KPA500 finals blown

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KPA500 finals blown

Nand Kishore
KPA500 shut off with a bang while operating RTTY @300W.

Antenna is a steppir beam.

On opening the KPA500,found 2 ceramic? caps of VRF2933
adrift with underside of the said caps,black.

Have written to support.Is this the first time this has happened
in a KPA500?

73 and HNY,
Nandu
VU2NKS
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Re: KPA500 finals blown

efortner
I would like to know what the continous keydown power output rating is. The
manual talks about ICAS. I know when I get on RTTY I does not take long for
The fans to come up to full speed running 300 watts.

Earl, K4Kay

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Nand
Kishore
Sent: Thursday, January 21, 2016 4:29 AM
To: elecraft
Subject: [Elecraft] KPA500 finals blown

KPA500 shut off with a bang while operating RTTY @300W.

Antenna is a steppir beam.

On opening the KPA500,found 2 ceramic? caps of VRF2933
adrift with underside of the said caps,black.

Have written to support.Is this the first time this has happened
in a KPA500?

73 and HNY,
Nandu
VU2NKS
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CESSB Duty Cycle

Bob McGraw - K4TAX
The recent article in February QST describing the CESSB mode is of
interest.  Just wondering if that mode can or will be added to the code
operating the K3S?   Also, wondering if the higher duty cycle of the
CESSB mode will exceed the ratings of the PA stage and that of the
KPA500?  From what I read it seems that most SSB rated amps, past and
present,  may have inadequate ratings for the higher duty cycle.

Thoughts?

73
Bob, K4TAX

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Re: KPA500 finals blown

Bob McGraw - K4TAX
In reply to this post by efortner
As applied to solid-state transmitters, ICAS does not imply reduced
device life, as unlike vacuum tubes, the RF power devices are not
regarded as consumables. Rather, ICAS in a solid-state environment
implies de-rating to keep the device junction and case temperatures
within their maximum ratings. Thus, ICAS suggests a limited operating or
'on' period followed by an 'off' or standby period of at least the same
or longer duration, whilst CCS assumes continuous, key-down operation at
reduced output (assuming the same heatsink area and/or fan air-flow
rating for both applications).

Typically, a PA cooling system should be designed to keep the device
case temperature in the range 70 ~ 80ºC (158 ~ 176ºF) at 25ºC (77ºF)
ambient, for a 30-minute SSB voice transmission or a 5- to 10-minute
“key-down” CW transmission at rated output. These are minimal duty cycle
values for an amplifier operating in average amateur service. Longer
“key-down” intervals, necessitating larger heat-dissipating surfaces and
greater air circulation, are required for contest operation or at high
ambient temperatures.


73
Bob, K4TAX



On 1/21/2016 8:44 AM, efortner wrote:

> I would like to know what the continous keydown power output rating is. The
> manual talks about ICAS. I know when I get on RTTY I does not take long for
> The fans to come up to full speed running 300 watts.
>
> Earl, K4Kay
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of Nand
> Kishore
> Sent: Thursday, January 21, 2016 4:29 AM
> To: elecraft
> Subject: [Elecraft] KPA500 finals blown
>
> KPA500 shut off with a bang while operating RTTY @300W.
>
> Antenna is a steppir beam.
>
> On opening the KPA500,found 2 ceramic? caps of VRF2933
> adrift with underside of the said caps,black.
>
> Have written to support.Is this the first time this has happened
> in a KPA500?
>
> 73 and HNY,
> Nandu
> VU2NKS
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>
> ______________________________________________________________
> 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
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Re: CESSB Duty Cycle

wayne burdick
Administrator
In reply to this post by Bob McGraw - K4TAX
The finals could handle it, just as they handle full-carrier modes like RTTY and FM. The bigger problem, specifically described in the article, is the power supply. Many operators who use SSB or CW only, not full-carrier modes, are using power supplies that are barely adequate. They can handle 20+ amps at light duty cycle, but not CESSB, etc.

As I mentioned previously, both the K3/K3S and KX3 have excellent speech compression already, and the difference between a fairly aggressive compression setting and CESSB is, in practice, rarely going to make a difference. That said, we will be playing with this in DSP code to see if it's worth the trouble.

Wayne
N6KR



On Jan 21, 2016, at 6:56 AM, Bob McGraw K4TAX <[hidden email]> wrote:

> The recent article in February QST describing the CESSB mode is of interest.  Just wondering if that mode can or will be added to the code operating the K3S?   Also, wondering if the higher duty cycle of the CESSB mode will exceed the ratings of the PA stage and that of the KPA500?  From what I read it seems that most SSB rated amps, past and present,  may have inadequate ratings for the higher duty cycle.
>
> Thoughts?
>
> 73
> Bob, K4TAX



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Re: CESSB Duty Cycle

GM4JJJ
In reply to this post by Bob McGraw - K4TAX
Hi Bob,

It was an interesting article as are the QEX articles by the same author.

That QST article concludes that the RF amplifier likely won't be +thermally+ strained by the CESSB, as if means that amplifier stages are operating further towards the higher efficiency point. Normal SSB has lower average power but may as a result have increased dissipation because class AB RF amplifier efficiency drops at lower power.

However the author points out that +power supplies+ may well be strained by CESSB as average current will increase. Where you have an external PSU for your K3S it might not be a problem, but it may be with the KPA500 I suppose.

I can't speak for Elecraft and the K3(S), but in a recent email on the subject of possibly adding CESSB to the KX3, Wayne said they will look into it. No discussion was started about the K3 or K3S on this though, but you have asked, so perhaps we might get a hint on that too.

73 from David GM4JJJ

> On 21 Jan 2016, at 14:56, Bob McGraw K4TAX <[hidden email]> wrote:
>
> The recent article in February QST describing the CESSB mode is of interest.  Just wondering if that mode can or will be added to the code operating the K3S?   Also, wondering if the higher duty cycle of the CESSB mode will exceed the ratings of the PA stage and that of the KPA500?  From what I read it seems that most SSB rated amps, past and present,  may have inadequate ratings for the higher duty cycle.
>
> Thoughts?
>
> 73
> Bob, K4TAX
>
> ______________________________________________________________
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Re: KPA500 finals blown

Phil Wheeler-2
In reply to this post by efortner
This in the specs in the KPA500 manual "Duty Cycle
at 500 Watts 10 minutes key down / 5 minutes
standby" seems pretty definitive for normal
operations, even RTTY, Earl.

73, Phil W7OX

On 1/21/16 6:44 AM, efortner wrote:

> I would like to know what the continous keydown power output rating is. The
> manual talks about ICAS. I know when I get on RTTY I does not take long for
> The fans to come up to full speed running 300 watts.
>
> Earl, K4Kay
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of Nand
> Kishore
> Sent: Thursday, January 21, 2016 4:29 AM
> To: elecraft
> Subject: [Elecraft] KPA500 finals blown
>
> KPA500 shut off with a bang while operating RTTY @300W.
>
> Antenna is a steppir beam.
>
> On opening the KPA500,found 2 ceramic? caps of VRF2933
> adrift with underside of the said caps,black.
>
> Have written to support.Is this the first time this has happened
> in a KPA500?
>
> 73 and HNY,
> Nandu
> VU2NKS

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Re: KPA500 finals blown

Irwin Darack
In discussions with Elecraft at Dayton, we should be able to run the KPA500
at 300 watts during a RTTY contest. This would include Running versus S/P.
The fans on mine do come on high and I keep an eye on the temp reading. I
do need to stop occasionally to allow the amp to cool down. I am not sure
if there is a way to add an addition external fan to increase the air flow?

Irwin KD3TB

On Thursday, January 21, 2016, Phil Wheeler <[hidden email]> wrote:

> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 minutes
> key down / 5 minutes standby" seems pretty definitive for normal
> operations, even RTTY, Earl.
>
> 73, Phil W7OX
>
> On 1/21/16 6:44 AM, efortner wrote:
>
>> I would like to know what the continous keydown power output rating is.
>> The
>> manual talks about ICAS. I know when I get on RTTY I does not take long
>> for
>> The fans to come up to full speed running 300 watts.
>>
>> Earl, K4Kay
>>
>> -----Original Message-----
>> From: Elecraft [mailto:[hidden email]] On Behalf Of
>> Nand
>> Kishore
>> Sent: Thursday, January 21, 2016 4:29 AM
>> To: elecraft
>> Subject: [Elecraft] KPA500 finals blown
>>
>> KPA500 shut off with a bang while operating RTTY @300W.
>>
>> Antenna is a steppir beam.
>>
>> On opening the KPA500,found 2 ceramic? caps of VRF2933
>> adrift with underside of the said caps,black.
>>
>> Have written to support.Is this the first time this has happened
>> in a KPA500?
>>
>> 73 and HNY,
>> Nandu
>> VU2NKS
>>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>


--
Irwin KD3TB
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Re: KPA500 finals blown

Michael Cozzi

     Irwin,

     There's an easy modification you could do that might net 4-5c
reduction in temperature.

     On the top of the amp install an additional matching fan blowing
*in* through the intake. One could conceivably wire it to the fan power
on the amp (though I would check what max draw is for that circuit).
This will increase the air velocity, turbulence, and the CFM of the
entire cooling chain.

     Learned this little trick working with computer water cooling. Was
trying to keep a 220w TDP processor below 50c under load. If you can't
get more surface area on a heat sink or radiator- increasing CFM and air
turbulence can make a big difference.

     Michael KD8TUT

On 1/21/2016 11:26 AM, Irwin Darack wrote:

> In discussions with Elecraft at Dayton, we should be able to run the KPA500
> at 300 watts during a RTTY contest. This would include Running versus S/P.
> The fans on mine do come on high and I keep an eye on the temp reading. I
> do need to stop occasionally to allow the amp to cool down. I am not sure
> if there is a way to add an addition external fan to increase the air flow?
>
> Irwin KD3TB
>
> On Thursday, January 21, 2016, Phil Wheeler <[hidden email]> wrote:
>
>> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 minutes
>> key down / 5 minutes standby" seems pretty definitive for normal
>> operations, even RTTY, Earl.
>>
>> 73, Phil W7OX
>>
>> On 1/21/16 6:44 AM, efortner wrote:
>>
>>> I would like to know what the continous keydown power output rating is.
>>> The
>>> manual talks about ICAS. I know when I get on RTTY I does not take long
>>> for
>>> The fans to come up to full speed running 300 watts.
>>>
>>> Earl, K4Kay
>>>
>>> -----Original Message-----
>>> From: Elecraft [mailto:[hidden email]] On Behalf Of
>>> Nand
>>> Kishore
>>> Sent: Thursday, January 21, 2016 4:29 AM
>>> To: elecraft
>>> Subject: [Elecraft] KPA500 finals blown
>>>
>>> KPA500 shut off with a bang while operating RTTY @300W.
>>>
>>> Antenna is a steppir beam.
>>>
>>> On opening the KPA500,found 2 ceramic? caps of VRF2933
>>> adrift with underside of the said caps,black.
>>>
>>> Have written to support.Is this the first time this has happened
>>> in a KPA500?
>>>
>>> 73 and HNY,
>>> Nandu
>>> VU2NKS
>>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>>
>

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Re: KPA500 finals blown

Clay Autery
In reply to this post by Irwin Darack
Thermal design and supplementation of existing designs is not often a
trivial task.  To do it properly, requires a well-reasoned, step-by-step
plan that is both scientifically and mathematically driven AND limited.
One cannot break the laws of physics...  you can sometimes appear to
bend them, but you can't break 'em.

And on a fine piece of equipment like the KPA500, it would be all but
criminal NOT to do it right.  I've not had the privilege to see the
inside of one yet, but I do have a great deal of experience solving
thermal control problems.

Contact me offline if you're serious about this AND you have verified
that the amp is 100% operational and performing within specs.  Thermal
design is not a band-aid for ailing equipment.

73,

______________________
Clay Autery

On 1/21/2016 10:26 AM, Irwin Darack wrote:
> I am not sure
> if there is a way to add an addition external fan to increase the air flow?

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Re: KPA500 finals blown

Clay Autery
In reply to this post by Michael Cozzi
Not a bad tip...  Additionally, IF you make sure your input fan has some
sort of filtering device on it, AND that as filtered produces 25%+ more
CFM than the exhaust fan, you will have a VERY slightly positive
pressured chassis which will assist in keeping the internals dust and
dirt free.

Don't make the mistake of just increasing the flow rate of an exhaust
fan...  Might help, but it will cause a slightly NEGATIVE internal
pressure which will overrun the intake vents and start sucking all
manner of grunge into the machine via every available crack and
crevice...  jacks, USB ports, chassis edges, etc.

The less dirt inside, especially on heat sinks, the better.

But again...  first step is to make SURE the unit is healthy and
performing within specs.

73,

______________________
Clay Autery

On 1/21/2016 11:13 AM, Michael Cozzi wrote:
> On the top of the amp install an additional matching fan blowing *in*
> through the intake. One could conceivably wire it to the fan power on
> the amp (though I would check what max draw is for that circuit). This
> will increase the air velocity, turbulence, and the CFM of the entire
> cooling chain.

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Re: KPA500 finals blown

k6dgw
In reply to this post by Phil Wheeler-2
Well ... it says that, in any 15 minute interval, you can be key-down
continuously for 10 minutes followed by key-up for 5 minutes which looks
like a 0.66 duty cycle on my slide rule.  Presumably, this could be
followed by another such sequence.

Is 10 min down/5 min up repeatedly the same as 40 sec down/20 sec up
repeatedly?  Intuitively, it seems to me that the PA-heatsink will come
to some equilibrium temp and a 10m D/5m U duty cycle may not yield the
same final temp as a 60s D/20s U duty cycle.  Then again, I struggled
through Thermodynamics.

I know the original KPA500 field testers were encouraged to run the amp
at "full bars."

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 1/21/2016 7:53 AM, Phil Wheeler wrote:
> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10
> minutes key down / 5 minutes standby" seems pretty definitive for normal
> operations, even RTTY, Earl.
>
> 73, Phil W7OX

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Re: KPA500 finals blown

Jim AB3CV
I've run echo tests on 6m EME for hours at a time which is 50% duty cycle
and 500w+.

I always run RTTY contests at 500+.

Yes the fans get going. That's what they're supposed to do. But I've never
had a problem.

73

jim ab3cv



On Thu, Jan 21, 2016 at 1:12 PM, Fred Jensen <[hidden email]> wrote:

> Well ... it says that, in any 15 minute interval, you can be key-down
> continuously for 10 minutes followed by key-up for 5 minutes which looks
> like a 0.66 duty cycle on my slide rule.  Presumably, this could be
> followed by another such sequence.
>
> Is 10 min down/5 min up repeatedly the same as 40 sec down/20 sec up
> repeatedly?  Intuitively, it seems to me that the PA-heatsink will come to
> some equilibrium temp and a 10m D/5m U duty cycle may not yield the same
> final temp as a 60s D/20s U duty cycle.  Then again, I struggled through
> Thermodynamics.
>
> I know the original KPA500 field testers were encouraged to run the amp at
> "full bars."
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the Cal QSO Party 1-2 Oct 2016
> - www.cqp.org
>
> On 1/21/2016 7:53 AM, Phil Wheeler wrote:
>
>> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10
>> minutes key down / 5 minutes standby" seems pretty definitive for normal
>> operations, even RTTY, Earl.
>>
>> 73, Phil W7OX
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
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Re: CESSB Duty Cycle

Joe Subich, W4TV-4
In reply to this post by wayne burdick

> That said, we will be playing with this in DSP code to see if it's
> worth the trouble.

In theory it should be worth the trouble as the distortion (other than
any increased background noise) should be less than typical "hard"
clipping with a non-phase equalized filter (for the K3, that's the
KFL3B-2.7 or KFL3B-2.8).  Put another way, the user should be able to
clip "harder" with less distortion using the CESSB algorithm.

73,

    ... Joe, W4TV


On 1/21/2016 10:39 AM, Wayne Burdick wrote:

> The finals could handle it, just as they handle full-carrier modes
> like RTTY and FM. The bigger problem, specifically described in the
> article, is the power supply. Many operators who use SSB or CW only,
> not full-carrier modes, are using power supplies that are barely
> adequate. They can handle 20+ amps at light duty cycle, but not
> CESSB, etc.
>
> As I mentioned previously, both the K3/K3S and KX3 have excellent
> speech compression already, and the difference between a fairly
> aggressive compression setting and CESSB is, in practice, rarely
> going to make a difference. That said, we will be playing with this
> in DSP code to see if it's worth the trouble.
>
> Wayne N6KR
>
>
>
> On Jan 21, 2016, at 6:56 AM, Bob McGraw K4TAX <[hidden email]>
> wrote:
>
>> The recent article in February QST describing the CESSB mode is of
>> interest.  Just wondering if that mode can or will be added to the
>> code operating the K3S?   Also, wondering if the higher duty cycle
>> of the CESSB mode will exceed the ratings of the PA stage and that
>> of the KPA500?  From what I read it seems that most SSB rated amps,
>> past and present,  may have inadequate ratings for the higher duty
>> cycle.
>>
>> Thoughts?
>>
>> 73 Bob, K4TAX
>
>
>
> ______________________________________________________________
> 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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Re: KPA500 finals blown

Eric Swartz - WA6HHQ
Administrator
In reply to this post by Jim AB3CV
The KPA500 will automatically go into standby if it feels it is getting too hot.
This is done with a safety margin between that temperature and the max operating
temp for the PA's.

Its perfectly OK to operate it at the full fan speed. We expect it to go there
in normal higher duty cycle operation.

73,

Eric
/elecraft.com/

On 1/21/2016 10:20 AM, Jim Miller wrote:

> I've run echo tests on 6m EME for hours at a time which is 50% duty cycle
> and 500w+.
>
> I always run RTTY contests at 500+.
>
> Yes the fans get going. That's what they're supposed to do. But I've never
> had a problem.
>
> 73
>
> jim ab3cv
>
>
>
> On Thu, Jan 21, 2016 at 1:12 PM, Fred Jensen <[hidden email]> wrote:
>
>> Well ... it says that, in any 15 minute interval, you can be key-down
>> continuously for 10 minutes followed by key-up for 5 minutes which looks
>> like a 0.66 duty cycle on my slide rule.  Presumably, this could be
>> followed by another such sequence.
>>
>> Is 10 min down/5 min up repeatedly the same as 40 sec down/20 sec up
>> repeatedly?  Intuitively, it seems to me that the PA-heatsink will come to
>> some equilibrium temp and a 10m D/5m U duty cycle may not yield the same
>> final temp as a 60s D/20s U duty cycle.  Then again, I struggled through
>> Thermodynamics.
>>
>> I know the original KPA500 field testers were encouraged to run the amp at
>> "full bars."
>>
>> 73,
>>
>> Fred K6DGW
>> - Northern California Contest Club
>> - CU in the Cal QSO Party 1-2 Oct 2016
>> - www.cqp.org
>>
>> On 1/21/2016 7:53 AM, Phil Wheeler wrote:
>>
>>> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10
>>> minutes key down / 5 minutes standby" seems pretty definitive for normal
>>> operations, even RTTY, Earl.
>>>
>>> 73, Phil W7OX
>>>
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Re: KPA500 finals blown

alorona
In reply to this post by Irwin Darack
Holy smokes. If the ceramic was actually blown off of the transistor packages (!), be careful not to inhale any ceramic dust that may be present. That's beryllium oxide which is quite toxic in dust form.
Al  W6LX
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Re: KPA500 finals blown

ab2tc
Hi,

I had thought the use of beryllium oxide had been discontinued as the insulator for RF power transistors, but no such luck: Here is the safety note from Microsemi's data sheet:

"HAZARDOUS MATERIAL WARNING: The ceramic portion of the device below the lead plane is beryllium oxide. Beryllium oxide dust is highly toxic when inhaled. Care must be taken during handling and mounting to avoid damage to this area. These devices must never be thrown away with general industrial or domestic waste. BeO substrate weight: 0.703g. Percentage of total module weight which is BeO: 9%."

AB2TC - Knut

alorona wrote
Holy smokes. If the ceramic was actually blown off of the transistor packages (!), be careful not to inhale any ceramic dust that may be present. That's beryllium oxide which is quite toxic in dust form.
Al  W6LX
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Re: KPA500 finals blown

mcduffie
In reply to this post by Irwin Darack
On Thu, 21 Jan 2016 11:26:27 -0500, Irwin Darack wrote:

> The fans on mine do come on high and I keep an eye on the temp reading. I
> do need to stop occasionally to allow the amp to cool down. I am not sure
> if there is a way to add an addition external fan to increase the air flow?

I don't have any comparison between mine and others.  However, I can offer a few
points about how mine runs.

I use the amp at pretty much full power for meteor scatter modes (digital) on
six meters daily.  I have found two things.  First, temperature does depend on
the antenna.  Even though the VSWR on the KPA indicates 1.0 for all directions
that I point the antenna, the heat is higher in some directions than others. You
can bet that higher SWR will cause the fan to run more than a perfect match.

Second, if I keep the transmit/receive sequences down to 15 seconds each (JT9g
or h, JTMSK, ISCAT), I rarely hit fan speed 5.  It cycles as high as 4 every
cycle after initial warm up.  These on and off cycles (50% duty cycle) can
continue for from a few minutes to an hour or more for one completed QSO with
only an occasional excursion to fan speed 5.

When I point to the southeast, the fan steps on up to speed 5 almost every other
transmission period.

On some modes that have longer transmit cycles, like FSK 441 with ~45 seconds on
and one minute off, the fan regularly steps up to 6 after the initial few
cycles.  Step 6 always comes into play for me during those longer transmissions
on six meters.

I've found that I can reduce the heat cycle a little (noticeably) by using a
small fan 2-3 feet away on the right side, blowing at the hot spot on the right
rear side of the cover (this is the side panel, not the rear panel).  It doesn't
take much air, but it does reduce the high speed cycles.

All of this is on six meters.  Six meters generates more heat than HF.  I never
come above speed 4 (usually 3 at the most) on ten meters and below.

Just because I like to be conservative and strongly dislike heat in solid state
devices, I typically manually put the fan on speed 4 when I start a digital
exchange and back to NORmal when done.  That alone, keeps it from hitting speed
5 most of the time.

Drive power for all of this is 27 watts from my xcvr (at least that's what it is
set at and is likely slightly less).  Power fades to lower than 450 watts on
some modes when it is hot, but that could be the xcvr.  Most solid state devices
fade power when they get hot.  Some modes run slightly less power, but that's
more a function of the audio frequencies being used for the mode and response of
the radio.

Anyway, that's my story, and I'm stickin' to it.  :)

Love my KPA!

Gary - AG0N
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Re: KPA500 finals blown

mcduffie
In reply to this post by k6dgw
On Thu, 21 Jan 2016 10:12:08 -0800, Fred Jensen wrote:

> I know the original KPA500 field testers were encouraged to run the amp
> at "full bars."

I had also heard that, and it was run on RTTY at up to 700W during a contest.

Gary - AG0N
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