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Dave KD1NA

KPA 500

Everyone,

I have had my KPA500 linear for some time now and have been really happy
with it. I use it with my K3 and they communicate with each other via the
DB15 AUX cable that I built ( the one furnished by Elecraft was too short).

The only issue I have encountered is the finals in the linear seem to heat
up rather quickly causing the fan to kick in in a rather short period of
time. it doesn't matter if I use the dummy load or a good match antenna. I
also noticed the finals seem to cool rather quickly after the transmittion
is terminated and the fan turns on after about 30 seconds to one minute
after starting a ssb transmittion then goes to a higher speed after about
30 seconds more. If my transmittion time is greater then 2 to 3 minutes the
fans go to high and the final temperature is around 70 degrees C. I have
never had the linear go in to a fault because of heat.

The fix.

I removed the top, front, and right side panels of the KPA500. When I first
built the linear I realized the mounting screws that mount the Z panel to
the amplifier module were too long so I used the shorter ones that would
normally go to mount the top panel. On inspecting these screws they were
tight. Looking at the right panel I noticed there are 4 screws that mount
the panel directly to the amplifier's heat sink. They were not as tight as
I would have liked. I wanted to get the most efficient heat transfer from
the module so I carefully applied some heat sink compound to the side of
the heat sink of the amplifier module before carefully mounting the right
sied panel back on the amplifier. I carefully made sure the 4 screws that
mount from the panel to the heatsink ( which are normally covered by the
handle) were solidly and carefully tightened. After inspecting the
transformer connections and the rest of the inside of the linear I
reassembled it and tested it out.

Findings.

Now when I am running ssb typically the fan doesn't come on until well in
to the qso and never has the fan reach high mode. If I brick the key at 500
watts into a dummy load the fan goes high after about 2 minutes. I also
noted the finals heat up slower and cool slower and the left panel
temperature follows the final temperature..

Now the amp seems very happy and I am not bugged by the constant fan noise
during a qso.

I thought I would pass this on to everyone.

Thanks and 73
Dave KD1NA
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Guy, K2AV

Re: KPA 500

My question is whether you actually increased the no-fan heat dissipation
of the heat sink complex that significantly, or whether what you did is
faking out the heat sensor and causing the fan to NOT come on when it
actually should.

It bothers me also that the increased dissipation is non-symetrical, and
will cause one side of the heat sink to be at a different temperature than
the other. This is a bad situation that theoretically can damage
transistors by putting unequal mechanical stress on the mounting in high
heat situations. It also could cause one transistor to be a lot hotter
than the other. Or it COULD be that what you did equalized heat
distribution. The problem is that YOU DON'T KNOW WHICH ONE.

Fan speed, when it comes on, size of heat sink, etc and the transistors
used are a very carefully engineered COMBO. I really would not screw
around with it UNTIL you have discussed it with the Elecraft engineer and
have his concurrence. There is a lot more here than meets the eye. Be
very careful what you recommend to other owners. Elecraft please weigh in
before this gets around as an ill-advised urban myth, if indeed it is
ill-advised.

Beyond that, why is everyone so aroused by fan speed? Fans keep things
cool. Fans are good.

My roaring 100 CFM monster fan on my contest 3-1000Z amp, my
"Loudenboomer," keeps me from melting it when I qsy all over the band and
don't remember to retune it. I get pretty stupid late into a contest.
Roaring fan makes 3-1000Z last long time. 3-1000Z getting expensive and
hard to find. Roaring fan is my friend. Need to use headset anyway for
best diversity on 160. Use noise cancelling headset, can't hear the roar.

Fans are your friend.

73, Guy.

On Mon, Jun 18, 2012 at 7:42 AM, David Robertson <[hidden email]> wrote:

> Everyone,
>
> I have had my KPA500 linear for some time now and have been really happy
> with it. I use it with my K3 and they communicate with each other via the
> DB15 AUX cable that I built ( the one furnished by Elecraft was too short).
>
> The only issue I have encountered is the finals in the linear seem to heat
> up rather quickly causing the fan to kick in in a rather short period of
> time. it doesn't matter if I use the dummy load or a good match antenna. I
> also noticed the finals seem to cool rather quickly after the transmittion
> is terminated and the fan turns on after about 30 seconds to one minute
> after starting a ssb transmittion then goes to a higher speed after about
> 30 seconds more. If my transmittion time is greater then 2 to 3 minutes the
> fans go to high and the final temperature is around 70 degrees C. I have
> never had the linear go in to a fault because of heat.
>
> The fix.
>
> I removed the top, front, and right side panels of the KPA500. When I first
> built the linear I realized the mounting screws that mount the Z panel to
> the amplifier module were too long so I used the shorter ones that would
> normally go to mount the top panel. On inspecting these screws they were
> tight. Looking at the right panel I noticed there are 4 screws that mount
> the panel directly to the amplifier's heat sink. They were not as tight as
> I would have liked. I wanted to get the most efficient heat transfer from
> the module so I carefully applied some heat sink compound to the side of
> the heat sink of the amplifier module before carefully mounting the right
> sied panel back on the amplifier. I carefully made sure the 4 screws that
> mount from the panel to the heatsink ( which are normally covered by the
> handle) were solidly and carefully tightened. After inspecting the
> transformer connections and the rest of the inside of the linear I
> reassembled it and tested it out.
>
> Findings.
>
> Now when I am running ssb typically the fan doesn't come on until well in
> to the qso and never has the fan reach high mode. If I brick the key at 500
> watts into a dummy load the fan goes high after about 2 minutes. I also
> noted the finals heat up slower and cool slower and the left panel
> temperature follows the final temperature..
>
> Now the amp seems very happy and I am not bugged by the constant fan noise
> during a qso.
>
> I thought I would pass this on to everyone.
>
> Thanks and 73
> Dave KD1NA
> ______________________________________________________________
> 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
>

Donehrlich@q.com

KPA 500 Fan Noise and cooling performance

In reply to this post by Dave KD1NA

On 6/18/2012 4:42 AM, David Robertson wrote: ( ... a long message I
won't include here where he improved amplifier cooling by tightening
heatsink/right panel screws and used heatsink compound.)

I operate my KPA500 with the fan speed set to #1 continuously which
delays the increase in the increase in fan speed once the amplifier
starts putting out power. My amplifier did not exceed 58 deg C after 10
minutes at 500 watts carrier output into a dummy load and it stabilized
at about 60 degrees in a 25 degree C room. My right panel to heatsink
screws (the ones under the handle) were all tight and that explains why
my experience was better than was Dave's originally before he tightened
his heatsink screws and added heatsink compound. I then added heatsink
compound to the mating surface between my heatsink and the right side
panel. There was no difference in cooling performance at all. I just
wanted to know .. and now I do .. and so do you.

The KPA500 fan is as quiet as any muffin fan ought to be but it was
still annoying to me. That is not an amplifier fault .. it is just that
I have good hearing and I prefer a *very quiet shack. For those who may
be like me in that regard here is how I reduced the normal fan noise of
my amplifier. In my amplifier much of the fan noise was actually coming
from the sheet metal of the amplifier structure which was being excited
by the vibration of the fan which is rigidly attached to the amplifier
structure so that fan vibration was communicated to the structure which
then resonated and amplified the fan noise. When I removed the fan and
held it loosely in my hand while it was running I could feel the light
high frequency 'buzz' produced by the rotating magnetic field of the fan
and also, crucially, the lower frequency throb caused by a slight weight
imbalance in the rotor. I used a small piece of sticky pad (normally
used to mount components to a chassis, etc) and placed this very small
weight at various points on the rotor blades until, by trial and error,
found the 'sweet' spot which resulted in greatly reduced throb. That
reduced fan noise considerably.

Then, to reduce transmission of fan vibration to the amplifier structure
even further, I mounted the fan loosely to the back of the amplifier
using soft quarter-inch cushions between the fan and the amplifier. I
used light wire to do the actual attachment instead of the long screws
that are standard. The overall effect is considerably less fan noise
and I am very happy about that. The fan mounting is fragile and not to
be recommended if the amplifier is to be moved very much but in my
installation it is just fine. By the way, I carefully compared cooling
performance before and after the fan mounting modification and found no
difference at all. I also noticed during my testing that the direction
of airflow makes no difference.

Don K7FJ

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w0mu

Re: KPA 500

In reply to this post by Guy, K2AV

The fan rarely ever kicks in for me. My QSO's are pretty short. DX,
contests. The only time I have really seen the fans go on is with
RTTY. To it sounds like the OP has or had a problem with the initial
build. If the screws were loose that secured the heat sink panel I
could see that being problematic.

When in J6 we upped the fan speed on the outset to about 3 because it
was always 80 degrees plus and very humid so I wanted to keep the air
moving. We ran the CQ WW CW and never had one issue with heat or
anything for that matter.

Mike W0MU

W0MU-1 CC Cluster w0mu.net:23 or w0mu-1.dnsdynamic.com
Http://www.w0mu.com

On 6/18/2012 11:51 AM, Guy Olinger K2AV wrote:

> My question is whether you actually increased the no-fan heat dissipation
> of the heat sink complex that significantly, or whether what you did is
> faking out the heat sensor and causing the fan to NOT come on when it
> actually should.
>
> It bothers me also that the increased dissipation is non-symetrical, and
> will cause one side of the heat sink to be at a different temperature than
> the other. This is a bad situation that theoretically can damage
> transistors by putting unequal mechanical stress on the mounting in high
> heat situations. It also could cause one transistor to be a lot hotter
> than the other. Or it COULD be that what you did equalized heat
> distribution. The problem is that YOU DON'T KNOW WHICH ONE.
>
> Fan speed, when it comes on, size of heat sink, etc and the transistors
> used are a very carefully engineered COMBO. I really would not screw
> around with it UNTIL you have discussed it with the Elecraft engineer and
> have his concurrence. There is a lot more here than meets the eye. Be
> very careful what you recommend to other owners. Elecraft please weigh in
> before this gets around as an ill-advised urban myth, if indeed it is
> ill-advised.
>
> Beyond that, why is everyone so aroused by fan speed? Fans keep things
> cool. Fans are good.
>
> My roaring 100 CFM monster fan on my contest 3-1000Z amp, my
> "Loudenboomer," keeps me from melting it when I qsy all over the band and
> don't remember to retune it. I get pretty stupid late into a contest.
> Roaring fan makes 3-1000Z last long time. 3-1000Z getting expensive and
> hard to find. Roaring fan is my friend. Need to use headset anyway for
> best diversity on 160. Use noise cancelling headset, can't hear the roar.
>
> Fans are your friend.
>
> 73, Guy.
>
> On Mon, Jun 18, 2012 at 7:42 AM, David Robertson<[hidden email]> wrote:
>
>> Everyone,
>>
>> I have had my KPA500 linear for some time now and have been really happy
>> with it. I use it with my K3 and they communicate with each other via the
>> DB15 AUX cable that I built ( the one furnished by Elecraft was too short).
>>
>> The only issue I have encountered is the finals in the linear seem to heat
>> up rather quickly causing the fan to kick in in a rather short period of
>> time. it doesn't matter if I use the dummy load or a good match antenna. I
>> also noticed the finals seem to cool rather quickly after the transmittion
>> is terminated and the fan turns on after about 30 seconds to one minute
>> after starting a ssb transmittion then goes to a higher speed after about
>> 30 seconds more. If my transmittion time is greater then 2 to 3 minutes the
>> fans go to high and the final temperature is around 70 degrees C. I have
>> never had the linear go in to a fault because of heat.
>>
>> The fix.
>>
>> I removed the top, front, and right side panels of the KPA500. When I first
>> built the linear I realized the mounting screws that mount the Z panel to
>> the amplifier module were too long so I used the shorter ones that would
>> normally go to mount the top panel. On inspecting these screws they were
>> tight. Looking at the right panel I noticed there are 4 screws that mount
>> the panel directly to the amplifier's heat sink. They were not as tight as
>> I would have liked. I wanted to get the most efficient heat transfer from
>> the module so I carefully applied some heat sink compound to the side of
>> the heat sink of the amplifier module before carefully mounting the right
>> sied panel back on the amplifier. I carefully made sure the 4 screws that
>> mount from the panel to the heatsink ( which are normally covered by the
>> handle) were solidly and carefully tightened. After inspecting the
>> transformer connections and the rest of the inside of the linear I
>> reassembled it and tested it out.
>>
>> Findings.
>>
>> Now when I am running ssb typically the fan doesn't come on until well in
>> to the qso and never has the fan reach high mode. If I brick the key at 500
>> watts into a dummy load the fan goes high after about 2 minutes. I also
>> noted the finals heat up slower and cool slower and the left panel
>> temperature follows the final temperature..
>>
>> Now the amp seems very happy and I am not bugged by the constant fan noise
>> during a qso.
>>
>> I thought I would pass this on to everyone.
>>
>> Thanks and 73
>> Dave KD1NA
>> ______________________________________________________________
>> 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

Fred Townsend

Re: KPA 500

In reply to this post by Guy, K2AV

Guy: Without putting too fine an edge on it and if I understand David it
seems he has increased the thermal conductivity and thereby decreased the
temperature differential across the heatsink assembly. This reduces thermal
stress and is a good thing and similar to what you strive to do with your
monster fan. The difference is one of finesse and brute force. Because
neither surface area nor air path is affected it is unlikely dissipation is
changed. He is just making better use of the heatsink.
Thermal conductivity, the reciprocal of thermal resistance, has changed.
This resistance is part of a thermal time constant affecting how fast the
fan turns on and off so we should not be surprised the fan turns on and off
at a different rate.
73,
Fred AE6QL

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Guy Olinger K2AV
Sent: Monday, June 18, 2012 10:52 AM
To: David Robertson
Cc: [hidden email]
Subject: Re: [Elecraft] KPA 500

My question is whether you actually increased the no-fan heat dissipation of
the heat sink complex that significantly, or whether what you did is faking
out the heat sensor and causing the fan to NOT come on when it actually
should.

It bothers me also that the increased dissipation is non-symetrical, and
will cause one side of the heat sink to be at a different temperature than
the other. This is a bad situation that theoretically can damage
transistors by putting unequal mechanical stress on the mounting in high
heat situations. It also could cause one transistor to be a lot hotter
than the other. Or it COULD be that what you did equalized heat
distribution. The problem is that YOU DON'T KNOW WHICH ONE.

Fan speed, when it comes on, size of heat sink, etc and the transistors used
are a very carefully engineered COMBO. I really would not screw around with
it UNTIL you have discussed it with the Elecraft engineer and have his
concurrence. There is a lot more here than meets the eye. Be very careful
what you recommend to other owners. Elecraft please weigh in before this
gets around as an ill-advised urban myth, if indeed it is ill-advised.

Beyond that, why is everyone so aroused by fan speed? Fans keep things
cool. Fans are good.

My roaring 100 CFM monster fan on my contest 3-1000Z amp, my "Loudenboomer,"
keeps me from melting it when I qsy all over the band and don't remember to
retune it. I get pretty stupid late into a contest.
Roaring fan makes 3-1000Z last long time. 3-1000Z getting expensive and
hard to find. Roaring fan is my friend. Need to use headset anyway for
best diversity on 160. Use noise cancelling headset, can't hear the roar.

Fans are your friend.

73, Guy.

On Mon, Jun 18, 2012 at 7:42 AM, David Robertson <[hidden email]> wrote:

> Everyone,
>
> I have had my KPA500 linear for some time now and have been really
> happy with it. I use it with my K3 and they communicate with each
> other via the
> DB15 AUX cable that I built ( the one furnished by Elecraft was too
short).

>
> The only issue I have encountered is the finals in the linear seem to
> heat up rather quickly causing the fan to kick in in a rather short
> period of time. it doesn't matter if I use the dummy load or a good
> match antenna. I also noticed the finals seem to cool rather quickly
> after the transmittion is terminated and the fan turns on after about
> 30 seconds to one minute after starting a ssb transmittion then goes
> to a higher speed after about
> 30 seconds more. If my transmittion time is greater then 2 to 3
> minutes the fans go to high and the final temperature is around 70
> degrees C. I have never had the linear go in to a fault because of heat.
>
> The fix.
>
> I removed the top, front, and right side panels of the KPA500. When I
> first built the linear I realized the mounting screws that mount the Z
> panel to the amplifier module were too long so I used the shorter ones
> that would normally go to mount the top panel. On inspecting these
> screws they were tight. Looking at the right panel I noticed there are
> 4 screws that mount the panel directly to the amplifier's heat sink.
> They were not as tight as I would have liked. I wanted to get the most
> efficient heat transfer from the module so I carefully applied some
> heat sink compound to the side of the heat sink of the amplifier
> module before carefully mounting the right sied panel back on the
> amplifier. I carefully made sure the 4 screws that mount from the
> panel to the heatsink ( which are normally covered by the
> handle) were solidly and carefully tightened. After inspecting the
> transformer connections and the rest of the inside of the linear I
> reassembled it and tested it out.
>
> Findings.
>
> Now when I am running ssb typically the fan doesn't come on until well
> in to the qso and never has the fan reach high mode. If I brick the
> key at 500 watts into a dummy load the fan goes high after about 2
> minutes. I also noted the finals heat up slower and cool slower and
> the left panel temperature follows the final temperature..
>
> Now the amp seems very happy and I am not bugged by the constant fan
> noise during a qso.
>
> I thought I would pass this on to everyone.
>
> Thanks and 73
> Dave KD1NA
> ______________________________________________________________
> 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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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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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Guy, K2AV

Re: KPA 500

Actually, he has thermally attached the side panel to the existing heat
sink assembly. I don't know what percentage of the radiating area, but
considering the mass of the heat sink and the confined air flow, IMHO the
change seems exaggerated for just adding a few percent thermal dissipation,
unless it's close to the sink's temperature sensor.

Again, this conversation needs to be with the engineer. It could be an
improvement, and it could dangerous. Elecraft please weigh in.

73, Guy.

On Mon, Jun 18, 2012 at 2:46 PM, Fred Townsend <[hidden email]>wrote:

> Guy: Without putting too fine an edge on it and if I understand David it
> seems he has increased the thermal conductivity and thereby decreased the
> temperature differential across the heatsink assembly. This reduces thermal
> stress and is a good thing and similar to what you strive to do with your
> monster fan. The difference is one of finesse and brute force. Because
> neither surface area nor air path is affected it is unlikely dissipation is
> changed. He is just making better use of the heatsink.
> Thermal conductivity, the reciprocal of thermal resistance, has changed.
> This resistance is part of a thermal time constant affecting how fast the
> fan turns on and off so we should not be surprised the fan turns on and off
> at a different rate.
> 73,
> Fred AE6QL
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Guy Olinger K2AV
> Sent: Monday, June 18, 2012 10:52 AM
> To: David Robertson
> Cc: [hidden email]
> Subject: Re: [Elecraft] KPA 500
>
> My question is whether you actually increased the no-fan heat dissipation
> of
> the heat sink complex that significantly, or whether what you did is faking
> out the heat sensor and causing the fan to NOT come on when it actually
> should.
>
> It bothers me also that the increased dissipation is non-symetrical, and
> will cause one side of the heat sink to be at a different temperature than
> the other. This is a bad situation that theoretically can damage
> transistors by putting unequal mechanical stress on the mounting in high
> heat situations. It also could cause one transistor to be a lot hotter
> than the other. Or it COULD be that what you did equalized heat
> distribution. The problem is that YOU DON'T KNOW WHICH ONE.
>
> Fan speed, when it comes on, size of heat sink, etc and the transistors
> used
> are a very carefully engineered COMBO. I really would not screw around
> with
> it UNTIL you have discussed it with the Elecraft engineer and have his
> concurrence. There is a lot more here than meets the eye. Be very careful
> what you recommend to other owners. Elecraft please weigh in before this
> gets around as an ill-advised urban myth, if indeed it is ill-advised.
>
> Beyond that, why is everyone so aroused by fan speed? Fans keep things
> cool. Fans are good.
>
> My roaring 100 CFM monster fan on my contest 3-1000Z amp, my
> "Loudenboomer,"
> keeps me from melting it when I qsy all over the band and don't remember to
> retune it. I get pretty stupid late into a contest.
> Roaring fan makes 3-1000Z last long time. 3-1000Z getting expensive and
> hard to find. Roaring fan is my friend. Need to use headset anyway for
> best diversity on 160. Use noise cancelling headset, can't hear the roar.
>
> Fans are your friend.
>
> 73, Guy.
>
> On Mon, Jun 18, 2012 at 7:42 AM, David Robertson <[hidden email]>
> wrote:
>
> > Everyone,
> >
> > I have had my KPA500 linear for some time now and have been really
> > happy with it. I use it with my K3 and they communicate with each
> > other via the
> > DB15 AUX cable that I built ( the one furnished by Elecraft was too
> short).
> >
> > The only issue I have encountered is the finals in the linear seem to
> > heat up rather quickly causing the fan to kick in in a rather short
> > period of time. it doesn't matter if I use the dummy load or a good
> > match antenna. I also noticed the finals seem to cool rather quickly
> > after the transmittion is terminated and the fan turns on after about
> > 30 seconds to one minute after starting a ssb transmittion then goes
> > to a higher speed after about
> > 30 seconds more. If my transmittion time is greater then 2 to 3
> > minutes the fans go to high and the final temperature is around 70
> > degrees C. I have never had the linear go in to a fault because of heat.
> >
> > The fix.
> >
> > I removed the top, front, and right side panels of the KPA500. When I
> > first built the linear I realized the mounting screws that mount the Z
> > panel to the amplifier module were too long so I used the shorter ones
> > that would normally go to mount the top panel. On inspecting these
> > screws they were tight. Looking at the right panel I noticed there are
> > 4 screws that mount the panel directly to the amplifier's heat sink.
> > They were not as tight as I would have liked. I wanted to get the most
> > efficient heat transfer from the module so I carefully applied some
> > heat sink compound to the side of the heat sink of the amplifier
> > module before carefully mounting the right sied panel back on the
> > amplifier. I carefully made sure the 4 screws that mount from the
> > panel to the heatsink ( which are normally covered by the
> > handle) were solidly and carefully tightened. After inspecting the
> > transformer connections and the rest of the inside of the linear I
> > reassembled it and tested it out.
> >
> > Findings.
> >
> > Now when I am running ssb typically the fan doesn't come on until well
> > in to the qso and never has the fan reach high mode. If I brick the
> > key at 500 watts into a dummy load the fan goes high after about 2
> > minutes. I also noted the finals heat up slower and cool slower and
> > the left panel temperature follows the final temperature..
> >
> > Now the amp seems very happy and I am not bugged by the constant fan
> > noise during a qso.
> >
> > I thought I would pass this on to everyone.
> >
> > Thanks and 73
> > Dave KD1NA
> > ______________________________________________________________
> > 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
>
>

k6dgw

Re: KPA 500

In reply to this post by Dave KD1NA

Hmmm ... Tight screws yes. Beyond that, I'd be somewhat wary of
re-engineering the thermodynamics of the KPA500 ... OK, very wary. I
have a KX1, K2, K3, P3, and KPA500. They all have one thing in common:
Elecraft equipment is very carefully and meticulously engineered --
electrically, mechanically, and thermodynamically. My 500 on RTTY at
500W stabilizes at about 69 C. The fan seems to come on high [the only
speed I can hear with the cans on] at 70 C, and it does occasionally but
the temp drops immediately and it cycles down. I'd check with Elecraft
Engineering before changing anything.

73,

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

On 6/18/2012 4:42 AM, David Robertson wrote:

> The fix.
>
> I removed the top, front, and right side panels of the KPA500. When I first
> built the linear I realized the mounting screws that mount the Z panel to
> the amplifier module were too long so I used the shorter ones that would
> normally go to mount the top panel. On inspecting these screws they were
> tight. Looking at the right panel I noticed there are 4 screws that mount
> the panel directly to the amplifier's heat sink. They were not as tight as
> I would have liked. I wanted to get the most efficient heat transfer from
> the module so I carefully applied some heat sink compound to the side of
> the heat sink of the amplifier module before carefully mounting the right
> sied panel back on the amplifier. I carefully made sure the 4 screws that
> mount from the panel to the heatsink ( which are normally covered by the
> handle) were solidly and carefully tightened. After inspecting the
> transformer connections and the rest of the inside of the linear I
> reassembled it and tested it out.

Guy, K2AV

Re: KPA 500

In reply to this post by Guy, K2AV

On Mon, Jun 18, 2012 at 2:59 PM, Guy Olinger K2AV <[hidden email]>wrote:

>
> Again, this conversation needs to be with the engineer. It could be an
> improvement, and it could dangerous. Elecraft please weigh in.
>

Hi again, David,

I have the following from Robert Friess, who is Elecraft's designer on this
product:

--------

Hi Guy,

Reducing the thermal resistance to the side panel will have a negligible
effect on cooling the amplifier. There are several reasons for this. Most
important is that the side panel is made of steel which has a much higher
thermal resistance than aluminium. Next, the internal heat sink has forced
air cooling and a much larger surface area which provides much better heat
exchange than convection over the side panel. Finally, the side panel is
some distance from the output devices resulting in a considerable thermal
gradient between the transistors and the side panel.

The temperature sensor is about 1 inch from the output devices on the
aluminum heatsink and tracks the case temperature of the transistors very
well.

I can't offer any explanation for the observed result when the thermal
compound was added. It shouldn't make any difference at all.

73,
Bob, N6CM

-------

Perhaps your reassembly of various items fixed a current path somewhere,
something mechanical? Your results did seem strange to me from the onset.

Glad yours is working correctly now.

73, Guy.
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rodolfo

Re: KPA 500 Fan Noise and cooling performance

In reply to this post by Donehrlich@q.com

I put a big fan (140x140mm) on top louvers for cooling, air injected into
it, and temperature drops, sin is not available a quiet fan (like computers)
... maybe in the future ...
rodolfo IK4VFD
----- Original Message -----
From: <[hidden email]>
To: <[hidden email]>
Sent: Monday, June 18, 2012 8:11 PM
Subject: [Elecraft] KPA 500 Fan Noise and cooling performance

>
> On 6/18/2012 4:42 AM, David Robertson wrote: ( ... a long message I
> won't include here where he improved amplifier cooling by tightening
> heatsink/right panel screws and used heatsink compound.)
>
>
> I operate my KPA500 with the fan speed set to #1 continuously which
> delays the increase in the increase in fan speed once the amplifier
> starts putting out power. My amplifier did not exceed 58 deg C after 10
> minutes at 500 watts carrier output into a dummy load and it stabilized
> at about 60 degrees in a 25 degree C room. My right panel to heatsink
> screws (the ones under the handle) were all tight and that explains why
> my experience was better than was Dave's originally before he tightened
> his heatsink screws and added heatsink compound. I then added heatsink
> compound to the mating surface between my heatsink and the right side
> panel. There was no difference in cooling performance at all. I just
> wanted to know .. and now I do .. and so do you.
>
> The KPA500 fan is as quiet as any muffin fan ought to be but it was
> still annoying to me. That is not an amplifier fault .. it is just that
> I have good hearing and I prefer a *very quiet shack. For those who may
> be like me in that regard here is how I reduced the normal fan noise of
> my amplifier. In my amplifier much of the fan noise was actually coming
> from the sheet metal of the amplifier structure which was being excited
> by the vibration of the fan which is rigidly attached to the amplifier
> structure so that fan vibration was communicated to the structure which
> then resonated and amplified the fan noise. When I removed the fan and
> held it loosely in my hand while it was running I could feel the light
> high frequency 'buzz' produced by the rotating magnetic field of the fan
> and also, crucially, the lower frequency throb caused by a slight weight
> imbalance in the rotor. I used a small piece of sticky pad (normally
> used to mount components to a chassis, etc) and placed this very small
> weight at various points on the rotor blades until, by trial and error,
> found the 'sweet' spot which resulted in greatly reduced throb. That
> reduced fan noise considerably.
>
> Then, to reduce transmission of fan vibration to the amplifier structure
> even further, I mounted the fan loosely to the back of the amplifier
> using soft quarter-inch cushions between the fan and the amplifier. I
> used light wire to do the actual attachment instead of the long screws
> that are standard. The overall effect is considerably less fan noise
> and I am very happy about that. The fan mounting is fragile and not to
> be recommended if the amplifier is to be moved very much but in my
> installation it is just fine. By the way, I carefully compared cooling
> performance before and after the fan mounting modification and found no
> difference at all. I also noticed during my testing that the direction
> of airflow makes no difference.
>
> Don K7FJ
>
>
>
>
>
>
> ______________________________________________________________
> 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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Controllato da AVG - www.avg.com
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06/19/12 08:49:00

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Guy, K2AV

Re: KPA 500 Fan Noise and cooling performance

Computers quiet? Obviously have not heard mine. I have tried to get
after-market fans that were advertised as "quiet", but no luck. Even some
that others swore were much quieter. Apparently that which actually makes
a fan quiet is not part of quality control. I've seen two fans of the same
model number that simply don't look the same. Go figure.

I've given up. Until I can go into a store and somehow listen to the exact
one I'm buying, I don't believe any of the advertising.

73, Guy.

On Tue, Jun 19, 2012 at 1:39 PM, rodolfo <[hidden email]> wrote:

> I put a big fan (140x140mm) on top louvers for cooling, air injected into
> it, and temperature drops, sin is not available a quiet fan (like
> computers)
> ... maybe in the future ...
> rodolfo IK4VFD
> ----- Original Message -----
> From: <[hidden email]>
> To: <[hidden email]>
> Sent: Monday, June 18, 2012 8:11 PM
> Subject: [Elecraft] KPA 500 Fan Noise and cooling performance
>
>
> >
> > On 6/18/2012 4:42 AM, David Robertson wrote: ( ... a long message I
> > won't include here where he improved amplifier cooling by tightening
> > heatsink/right panel screws and used heatsink compound.)
> >
> >
> > I operate my KPA500 with the fan speed set to #1 continuously which
> > delays the increase in the increase in fan speed once the amplifier
> > starts putting out power. My amplifier did not exceed 58 deg C after 10
> > minutes at 500 watts carrier output into a dummy load and it stabilized
> > at about 60 degrees in a 25 degree C room. My right panel to heatsink
> > screws (the ones under the handle) were all tight and that explains why
> > my experience was better than was Dave's originally before he tightened
> > his heatsink screws and added heatsink compound. I then added heatsink
> > compound to the mating surface between my heatsink and the right side
> > panel. There was no difference in cooling performance at all. I just
> > wanted to know .. and now I do .. and so do you.
> >
> > The KPA500 fan is as quiet as any muffin fan ought to be but it was
> > still annoying to me. That is not an amplifier fault .. it is just that
> > I have good hearing and I prefer a *very quiet shack. For those who may
> > be like me in that regard here is how I reduced the normal fan noise of
> > my amplifier. In my amplifier much of the fan noise was actually coming
> > from the sheet metal of the amplifier structure which was being excited
> > by the vibration of the fan which is rigidly attached to the amplifier
> > structure so that fan vibration was communicated to the structure which
> > then resonated and amplified the fan noise. When I removed the fan and
> > held it loosely in my hand while it was running I could feel the light
> > high frequency 'buzz' produced by the rotating magnetic field of the fan
> > and also, crucially, the lower frequency throb caused by a slight weight
> > imbalance in the rotor. I used a small piece of sticky pad (normally
> > used to mount components to a chassis, etc) and placed this very small
> > weight at various points on the rotor blades until, by trial and error,
> > found the 'sweet' spot which resulted in greatly reduced throb. That
> > reduced fan noise considerably.
> >
> > Then, to reduce transmission of fan vibration to the amplifier structure
> > even further, I mounted the fan loosely to the back of the amplifier
> > using soft quarter-inch cushions between the fan and the amplifier. I
> > used light wire to do the actual attachment instead of the long screws
> > that are standard. The overall effect is considerably less fan noise
> > and I am very happy about that. The fan mounting is fragile and not to
> > be recommended if the amplifier is to be moved very much but in my
> > installation it is just fine. By the way, I carefully compared cooling
> > performance before and after the fan mounting modification and found no
> > difference at all. I also noticed during my testing that the direction
> > of airflow makes no difference.
> >
> > Don K7FJ
> >
> >
> >
> >
> >
> >
> > ______________________________________________________________
> > 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
>
>
>
> --------------------------------------------------------------------------------
>
>
>
> Nessun virus nel messaggio in arrivo.
> Controllato da AVG - www.avg.com
> Versione: 9.0.930 / Database dei virus: 2433.1.1/5079 - Data di rilascio:
> 06/19/12 08:49:00
>
> ______________________________________________________________
> 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
>

Tony Estep

Re: KPA 500 Fan Noise and cooling performance

On Tue, Jun 19, 2012 at 1:26 PM, Guy Olinger K2AV <[hidden email]>wrote:

> ...I have tried to get after-market fans that were advertised as "quiet",
> but no luck...

=======
Agreed. I recently built a tower computer and put in a neat-looking 18 cm.
fan in the top of the case. Because it is so huge and runs at low RPM, it
is a little quieter than my previous computer, and it does have the
advantage of emitting an eerie red glow from its LED-illuminated clear
plastic blades. However, it is just another failed experiment in my attempt
to find a quiet fan.

I read somewhere that Apple has a neat fan design in its newest machines.
It is balanced but the blades are various different sizes, which apparently
creates a spectrum of audio resonances instead of a single hum. However,
I've never heard one in real life so I can't attest that it works.

Tony KT0NY

--
http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352
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KC6CNN

Re: KPA 500 Fan Noise and cooling performance

CONTENTS DELETED

The author has deleted this message.

Scott Manthe-2

Re: KPA 500 Fan Noise and cooling performance

My solution was to buy a Mac Mini, which is as quiet as a church mouse.

73,
Scott, N9AA

On 6/19/12 2:43 PM, Gerald Manthey wrote:
> Solution - the Dyson blade less fan. Hihi
>

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Wayne Conrad

Re: KPA 500 Fan Noise and cooling performance

In reply to this post by KC6CNN

I could be wrong, but I think that the Dyson "bladeless" fan has, in its
base, a regular ol' fan, with blades. As I understand it, that fan
blows air out of holes in the trailing edge of the circular airfoil.
Aerodynamic effects cause a larger volume of air to be dragged through
the airfoil than the fan itself is pushing through the little holes.

If that's so, it ought to be no worse a generator of RFI than any other fan.

73, Wayne Conrad KF7QGA

On 06/19/12 12:24, Ron D'Eau Claire wrote:

> Has anyone every operated one of those in close proximity to an HF rig?
>
> We built such fans in College waaaaay back in the 1950's and they were a bad
> of an RFI generator as any Tesla coil or Van De Graaf generator in the lab!
>
> After all, they work by electrostatic discharge.
>
> Ron AC7AC
>
> -----Original Message-----
>
> Solution - the Dyson blade less fan. Hihi On Jun 19, 2012 1:41 PM, "Tony
> Estep"<[hidden email]> wrote:
>
>
> ______________________________________________________________
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>

Jim Brown-10

Re: KPA 500 Fan Noise and cooling performance

In reply to this post by Guy, K2AV

On 6/19/2012 11:26 AM, Guy Olinger K2AV wrote:
> Computers quiet? Obviously have not heard mine. I have tried to get
> after-market fans that were advertised as "quiet", but no luck.

For a long time, I've been buying only top line Thinkpads (laptops), and
they're pretty quiet. Back when I was buying tower computers for my
office, I replaced the power supplies with Silencer models made by PC
Power and Cooling. They're also very well built supplies.

pcpower.com

73, Jim K9YC
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ve3dvy

Re: KPA 500 Fan Noise and cooling performance

In reply to this post by KC6CNN

It would be interesting and perhaps not good in the shack if this were
the case but these are not electrostatic.

they are nothing more than a fancy venturi to amplify air flow Air
enters the base of the unit through a “mixed flow impeller” a fancy name
for a turbo like fan. and is forced out of a slot. The slot runs around
the inside of the ring-shaped fan body, across a “aircraft wing shape”
and then outward into the room. In short, it sucks air in through the
base and blows it out of a very thin slot in the inside of the
ring-shaped upper body drawing additional air though it.

On 6/19/2012 3:24 PM, Ron D'Eau Claire wrote:

Eric Swartz - WA6HHQ

Re: KPA 500 Fan Noise and cooling performance

Administrator

In reply to this post by Guy, K2AV

Folks, this thread is drifting too far afield. Let's end the general fan discussion at this time.

In the future, please resist the urge to post on OT threads like this when there are already a lot of responses in a short period, like this one.

While OT threads are allowed, we ask that people resist the urge to prolong them, in the interest of improving the list signal to noise level.

73,
Eric
Elecraft List Manager and moderator
www.elecraft.com
_..._

On Jun 19, 2012, at 9:46 PM, "Ron D'Eau Claire" <[hidden email]> wrote:

> ABSOLUTELY! My HP mini-tower has what is called a whisper quiet fan and it
> is very quiet. It certainly does not interfere with conversation, even when
> carried on across our open office between desks ten feet apart.
>
>
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