[Elecraft] KPA500 Fan Question

[Mike Maloney]

 Your resting temperature at 42C seems TOO warm to me?   My KPA resting temp runs about the same as ambient temperature of shack, 25-30C.   With 25-30W drive from TS-890,my KPA seldom reaches 3rd stage 60 degrees.   Have you checked SWR or cable between 890 and KPA?  
73, Mike AC5P
    On Sunday, May 14, 2023 at 12:38:56 PM CDT, James Bennett via Elecraft <elecraft at mailman.qth.net> wrote:  
 
 Yes, but the amp is not seeing the mis-match, correct? The tuner is taking care of that mis-match and I would have thought that the amp should be perfectly happy… Yes?

> On May 14, 2023, at 11:35 AM, Dr. William J. Schmidt <bill at wjschmidt.com> wrote:
> 
> You are trying to transform a mis-match and that burns energy.  That’s why the fan is running.
> 
> 
> 
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of James Bennett via Elecraft
> Sent: Sunday, May 14, 2023 12:24 PM
> To: Elecraft Reflector Reflector <elecraft at mailman.qth.net>
> Subject: [Elecraft] KPA500 Fan Question
> 
> Got a question (problem?) regarding the fan in my KPA500. I'm driving the amp at 29 watts from a Kenwood TS-890S. The amp is connected to a KAT500, which in turn is hooked to a 30 foot tall Zerofive flagpole vertical. The tuner has provided me with a nice 1.2:1 SWR, as displayed on the amp. The resting temp of the amp shows 42C. At 29 watts input to the amp, I’m seeing about 480 watts of power from the amp. The amp has nothing sitting on top of it, and the wall behind it is over 12” away. There is about 2” clearance on either side of the amp, and it is sitting on top of the KAT500.
> 
> The issue: The fan comes on in a very short time - less than 20 seconds - and the temp display runs up to 50+ degrees. If I start calling CQ or get into a QSO, it doesn’t take long for the temp to show over 60 degrees and the fan is running at max.
> 
> When I had a K3 and more recently, a K4D - this did NOT happen. The fan would come on but NEVER at the max, loud level. Interestingly, many moons ago I also had a KX3 and had it connected to the KPA500. I noticed that the fan would also come on fairly quickly with that rig driving the amp, but I never thought too much about it. Until now...
> 
> But now, I think there is some sort of problem. It seems to me that the temp shouldn’t get that high that fast nor should the fan start roaring in that short amount of time. I could understand it if the SWR was really bad, but at 1.2:1????
> 
> Any ideas why the amp fan should be acting this way with a non-K3 or non-K4 driving it?
> 
> Jim / K7TXA
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