[Elecraft] use the fan on the KPA 500

[Ron D'Eau Claire]

Yes, some people complain about "fly specks", but not many, IMX. I treat any
report as legitimate until proven otherwise. A key value of this reflector
has always been to compare notes between users of various Elecraft gear and
to help people who are still learning. 

We've seen several good suggestions about why the level would be different
from place to place already, such as the one about ensuring the table under
the amp isn't acting like a sounding board. 

What caught my attention were the reports that the level of noise changed
while nothing obvious was being done to cause it. Changes in mains voltage
or frequency within normal limits should not do that. 

The real challenge is to define "normal". As we all know, some hum is
present in *any* energized transformer, and it normally increases as the
load current increases. There's no easy way to quantify the levels or
changes in levels people are experiencing, so it deserves some investigation
before deciding whether what people hear is "normal" or not.

You remind me of the vacuum tube amps with the high-pressure air cooling
systems driven by squirrel-cage blowers. Yes, they can be *noisy*! It was
one reason some hams went to the effort to use water-cooled "legal limit"
amps. In the early days I avoided running RTTY at home; I didn't want to
listen to the racket from my surplus Model 15 hammering away (and neither
did my family). Nowadays it is clear that most Hams expect their rigs to be
quiet, especially K3 owners. That's another complicating factor when
evaluating reports. 

I leave the KPA500 fan on normal, which means it is inaudible most of the
time in an extremely quiet shack (not even a computer fan running). I trust
the Elecraft engineers to have created a robust design in the KPA500; they
haven't failed to do so with any product yet. I don't expect to see any
degradation in finals life or system reliability running it as specified. 

73, 

Ron AC7AC


-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of jim danehy
Sent: Wednesday, September 28, 2011 9:56 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] use the fan on the KPA 500

The humming of the transformer in the KPA 500  is somewhat analogous to the
SWR indicator on the KPA500 showing yellow leds. The external antenna has a
lot to do with the SWR. The primary's  ac  voltage and frequency (hz) has
the same type of external affect on the transformer's  humming. To assume
that the frequency (hz) is the same at all locations is wishful thnking.
Elecraft already gave you the remedy for the input voltage.  Too many
appliance operators.

I operate the fan on my KPA 500 at < 2>  all the time. I run 540 watts
output most of the time. I operate RTTY too. I do monitor the temp of the
finals. I see a fair amount of difference when the fan is left in NOR versus
2. Why would you not run the fan ? The aversion to the alleged noise is
difficult to comprehend. What comes out of the speaker on the K3 or the
headphones is always louder than the ambient noise of the amp with the fan
running on 2. I think that the life of the finals is probably significantly
extended with constant use of the fan. I have tube amps that generate 4 or 5
times the fan noise than a KPA 500 with the fan at 2. I also have pretty
acute hearing. Seems like fly specing to me.