[Elecraft] OT: The Great KPA Fan Mystery

[Edward R Cole]

My comment NOT about Elecraft cooling design, but:

I am finding a lot of amplifier designs place fans to exhaust heated 
air with cool air being drawn into the heat sink by the partial 
vacuum created by the fans.

My 6m converted Harris ch.2 TV linear is set up this way (amp has 
openings in the chassis to circuits on input side as well as the 
final transistors).

My W6PQL 1296 LDMOS 600w amp is cooled in the same fashion.

Only departure is my W6PQL 2m-1500w linear that has four 2-inch 
square fans blowing cool air into the heat sink.  But I augmented air 
flow by adding a 4-inch exhaust fan on enclosure top cover.  The 
intake fans were separated from the heat sink by a 2-inch gap which 
bothered me,so added sheet metal fairings to channel air to the heat 
sink.  Seems to work as heat sink temp remains topped out at 39c 
running 1400w with JT65 (Overtemp trips off 50v supply at 55c).

Even my old 2m-8877 with blower had a 7-inch radial exhaust fan to 
reduce back pressure on the blower.

73, Ed - KL7UW
   http://www.kl7uw.com
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