[Elecraft] Elecraft] KXPA100 Thermal Fault

[Edward R Cole]

Re: blowing air vs drawing air, the object is to increase air flow 
over the heat sink (or tube if no heat sink).  If one does not have a 
plenum directing air over the entire heat sink surface, my bet is 
with blowing.  Drawing air is effective if there is a plenum 
confining the air flow over the heat sink surface.

I you are cooling a tube with fins like some of the 3CX or 4CX types 
then you need the extra force of a blower due to the high air 
resistance (back pressure) thru the fins.  Example a 8877 
(3CX1500A).  I have both a blower and 7-inch radial exhaust fan on 
that amp.  Exhaust fan lowers back pressure that the blower works into.

All my other amps are currently configured with fans that blow down 
onto the heat sink.  I will be installing five fans on a 6m Harris TV 
amplifier (1100w with 16 transistors) that draws air.  That is needed 
as air is drawn thru several holes from the input side of the amp for 
cooling the input components by pulling air into the output side.

73, Ed - KL7UW
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