[Elecraft] KPA-500 fan noise

[AG0N-3055]

On Mon, 2 Jun 2014 06:05:22 -0700 (PDT), Harry Yingst via Elecraft
wrote:

> You could always try replacing the fan with a quieter fan.

I would consider that myself, but only with one recommended by the good
people at Elecraft.  The fan in the KPA is VERY loud when it hits the
last two speeds.  Warp and Turbo Warp would wake my wife in the next
room if she was a light sleeper, although I virtually never get it up
that warm.  It was just my short excursion on 6M FM that really got it
up there fast.  My issue isn't with the fan operation, although I wish
it would come on just a bit earlier than it does.  My issue is with the
sound level out of this particular fan.  It's a screaming banshee when
it gets up there at speed.  It's a very "raw" sound, not the sound of
air moving, but of a high speed motor.

My only hesitation with putting a different fan in it would be
compatibility with the speed control circuitry.  I just won't do it,
especially under warranty, without Elecraft's recommendation and
blessing.  They've got a good product and I want to keep it that way.

Typing this up raised my curiosity and I went to the shack and ran a
control test into my Bird load.  I set my rig at 10W on 52.525 FM, which
gives me 200W output.  With manual fan control, I made sure the amp was
cooled to 33C as a starting point, and then set the fan back to NORmal
setting.  I keyed the rig on FM at the (unmeasured) 10W setting, and sat
back to see what it did.  It took 75 seconds to reach 70C.  At which
point, the fan is at 5, a rather noisy speed.  It seemed to level out at
77-78C for a bit and then went to 80C at 4:50 minutes.  I ended the test
at that point.  At 80, the fan went to 6, the highest speed, screaming
away.  With this test, I'm confident that it would probably handle
anything I would ever do to it in normal operation, especially given the
fact that I'm not dumb enough to do that test at 500W output.  :o)  I
think the fan does a pretty good job, but do wish it was quieter.  I
never hit those higher speeds, except in test conditions like this.  My
normal use has it hitting 70C only on the rarest of occasions.

Gary
-- 
http://ag0n.net
3055: http://ag0n.net/irlp/3055
NodeOp Help Page: http://ag0n.net/irlp