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: <donehrl...@q.com> To: <elecraft@mailman.qth.net> 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:Elecraft@mailman.qth.net > > 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
