[Elecraft] KPA1500 - adding fans

Fri Aug 10 14:32:40 EDT 2018

The kind of noise the amp makes is related to but a separate issue to 
the loudness.  Last night I was doing some comparison listening while 
trying to find some DX on 20m and noticed that while the FAN2 setting 
was definitely louder than FAN1, it seems a more "pleasant" noise 
compared to FAN1 which tends to have some sort of a sequel-type note to 
the sound it makes.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 10-Aug-18 1:26 PM, Jim Brown wrote:
> This is an excellent post, and I agree with all of it.
>
> I will add that acoustic considerations also STRONGLY affect the noise 
> produced in any ventilation system, and it is science more than an 
> art. The engineers who specialize in this field are called acoustic 
> consultants, their formal training is in physics and mechanical 
> engineering, and the acoustics specialization begins at the Masters 
> Degree level. In my professional life (I'm long retired) I worked with 
> professionals in this discipline in the design of sound systems and 
> acoustics for large public spaces, where one of their concerns was 
> making very good HVAC systems so quiet that they could not be heard in 
> concert halls. The considerations there are same as in the KPA1500 -- 
> the turbulence (or lack thereof) of air flow, the path, air speed, the 
> fans themselves, vibration isolation.
>
> I do NOT recommend that users experiment with ventilation. I DO 
> strongly urge Elecraft to retain the services of a good acoustic 
> consultant to address complaints I've seen about fan noise.
>
> 73, Jim K9YC
>
>
>
> On 8/10/2018 10:52 AM, K8ZCT wrote:
>> My KPA1500 is S/N 00059. I don't operate full power all the time. I 
>> live in a
>> compromised antenna
>> area, and so I will use the amp as required to make contacts that are
>> difficult assuming I can hear the station well enough to have the QSO.
>>
>> I have not had problems with the weird display issue that has been 
>> reported,
>> and also someone recently replaced their antenna tuner to solve a 
>> problem
>> which I have not seen either yet. Thanks for this site, as it gives us a
>> heads up if we would have similar issues with our equipment.
>>
>> Maybe I don't run the amp hard enough, my antenna will take 1500 
>> watts, but
>> I probably never push it that hard for long periods. I run FT8, but 
>> with 100
>> watts or less and I have made plenty of contacts. FT8 is whole another
>> discussion. SSB is the least difficult for the amp to deal with. CW is
>> harder and RTTY, FM,FT8 and AM are the worst.
>>
>> The fans on the power supply make some noise, but I have had several 
>> tube
>> amps over the last 40 years that are louder. I haven't installed the 
>> latest
>> software update issued in July, so I need to see if that makes any
>> difference.
>>
>> I was involved with the design specification, and purchase of medium and
>> high voltage transformers for my career. Cooling of electrical 
>> equipment is
>> a little more complex than just installing fans. There are proper air 
>> flow
>> requirements to look at in the design, so the air doesn't get short
>> circuited, and actually hurt the process. So more air isn't always 
>> better if
>> it is not properly applied.
>>
>> Transformers have RTD's or Thermocouples imbedded in the windings to 
>> measure
>> transformer temperature, because that is the "hottest spot" of any
>> transformer. The hot spot temperature is made up of the ambient air
>> temperature normally 40 C maximum is used with a 30C average over a 
>> 24 hour
>> period, and the temperature rise of the unit under load. Most electrical
>> equipment design is based on a 40C maximum ambient but I didn't see 
>> in the
>> manual what Elecraft considered for a maximum. Regardless, the 
>> ambient heat
>> around the amplifier must be controlled and not trapped around the unit.
>> An air conditioned space or proper ventilating for area is critical. 
>> If you
>> don't remove the heat your unit will work harder and could make more 
>> noise
>> than other units.
>>
>> Wayne or Eric can comment, but RF amplifiers must follow similar laws of
>> physics. The heat sink temperature must be maintained or the devices
>> primarily the LDMOS final amp units will fail. There are average and
>> maximums I would assume are used in the Elecraft design. Ambient air 
>> must be
>> kept at a certain maximum and air flows must not be restricted.
>>
>> At this time, it good to provide feedback to the vendor on operational
>> concerns of the equipment, and I did plenty of that over the years. 
>> However,
>> I usually realized there were some people, who did this for a living, 
>> and I
>> was a consumer maybe a smart consumer, but still I didn't design
>> transformers as my main employment.
>>
>> With all the KPA1500's still under warranty I don't think it is a 
>> good idea
>> to modify or change anything with regards to the operation, and 
>> design of
>> the KPA1500. Again, I am not Wayne or Eric, but I think you are doing 
>> it at
>> your risk.
>>
>> I will wait for Wayne and Eric to come out with improvements, and 
>> updates
>> based on customer and other inputs, but I will not modify the KPA1500 in
>> anyway including external programs that change the operation without the
>> supplier approval. I guess after the warranty period anyone can do 
>> what they
>> want, but don't expect the supplier to honor any warranty issues that 
>> may
>> have been created due to prior modifications of operation.
>>
>> Just as with a transformer, cooling of an RF amplifier is critical to 
>> the
>> proper operation and long term reliability and life of the unit. Heat 
>> is the
>> main cause of failure of any electrical equipment!
>>
>>
>> Bill, K8ZCT
>>
>>
>>
>>
>>
>>
>> -- 
>> Sent from: http://elecraft.365791.n2.nabble.com/
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>
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