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How and How Often to Clean KPA-1500 Cooling Systems?

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N4ZR

How and How Often to Clean KPA-1500 Cooling Systems?

The other day I noticed some buildup of dust on the top vents of my
power supply. I used a vacuum on them and was surprised by how much
appeared to come out from inside. This raised a question - how often is
it recommended to clean the cooling systems of the amp and its power
supply, and what's the best way to do it?

--
73, Pete N4ZR
Check out the new Reverse Beacon Network
web server at <http://beta.reversebeacon.net>.
For spots, please use your favorite
"retail" DX cluster.

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Jim Brown-10

Re: How and How Often to Clean KPA-1500 Cooling Systems?

On 3/27/2021 9:23 AM, N4ZR wrote:
> The other day I noticed some buildup of dust on the top vents of my
> power supply.

Neighbor K6XX is the mfg engineer for both of Elecraft's amps. Bob lost
everything (except one of his towers) in a big wildfire this summer,
along with three other hams I know. For a contest a few months ago, he
borrowed my KPA1500, and when he returned it, told me it was super
dusty. My shack is pretty dusty, and I was running the fans all the
time, often at a high setting, because I use WSJT modes on 6M and 160 a
lot. His advice was to set the fan speed default to zero and let the amp
determine the fan speed. Using 120 sec TX cycles at 1kW on 160, I've
seen 95C temps, and the amp is still happy. I wouldn't do that on 6M,
where the amp is least efficient.

73, Jim K9YC
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N4ZR

Re: How and How Often to Clean KPA-1500 Cooling Systems?

I'm uncomfortable with temp above 70C. I infer from the manual that the
displayed temp is that of the final transistor heat sink, and they say
it will hard fault at 112C. Not in my shack! Still looking for an
answer to the cleaning question, though, particularly for the power supply.

73, Pete N4ZR
Check out the new Reverse Beacon Network
web server at <http://beta.reversebeacon.net>.
For spots, please use your favorite
"retail" DX cluster.

On 3/27/2021 2:44 PM, Jim Brown wrote:

> On 3/27/2021 9:23 AM, N4ZR wrote:
>> The other day I noticed some buildup of dust on the top vents of my
>> power supply.
>
> Neighbor K6XX is the mfg engineer for both of Elecraft's amps. Bob
> lost everything (except one of his towers) in a big wildfire this
> summer, along with three other hams I know. For a contest a few months
> ago, he borrowed my KPA1500, and when he returned it, told me it was
> super dusty. My shack is pretty dusty, and I was running the fans all
> the time, often at a high setting, because I use WSJT modes on 6M and
> 160 a lot. His advice was to set the fan speed default to zero and let
> the amp determine the fan speed. Using 120 sec TX cycles at 1kW on
> 160, I've seen 95C temps, and the amp is still happy. I wouldn't do
> that on 6M, where the amp is least efficient.
>
> 73, Jim K9YC
> ______________________________________________________________
> 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]

k6mrmagnet

Re: How and How Often to Clean KPA-1500 Cooling Systems?

As you know, I run my amp in a single amp, SO2R configuration. During a heavy 2BSIQ session on RTTY, temps reach 90 deg C. Fans go to 5 occasionally. Not a problem. Don’t worry.

My power supply does get quite the dust bunny on top. I just hit it with the vacuum every week when doing the shack. I haven’t noticed the same problem with the RF deck. Perhaps with the fans on super high speed it blows itself out. I’ve had the power supply case off twice, and didn’t see a build up internally. So I’m pretty sure it’s not an issue if you vacuum it regularly.

I have the amp and power supply in a bookshelf type cabinet in the closet. One thing I did when I first set it up was to make a seal around the back of the RF desk. It is a piece of cardboard, stapled to the back edge of the bookshelf, and cut to just fit around the rear of the amp. This keeps the amp from sucking in hot exhaust from the top vents back into the amp. Of course this won’t be a problem if you have the amp on a desk with nothing above it. I have the minimum recommended clearance of 2” above the amp, and 4” above the power supply.

Ken K6MR

From: N4ZR<mailto:[hidden email]>
Sent: Saturday, March 27, 2021 13:09
To: [hidden email]<mailto:[hidden email]>
Subject: Re: [Elecraft] How and How Often to Clean KPA-1500 Cooling Systems?

I'm uncomfortable with temp above 70C. I infer from the manual that the
displayed temp is that of the final transistor heat sink, and they say
it will hard fault at 112C. Not in my shack! Still looking for an
answer to the cleaning question, though, particularly for the power supply.

73, Pete N4ZR
Check out the new Reverse Beacon Network
web server at <http://beta.reversebeacon.net>.
For spots, please use your favorite
"retail" DX cluster.

On 3/27/2021 2:44 PM, Jim Brown wrote:

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w0mu

Re: How and How Often to Clean KPA-1500 Cooling Systems?

I would encourage people to get the gear off the floor. My computers
that were on the floor got far more dirty than when I had them setting
up higher. YMMV

W0MU

On 3/27/2021 4:22 PM, Ken K6MR wrote:

> As you know, I run my amp in a single amp, SO2R configuration. During a heavy 2BSIQ session on RTTY, temps reach 90 deg C. Fans go to 5 occasionally. Not a problem. Don’t worry.
>
> My power supply does get quite the dust bunny on top. I just hit it with the vacuum every week when doing the shack. I haven’t noticed the same problem with the RF deck. Perhaps with the fans on super high speed it blows itself out. I’ve had the power supply case off twice, and didn’t see a build up internally. So I’m pretty sure it’s not an issue if you vacuum it regularly.
>
> I have the amp and power supply in a bookshelf type cabinet in the closet. One thing I did when I first set it up was to make a seal around the back of the RF desk. It is a piece of cardboard, stapled to the back edge of the bookshelf, and cut to just fit around the rear of the amp. This keeps the amp from sucking in hot exhaust from the top vents back into the amp. Of course this won’t be a problem if you have the amp on a desk with nothing above it. I have the minimum recommended clearance of 2” above the amp, and 4” above the power supply.
>
> Ken K6MR
>
> From: N4ZR<mailto:[hidden email]>
> Sent: Saturday, March 27, 2021 13:09
> To: [hidden email]<mailto:[hidden email]>
> Subject: Re: [Elecraft] How and How Often to Clean KPA-1500 Cooling Systems?
>
> I'm uncomfortable with temp above 70C. I infer from the manual that the
> displayed temp is that of the final transistor heat sink, and they say
> it will hard fault at 112C. Not in my shack! Still looking for an
> answer to the cleaning question, though, particularly for the power supply.
>
> 73, Pete N4ZR
> Check out the new Reverse Beacon Network
> web server at <http://beta.reversebeacon.net>.
> For spots, please use your favorite
> "retail" DX cluster.
>
> On 3/27/2021 2:44 PM, Jim Brown wrote:
>> On 3/27/2021 9:23 AM, N4ZR wrote:
>>> The other day I noticed some buildup of dust on the top vents of my
>>> power supply.
>> Neighbor K6XX is the mfg engineer for both of Elecraft's amps. Bob
>> lost everything (except one of his towers) in a big wildfire this
>> summer, along with three other hams I know. For a contest a few months
>> ago, he borrowed my KPA1500, and when he returned it, told me it was
>> super dusty. My shack is pretty dusty, and I was running the fans all
>> the time, often at a high setting, because I use WSJT modes on 6M and
>> 160 a lot. His advice was to set the fan speed default to zero and let
>> the amp determine the fan speed. Using 120 sec TX cycles at 1kW on
>> 160, I've seen 95C temps, and the amp is still happy. I wouldn't do
>> that on 6M, where the amp is least efficient.
>>
>> 73, Jim K9YC
>> ______________________________________________________________
>> 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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>
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>
> ______________________________________________________________
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Elecraft mailing list

Re: How and How Often to Clean KPA-1500 Cooling Systems?

In reply to this post by N4ZR

Re:-

------------------------------------------------------------------------
> Subject: Re: [Elecraft] How and How Often to Clean KPA-1500 Cooling
> Systems?
> Message-ID:
> <[hidden email]>
>
> Content-Type: text/plain; charset="Windows-1252"
>
> As you know, I run my amp in a single amp, SO2R configuration. During a heavy 2BSIQ session on RTTY, temps reach 90 deg C. Fans go to 5 occasionally. Not a problem. Don?t worry.
------------------------------------------------------------------------

90'C is too hot for the heatsink.

One wonders what the actual device junction temperatures (the critical
value) might be for that, but that can't be measured directly. You need
knowledge of the actual power being dissipated, and the various thermal
resistances between junction and heat sink, where you can measure
temperature.

Plus the difference between what the heatsink sensor records, vs the
temperature at the device, varies as well.

Solid-state power devices (DC and RF) do not like heat, the hotter they
are, the less likely they are to last a long and trouble free life.
Plus, all the thermal cycling (heat/cool) can stress soldered joints to
them that will eventually fracture and cause a fault.

Yes, keeping a stable (even hot) temperature will reduce thermal cycling
stress, but the overall MTBF of the devices will still be very much
shorter at elevated temperatures than if they were kept cooler.

Plus, RF device production life-cycles are notoriously short as the
development pace is fast, especially with LDMOS devices. Also, often
the new "better" devices, are different enough to /not/ be drop in
replacements. Electrically or physically.

As for cleaning. As often as needed, every site/shack is different. If
you see dust accumulating on the outside, it's inside too!

Many commercial amps have air inlet filters. But they need to be kept
clean, as a clogged filter is just as bad for cooling, as an inadequate
heatsink/fan combination and no filters.

Regards.

Dave G8KBV

--
Created on and sent from a Unix like PC running and using free and open source software:

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