) and then the right most POWER LED flashes on an off quickly. Is that LED flash normal?
>
>Thanks and 73,
>
>Mike - ke5akl

Amateur Radio Operator N5GE

Mike Walsh

Re: Normal KPA500 behavior?

Hi and thanks for the replies.

However, I think people are misunderstanding my question about the TEMP display. When I hit the key to send a 500 watt carrier the display instantly drops 5 degrees C and instantly goes back up to the real temperature when I release the key. It's that instant change in displayed temperature that I'm asking about, not the relatively slow increase or decrease associated with the real heating and cooling of the amp. Do others see that instant decrease on transmit??

73 and Thanks,

Mike - ke5akl

________________________________
From: "[hidden email]" <[hidden email]>
To: Mike Walsh <[hidden email]>
Cc: "[hidden email]" <[hidden email]>
Sent: Friday, February 10, 2012 1:18 PM
Subject: Re: [Elecraft] Normal KPA500 behavior?

1) With CW carrier; Temperature rises as I hold down the straight key.
Temerature falls when releasing the key. While sending CW (dits and dahs)
Temperature rises. When I release the keyer paddles the temp begins to fall
within about 2 seconds.

73,
Tom

-- American Indian comment about Daylight Saving Time --

On Fri, 10 Feb 2012 11:28:10 -0800 (PST), Mike Walsh <[hidden email]> wrote:

k6dgw

Re: Normal KPA500 behavior?

In reply to this post by N5GE

1. Key down [or RTTY TX], mine rises, fan steps up, temp stabilizes.
When I unkey, temp begins to fall. Sending CW, temp may fall a deg or
so when I first send, then it rises. It usually rises another deg or so
after I stop sending before falling again. I figure it's "thermal
inertia" for the PA heat to propagate to the sensor.

2. The 700 LED flashes once during the fan power-down cycle.

3. Tapping AUX QSY's the K3 to 10m. Don't know why, but I won't tap
AUX again and it won't be a problem.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2012 Cal QSO Party 6-7 Oct 2012
- www.cqp.org

> On Fri, 10 Feb 2012 11:28:10 -0800 (PST), Mike
> Walsh<[hidden email]> wrote:
>
>> Hi,
>>
>> My KPA500 does a couple of things that seem a bit odd. Other KPA
>> owners - do your KPAs also do the following?
>>
>> 1) When I transmit a 500 watt carrier while displaying TEMP the
>> displayed temperature drops 5 degrees C. When I release the key
>> the temperature goes immediately back to the real value. Lower
>> transmit power levels cause a correspondingly lower drop in
>> displayed temp. This behavior causes the temp display to bounce
>> around while transmitting CW.
>>
>> 2) When I power down my KPA the fan turns on (as it should) and
>> then the right most POWER LED flashes on an off quickly. Is that
>> LED flash normal?
>>
>> Thanks and 73,
>>
>> Mike - ke5akl
>
> ______________________________________________________________
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Oliver Dröse

Re: Normal KPA500 behavior?

In reply to this post by Mike Walsh

Mike,

that sounds like a voltage drop under load, i.e. lower voltage to the temp
measurement sensor and thus a lower reading under load. Maybe time to
contact Elecraft support? Possibly a fault in one of the low voltage
generating components. Does not seem to be normal.

73 & gl, Olli - DH8BQA
http://www.dh8bqa.de/

----- Original Message -----
From: "Mike Walsh" <[hidden email]>
To: <[hidden email]>
Cc: <[hidden email]>
Sent: Friday, February 10, 2012 9:30 PM
Subject: Re: [Elecraft] Normal KPA500 behavior?

Hi and thanks for the replies.

However, I think people are misunderstanding my question about the TEMP
display. When I hit the key to send a 500 watt carrier the display instantly
drops 5 degrees C and instantly goes back up to the real temperature when I
release the key. It's that instant change in displayed temperature that I'm
asking about, not the relatively slow increase or decrease associated with
the real heating and cooling of the amp. Do others see that instant decrease
on transmit??

73 and Thanks,

Mike - ke5akl

________________________________
From: "[hidden email]" <[hidden email]>
To: Mike Walsh <[hidden email]>
Cc: "[hidden email]" <[hidden email]>
Sent: Friday, February 10, 2012 1:18 PM
Subject: Re: [Elecraft] Normal KPA500 behavior?

1) With CW carrier; Temperature rises as I hold down the straight key.
Temerature falls when releasing the key. While sending CW (dits and dahs)
Temperature rises. When I release the keyer paddles the temp begins to fall
within about 2 seconds.

73,
Tom

-- American Indian comment about Daylight Saving Time --

On Fri, 10 Feb 2012 11:28:10 -0800 (PST), Mike Walsh <[hidden email]>
wrote:

>Hi,
>
>My KPA500 does a couple of things that seem a bit odd. Other KPA owners -
>do your KPAs also do the following?
>
>1) When I transmit a 500 watt carrier while displaying TEMP the displayed
>temperature drops 5 degrees C. When I release the key the temperature goes
>immediately back to the real value. Lower transmit power levels cause a
>correspondingly lower drop in displayed temp. This behavior causes the temp
>display to bounce around while transmitting CW.
>
>2) When I power down my KPA the fan turns on (as it should) and then the
>right most POWER LED flashes on an off quickly. Is that LED flash normal?
>
>Thanks and 73,
>
>Mike - ke5akl

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Iain MacDonnell - N6ML-2

Re: Normal KPA500 behavior?

In reply to this post by Mike Walsh

On Fri, Feb 10, 2012 at 11:28 AM, Mike Walsh <[hidden email]> wrote:
> My KPA500 does a couple of things that seem a bit odd. Other KPA owners - do your KPAs also do the following?
>
> 1) When I transmit a 500 watt carrier while displaying TEMP the displayed temperature drops 5 degrees C. When I release the key the temperature goes immediately back to the real value. Lower transmit power levels cause a correspondingly lower drop in displayed temp. This behavior causes the temp display to bounce around while transmitting CW.

This does NOT sound normal, and is something I think you should worry
about right away. If the temp sensor is not functioning correctly, you
could cause damage by not having the fans engage at the appropriate
speeds, and over-temp protection mechanisms could fail to be invoked.

Suggest contacting Elecraft support for guidance on this...

~iain / N6ML
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Bob Wolbert, K6XX

Re: Normal KPA500 behavior?

In reply to this post by Mike Walsh

Sounds like RF is getting into the temperature meter circuit. Probably
not a big deal, as 5C is only one fan speed step, but might as well
clean it up.

73 de Bob, K6XX

On 2/10/2012 12:30 PM, Mike Walsh wrote:

> Hi and thanks for the replies.
>
> However, I think people are misunderstanding my question about the TEMP display. When I hit the key to send a 500 watt carrier the display instantly drops 5 degrees C and instantly goes back up to the real temperature when I release the key. It's that instant change in displayed temperature that I'm asking about, not the relatively slow increase or decrease associated with the real heating and cooling of the amp. Do others see that instant decrease on transmit??
>
> 73 and Thanks,
>
> Mike - ke5akl
>
>
> ________________________________
> From: "[hidden email]"<[hidden email]>
> To: Mike Walsh<[hidden email]>
> Cc: "[hidden email]"<[hidden email]>
> Sent: Friday, February 10, 2012 1:18 PM
> Subject: Re: [Elecraft] Normal KPA500 behavior?
>
>
> 1) With CW carrier; Temperature rises as I hold down the straight key.
> Temerature falls when releasing the key. While sending CW (dits and dahs)
> Temperature rises. When I release the keyer paddles the temp begins to fall
> within about 2 seconds.
>
> 73,
> Tom
>
> -- American Indian comment about Daylight Saving Time --
>
>
> On Fri, 10 Feb 2012 11:28:10 -0800 (PST), Mike Walsh<[hidden email]> wrote:
>
>> Hi,
>>
>> My KPA500 does a couple of things that seem a bit odd. Other KPA owners - do your KPAs also do the following?
>>
>> 1) When I transmit a 500 watt carrier while displaying TEMP the displayed temperature drops 5 degrees C. When I release the key the temperature goes immediately back to the real value. Lower transmit power levels cause a correspondingly lower drop in displayed temp. This behavior causes the temp display to bounce around while transmitting CW.
>>
>> 2) When I power down my KPA the fan turns on (as it should) and then the right most POWER LED flashes on an off quickly. Is that LED flash normal?
>>
>> Thanks and 73,
>>
>> Mike - ke5akl
> ______________________________________________________________
> 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
>
>

N5GE

Re: Normal KPA500 behavior?

In reply to this post by Iain MacDonnell - N6ML-2

Just a note about a situation I discovered after assembling my KPA500.

It is very easy to snag the fan voltage wires at the rear of the KPA500 when
installing the rear panel if you're not careful. If it happens it will unplug
the power to the fan. It happened to me, but I noticed the heat rising right
away and corrected it.

You have to be careful that you don't snag those wires during the rear panel
installation.

I don't think that is your problem, but thought I might mention it.

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

"Only the white eyes would believe they could cut the top
off a blanket, sew it to the bottom and have a longer
blanket."

-- American Indian comment about Daylight Saving Time --

On Fri, 10 Feb 2012 12:51:26 -0800, iain macdonnell - N6ML <[hidden email]>
wrote:

>On Fri, Feb 10, 2012 at 11:28 AM, Mike Walsh <[hidden email]> wrote:
>> My KPA500 does a couple of things that seem a bit odd. Other KPA owners - do your KPAs also do the following?
>>
>> 1) When I transmit a 500 watt carrier while displaying TEMP the displayed temperature drops 5 degrees C. When I release the key the temperature goes immediately back to the real value. Lower transmit power levels cause a correspondingly lower drop in displayed temp. This behavior causes the temp display to bounce around while transmitting CW.
>
>This does NOT sound normal, and is something I think you should worry
>about right away. If the temp sensor is not functioning correctly, you
>could cause damage by not having the fans engage at the appropriate
>speeds, and over-temp protection mechanisms could fail to be invoked.
>
>Suggest contacting Elecraft support for guidance on this...
>
> ~iain / N6ML

[snip]

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Amateur Radio Operator N5GE

Mike Walsh

Re: Normal KPA500 behavior + other K3/KPA bugs

In reply to this post by Mike Walsh

Hi,

I wanted to follow up on this problem.

In response to my original post (below) a number of people responded that they were not seeing the behavior I described. After some more experimentation I found that the problem occurs primarily on 160 meters. On 160 meters, with my K3/KPA setup, the displayed KPA temp drops 5 to 6 deg C when transmitting in CW mode at 500 W. On all other bands the displayed temperature actually increases by 1 degree C -- not nearly as noticeable.

I contacted a few of the guys who responded to my original post and asked them to try the experiment of transmitting at 500 watts on 160 and watching the TEMP display. So far I've gotten two responses with both reporting seeing a similar problem. So apparently this is a design flaw in the KPA's temperature measuring.

With my KPA, when the amp gets in the temperature region where the fan kicks on, the bogus drop in temperature will turn the fan off. I don't think this would cause a serious overheating problem but it does cause the fan to cycle on and off with transmissions. Seems to me that this rapid on/off cycling can't be good for the fan.

I've also come across two other K3/KPA bugs that may be of interest.

1) If you put the K3 into "SSB + CW" mode via the CW WGHT command and set the K3 to an SSB mode, the first CW transmission after a significant change in power level will be accompanied by a short power spike. The spike only occurs on the first transmission after the power level change. The size of the spike seems to vary with the band - with my setup it's pretty bad on 10 meters and very small on 20 meters. The KPA sees the spike and, depending on the size of the spike and/or how close the drive level is to maximum output, the spike can cause the KPA to fault. In any case, with the KPA in PK HOLD mode you can see its response to the spike. This particular problem caused me a lot of trouble before I finally figured out the exact circumstance and got Elecraft to verify that it's a design problem and not a problem with my particular K3 or KPA. Apparently it's a bug in the firmware ALC routine. They say their firmware guy is tied up with the
KX3 but that he'll get to it as soon as he frees up.

2) Set the K3 up in the "per band" power mode such that the K3's STBY power is 100 W and OPER power is some reasonable drive level, say 20 watts. Set the KPA's BAND CHG menu item to STBY such that the KPA will switch to STBY when the band changes. Put the KPA into OPER mode. Change bands by hitting one of the KPA's BAND buttons. Go back to the original band. You'll find that the K3's STBY power for that band has been changed to the band OPER power - i.e. in this example, the original band's STBY power will have changed to 20 watts. Again, this appears to be a K3 firmware problem. The problem does not occur if you change bands by any other method other than the KPA's BAND buttons. Checking posts on the reflector I think I noticed some people commenting on seemingly random changes to "per band" power levels - this might be the cause.

Anyway, hope this is of interest.

73,

Mike - ke5akl

________________________________
From: Mike Walsh <[hidden email]>
To: "[hidden email]" <[hidden email]>
Sent: Friday, February 10, 2012 12:28 PM
Subject: Normal KPA500 behavior?

Hi,

My KPA500 does a couple of things that seem a bit odd. Other KPA owners - do your KPAs also do the following?

1) When I transmit a 500 watt carrier while displaying TEMP the displayed temperature drops 5 degrees C. When I release the key the temperature goes immediately back to the real value. Lower transmit power levels cause a correspondingly lower drop in displayed temp. This behavior causes the temp display to bounce around while transmitting CW.

2) When I power down my KPA the fan turns on (as it should) and then the right most POWER LED flashes on an off quickly. Is that LED flash normal?

Thanks and 73,

Mike - ke5akl
______________________________________________________________
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