[Elecraft] KPA-1500 Fan Noise - YouTube ?

[WILLIE BABER]

While running stations on 160m at a high rate, the finals of an Omni VI got so hot that output dropped to zero.  Once the finals cooled for maybe about five minutes, full output returned.  We then put a small fan on the heat sink fins and experienced no further problem.  No damage at all to the components.  Unfortunately, the same Omni VI was hit by lightning some years later.

73, Will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

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On Sat, 6/2/18, Gmail - George <gdanner12 at gmail.com> wrote:

 Subject: Re: [Elecraft] KPA-1500 Fan Noise - YouTube ?
 To: elecraft at mailman.qth.net
 Date: Saturday, June 2, 2018, 6:10 AM
 
 One other thought to keep in mind
 - solid state amps need a lower delta T 
 than tube amps. Tubes like to run hot - solid
 state devices not so much.
 
 I've seen a tube with the fins so hot that
 the solder was in globs, while 
 the
 transmitter was still operating. I doubt any solid state
 final would 
 have survived that heat.
 
 When we installed our solid
 state TV transmitter, it was a new learning 
 curve in cooling. Both transmitters were 30 kW
 class AB1. The tube 
 transmitter moved air
 faster through 3 tubes but had almost 3 times the 
 temperature rise than the specs for the solid
 state transmitter. Our HVAC 
 company and
 architect worked on several complex systems with air mixers
 
 until we just decided to use wall mounted
 air conditioners into the room 
 behind the
 transmitter racks and exhausted to the front of the
 transmitters.
 
 Our solid
 state transmitter did meet the OSHA limit for 8 hours
 exposure to 
 noise but just barely. It was
 very noisy compared to the tube unit.
 
 No tube transmitter I have ever used had a
 temperature shut down on any of 
 the tube
 stages.
 
 73 George AI4VZ
 
 
 
 -----Original Message----- 
 From: Don Wilhelm
 
 Only one bit of correction.  If the output
 power is 1500 watts and the
 efficiency is
 50%, that 1500 watts is only half the total power
 consumed, so there is 1500 watts of power that
 must be exhausted as heat.
 
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