KPA-1500 fan speeds and fan noise

[Elecraft mailing list]

I think the KPA-1500 is a very nice amplifier and am happy to won one.  That said, I'd like to see Elecraft find ways to reduce the fan noise, and I believe there are solutions, such as: in "Fan 1" mode: rather than have Fan 1 turn on at full speed with full noise, I'd much prefer to have all 3 fans turn on and run at 1/3 speed as the noise should be reduced while the air flow would be about the same.  When the 3 similarly sized fans on my Yaesu Quadra run at slow speed while the amp is in stand-by or receive mode they are pretty quiet and only generate about the same amount of noise as many desktop computers, and when the Quadra is transmitting the fans go to high speed and produce about the same amount of noise as the KPA-1500 when it's running in the "Fan 2" position.  I imagine Fan positions 3-4-5 are needed because the heat sink in the KPA-1500 is relatively small because the physical size of the amp is small?
 
73,
Dick- K9OM
 
 
 
 
  
 
 
 
 
 
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[Clay Autery-2]

Are they 80 or 92mm fans?

You are correct....  You can realize the same volume of air delivery at
lower noise levels by running 2 or more fans slower. Increasing the
intake area for the same volume of flow reduces pressure, turbulence,
noise... lots of cool stuff.  :)

I'm  not sure what the hardware circuit looks like and how much
flexibility they have for controlling the fans, but this would be one
way to stave off the noise for a while...

______________________
Clay Autery, KY5G
[phone]

On 05/20/18 18:12, Dick via Elecraft wrote:

> I think the KPA-1500 is a very nice amplifier and am happy to won one.  That said, I'd like to see Elecraft find ways to reduce the fan noise, and I believe there are solutions, such as: in "Fan 1" mode: rather than have Fan 1 turn on at full speed with full noise, I'd much prefer to have all 3 fans turn on and run at 1/3 speed as the noise should be reduced while the air flow would be about the same.  When the 3 similarly sized fans on my Yaesu Quadra run at slow speed while the amp is in stand-by or receive mode they are pretty quiet and only generate about the same amount of noise as many desktop computers, and when the Quadra is transmitting the fans go to high speed and produce about the same amount of noise as the KPA-1500 when it's running in the "Fan 2" position.  I imagine Fan positions 3-4-5 are needed because the heat sink in the KPA-1500 is relatively small because the physical size of the amp is small?
>  
> 73,
> Dick- K9OM
>  
>  
>  
>  
>    
>  
>  
>  
>  
>  
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[Roy Koeppe]

All,

My solution is two 4.5-inch, 48-volt dc muffin fans sitting on half-inch
tall rubber feet covering the top exhaust vent on amp. They are running on a
19-volt supply at a slow but effective cooling speed and are very quiet
(drawing air upward). During normal CW rag chewing the main fans do not come
on -- a vast improvement for a few bucks. When you go portable, just leave
'em home.

73,    Roy         K6XK












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[Elecraft mailing list]

 That doesn't move any air across the heat sink or solid state devices that need the air.  The air that comes out of those vents starts at the fans in the rear.
BillK3WJV

    On Monday, May 21, 2018, 6:07:22 AM EDT, Roy Koeppe <[hidden email]> wrote:  
 
 All,

My solution is two 4.5-inch, 48-volt dc muffin fans sitting on half-inch
tall rubber feet covering the top exhaust vent on amp. They are running on a
19-volt supply at a slow but effective cooling speed and are very quiet
(drawing air upward). During normal CW rag chewing the main fans do not come
on -- a vast improvement for a few bucks. When you go portable, just leave
'em home.

73,    Roy        K6XK












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[ANDY DURBIN]

From the KPA500 kit build manual:

"If airflow arrows are visible on the fan housing, they will show that air will be blown out of the back of the KPA500."


It was a bit surprising to me that the KPA500 fan airflow is the opposite of natural convective flow but I accepted that was the intended design.  My KPA500 fan does pull air in the top and exhaust it out of the back.


"They are running on a 19-volt supply at a slow but effective cooling speed and are very quiet (drawing air upward)."


Do the KPA1500 fans push air into the box? If so, why doesn't the KPA500 fan do that. If the KPA1500 fans pull out of the box why would it be appropriate to use an additional fan that opposes this airflow?


73,

Andy k3wyc
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[Ed Gray W0SD]

I have a KPA-1500  #171 and when I set the fans at 1 the air is being
pulled from the back by only the middle fan on  the back. The air is
exiting out the top cover, front, right.  This exit area is just a
little over 5" x 8".  I feel a good deal of air coming out the top
evenly distributed over the 5" x 8" area.

Set at position 2, 3, 4 and 5 all three fans run and the fan speed is
increased with each setting.  2 is IMHO is not very noisy, 3 is more
noise than I like if ran continuously. Sporadically would be OK assuming
it would not be needed a lot. 4 and especially 5 are noisy.  However I
would think you would only need 4 or 5 with lots of TX in RTTY or WSJT
modes so one would not need to be concerned about mic pick up however I
will say 4 and 5 are not pleasant to listen to.  More to be learned by
me but I suspect letting the fan be regulated by the temperature rather
than a fixed setting may be the way to go for lots of TX in RTTY or WSJT.

Anyway the air comes in the back and goes out the top cover on the KPA-1500.

Ed W0SD



On 5/21/2018 9:13 AM, ANDY DURBIN wrote:

> >From the KPA500 kit build manual:
>
> "If airflow arrows are visible on the fan housing, they will show that air will be blown out of the back of the KPA500."
>
>
> It was a bit surprising to me that the KPA500 fan airflow is the opposite of natural convective flow but I accepted that was the intended design.  My KPA500 fan does pull air in the top and exhaust it out of the back.
>
>
> "They are running on a 19-volt supply at a slow but effective cooling speed and are very quiet (drawing air upward)."
>
>
> Do the KPA1500 fans push air into the box? If so, why doesn't the KPA500 fan do that. If the KPA1500 fans pull out of the box why would it be appropriate to use an additional fan that opposes this airflow?
>
>
> 73,
>
> Andy k3wyc
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>

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[Roy Koeppe]

Yes it does, normally air flow is from rear to top. The fans placed over the
exhaust vent on top create a partial vacuum, drawing in air through the idle
(or running) fans on the rear apron and out the top just like when the
regular fans are doing that job.

Roy    K6XK


"That doesn't move any air across the heat sink or solid state devices that
need the air.  The air that comes out of those vents starts at the fans in
the rear."
BillK3WJV

    On Monday, May 21, 2018, 6:07:22 AM EDT, Roy Koeppe <[hidden email]>
wrote:

All,

My solution is two 4.5-inch, 48-volt dc muffin fans sitting on half-inch
tall rubber feet covering the top exhaust vent on amp. They are running on a
19-volt supply at a slow but effective cooling speed and are very quiet
(drawing air upward). During normal CW rag chewing the main fans do not come
on -- a vast improvement for a few bucks. When you go portable, just leave
'em home.

73,    Roy        K6XK



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[Elecraft mailing list]

 If you are going to depend on those 2 fans sucking hot air out of the amp instead of using the internal fans that push it where it needs to go, I think you arepulling hot air out of the amp and that hot air has already done its damage.
BillK3WJV

    On Monday, May 21, 2018, 3:29:29 PM EDT, Roy Koeppe <[hidden email]> wrote:  
 
 Yes it does, normally air flow is from rear to top. The fans placed over the
exhaust vent on top create a partial vacuum, drawing in air through the idle
(or running) fans on the rear apron and out the top just like when the
regular fans are doing that job.

Roy    K6XK


"That doesn't move any air across the heat sink or solid state devices that
need the air.  The air that comes out of those vents starts at the fans in
the rear."
BillK3WJV

    On Monday, May 21, 2018, 6:07:22 AM EDT, Roy Koeppe <[hidden email]>
wrote:

All,

My solution is two 4.5-inch, 48-volt dc muffin fans sitting on half-inch
tall rubber feet covering the top exhaust vent on amp. They are running on a
19-volt supply at a slow but effective cooling speed and are very quiet
(drawing air upward). During normal CW rag chewing the main fans do not come
on -- a vast improvement for a few bucks. When you go portable, just leave
'em home.

73,    Roy        K6XK



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[ke9uw]

Seems like if the internal fans don't go on, that means the fan on the top is cooling the amp.

Chuck Hawley
 [hidden email]

 Amateur Radio, KE9UW
 aka Jack, BMW Motorcycles
________________________________________
From: [hidden email] [[hidden email]] on behalf of Bill Stravinsky via Elecraft [[hidden email]]
Sent: Monday, May 21, 2018 8:01 AM
To: Elecraft Reflector
Subject: Re: [Elecraft] KPA1500 fan speeds and fan noise

 That doesn't move any air across the heat sink or solid state devices that need the air.  The air that comes out of those vents starts at the fans in the rear.
BillK3WJV

    On Monday, May 21, 2018, 6:07:22 AM EDT, Roy Koeppe <[hidden email]> wrote:

 All,

My solution is two 4.5-inch, 48-volt dc muffin fans sitting on half-inch
tall rubber feet covering the top exhaust vent on amp. They are running on a
19-volt supply at a slow but effective cooling speed and are very quiet
(drawing air upward). During normal CW rag chewing the main fans do not come
on -- a vast improvement for a few bucks. When you go portable, just leave
'em home.

73,    Roy        K6XK












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[Elecraft mailing list]

 Feel free to do that with your kpa1500.  While you're at it test how long it takes to reach 60C with and without the modified fan system.I'm comfy with hearing the fans come on and I even set the fan speed to 1 or 2 if I'm in a contest mode.  I don't think there's a thing astoo much cooling for a solid state amp running 1500 watts.  The brief time I've played with mine it doesn't take too long to get to 60Cif you xmit enough.
Good luck.
BillK3WJV

    On Monday, May 21, 2018, 5:11:01 PM EDT, hawley, charles j jr <[hidden email]> wrote:  
 
 Seems like if the internal fans don't go on, that means the fan on the top is cooling the amp.

Chuck Hawley
 [hidden email]

 Amateur Radio, KE9UW
 aka Jack, BMW Motorcycles
________________________________________
From: [hidden email] [[hidden email]] on behalf of Bill Stravinsky via Elecraft [[hidden email]]
Sent: Monday, May 21, 2018 8:01 AM
To: Elecraft Reflector
Subject: Re: [Elecraft] KPA1500 fan speeds and fan noise

 That doesn't move any air across the heat sink or solid state devices that need the air.  The air that comes out of those vents starts at the fans in the rear.
BillK3WJV

    On Monday, May 21, 2018, 6:07:22 AM EDT, Roy Koeppe <[hidden email]> wrote:

 All,

My solution is two 4.5-inch, 48-volt dc muffin fans sitting on half-inch
tall rubber feet covering the top exhaust vent on amp. They are running on a
19-volt supply at a slow but effective cooling speed and are very quiet
(drawing air upward). During normal CW rag chewing the main fans do not come
on -- a vast improvement for a few bucks. When you go portable, just leave
'em home.

73,    Roy        K6XK












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[ANDY DURBIN]

Bob,


I have made no changes to the cooling of my KPA500.  I also have no idea to what extent the designers of the KPA500 studied the thermodynamics of the design.   I have, however, been surprised at how quickly it heats up.    I abandoned a heating test with the amplifier only producing 100 W output when the PA temperature reached 70 deg C after only 1 minute 45 seconds.  At that point the temperature was close to asymptotic and fan speed was 5 so it may not have gone much higher.


My KPA500 seems horribly inefficient when compared to my TS-590S running a similar power output.  The data for the heating test showed a PA efficiency of 23%, far short of the "approximately 50%" stated in the specification.


I'm willing to share my test data but I know of no means to post it on this stone age "reflector".


73,

Andy k3wyc


________________________________
From: Bob McGraw K4TAX <[hidden email]>
Sent: Monday, May 21, 2018 6:57 PM
To: ANDY DURBIN
Subject: Re: [Elecraft] KPA1500 fan speeds and fan noise

Andy:

There are basically two types of radial blade fans and specific
application for each one.   Those that "blow" and those that "suck".
There is a difference in the design of the fan blades and the
application for a specific fan.   Also some are designed to have "air
over the motor".  This is a point affecting motor life and bearing
lubrication.

Those that "blow" are designed to pressurize a box or enclosure to a
specific  pressure measured in inches or millibars of H²O. Reducing the
air exhaust area or restricting air exhaust flow, thus increasing
internal pressure, can cause a blade stall.  This actually reduces the
amount of air measured in CFM that a given fan can deliver.

The other type  of fan, those that "suck" are designed to exhaust air
from a box or enclosure to a specific value measured in inches or
millibars of H²0.     There is always some amount of restriction to
airflow entering, usually being contributed by the obstruction i.e. air
vents,  to air entering the box.  The perforated air vent on top of the
KPA500 as an example.

While I agree that increased airflow is beneficial to keeping
electronics cool, one must assure that added cooling efforts do not
create a vortex in the given area to be cooled.   This could cause a
void of air movement and thus reduced cooling.    The KPA500 {I can't
speak for the KPA1500} are surely engineered and evaluated {brick on the
key}  to work within design limits of the solid state devices along with
cooling other components.    In some cases, ones added cooling efforts
which may actually cause a partial blade stall, same as the stall effect
of an airplane wing, and thus cooling is actually reduced and, in many
cases.  In some instances, overall fan noise being increased.

Take care in the application of added cooling efforts.

I run my KPA500 with the FAN CTL at Normal.   It will step through all 6
levels as needed, otherwise it is off.    I find no reason for it to run
all of the time at the lowest speed. Depending on mode and length of
transmission, I find the fan comes on and will ramp up as needed.
I've not seen any reported temperature above 65ºC with a heat sink upper
limit of 90ºC.

73

Bob, K4TAX



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[K9MA]

On 5/21/2018 23:18, ANDY DURBIN wrote:
> My KPA500 seems horribly inefficient when compared to my TS-590S running a similar power output.  The data for the heating test showed a PA efficiency of 23%, far short of the "approximately 50%" stated in the specification.

That's perfectly normal at that low power output.  The 50% spec is at
full output.  If you ran your TS-590S at 20 W output, you would probably
see about the same low efficiency.

73,

Scott K9MA

--
Scott  K9MA

[hidden email]

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[Charlie T, K3ICH]

Yes, if you want to run QRP/battery, you are fooling yourself if you crank ANY * 100 watt radio down to 10 watts out.

Same with, for example, the TS-480, 200 watt version. It's efficiency, even at 100 watts out is barely 25%
The signal is probably cleaner, but the efficiency is shot.

73, Charlie k3ICH

*the K3 is the exception since it bypasses the 100W amp when you go LOW (smart radio eh?).

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of K9MA
Sent: Tuesday, May 22, 2018 1:07 AM
To: [hidden email]
Subject: Re: [Elecraft] KPA500 cooling and efficiency

On 5/21/2018 23:18, ANDY DURBIN wrote:
> My KPA500 seems horribly inefficient when compared to my TS-590S running a similar power output.  The data for the heating test showed a PA efficiency of 23%, far short of the "approximately 50%" stated in the specification.

That's perfectly normal at that low power output.  The 50% spec is at full output.  If you ran your TS-590S at 20 W output, you would probably see about the same low efficiency.

73,

Scott K9MA

--
Scott  K9MA

[hidden email]

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[ANDY DURBIN]

"That's perfectly normal at that low power output.  The 50% spec is at full output."


Thanks for pointing that out. I did a spot check on the same band with KPA500 indicated output of 490 W (LP-100A 500W) and found the efficiency was 60.6%  (61.9% if LP-100A power is used).


73,

Andy k3wyc

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