[Elecraft] KPA Fan Noise

[Toby Pennington]

Eric,   thanks for the info about the fan speeds.   I am glad to know that 
my amp is working correctly in regards to the different cooling speeds of 
the fan.  I really like having the amp in front of me because I use the band 
buttons on the amp quite a lot to change bands with.

I only have a issue with the fan noise when it get to the last speed and 
then begins to cycle on and off at that speed.  I understand about solid 
state amps needing lots of cooling,  as I used to have a PW 1.  I put that 
amp in the basement on a chest of drawers and used the remote controller in 
my upstairs location because of the constant noise.  That amp had three 
different fans and when the amp was turned on one of the fans cranked up and 
it only got worse from there.

However,   I do wish there was a way to minimize the KPA fan noise when on 
CW or RTTY.

Thanks for your response to my question!    Toby  W4CAK


----- Original Message ----- 
From: "Eric Swartz - WA6HHQ, Elecraft" <eric at elecraft.com>
To: "Toby Pennington" <toby423 at embarqmail.com>
Cc: <Elecraft at mailman.qth.net>
Sent: Thursday, November 08, 2012 8:34 AM
Subject: Re: [Elecraft] KPA Fan Noise


> Hi Toby, I believe the 6th fan speed setting is OFF. :-)  Your temps look 
> about right to me.
>
> The KPA500 is about as quiet as we can make it for a compact solid state 
> 600W amp. We took special care to select the quietest fans we could get 
> for this application. In general our user feedback has been extremely 
> positive with respect to this. I'm a user too and have not had a problem 
> with it, but my operating habits may be different than yours.
>
> Solid state amps must move more air over their cooling fins at a much 
> higher rate than tube amps due to the lower operating temperature 
> difference between transistors vs tubes and the ambient air. The higher 
> operating temperature of tube amps does provide a more efficient flow of 
> energy away from the tube to the much cooler surroundings.
>
> Also, since the KPA500 is pretty much automatic in its operation, it 
> certainly can be located away from the operating position. Providing more 
> clearance for cool air flow above and behind the amp will also help. But 
> in general, contest usage of any compact solid state amp is going to 
> generate a higher level of fan noise.
>
> Regards,
>
>
> Eric
> ---
> www.elecraft.com
>
> On 11/8/2012 5:51 AM, Toby Pennington wrote:
>> Eric,   yesterday Don emailed a number of us off list with the things he 
>> did to quieten the fan noise of the KPA500..
>>
>> I will leave it up to him if he wants to post his modifications or not, 
>> but one of the things he suggested was to entirely isolate the fan itself 
>> from all metal sheeting or chassis or the amp.
>>
>> He does not utilize metal screws to hold the fan in place now,  but uses 
>> other means to hold the fan in place,  thereby eliminating vibrations 
>> from the fan from transferring to any other part of the amp.
>>
>> He also actually balanced the blades of the fan so there was no noise 
>> that occured from imbalance of the fan blades.
>>
>> He did other things but now says his fan speed never gets over a setting 
>> of 1 or 2.
>>
>> AS an aside,   I tried to determine at what temperatures each fan speed 
>> came on at and am missing one speed.  When I first noticed the fan speed 
>> came on it was at 50C;,  then 55C,  60C,  65C, and then 70 C.   That is 
>> only 5 speeds so I am missing one speed.  Can you tell me what 
>> temperature setting I am missing?  My thinking is I may be skipping one 
>> fan speed somehow and that could be making the amp overheat faster.
>>
>> Thanks for your help.    Toby  W4CAK
>>
>>
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