[Elecraft] KPA 500

[Guy Olinger K2AV]

On Mon, Jun 18, 2012 at 2:59 PM, Guy Olinger K2AV <olinger at bellsouth.net>wrote:

>
> Again, this conversation needs to be with the engineer.  It could be an
> improvement, and it could dangerous.  Elecraft please weigh in.
>

Hi again, David,

I have the following from Robert Friess, who is Elecraft's designer on this
product:

--------

Hi Guy,

Reducing the thermal resistance to the side panel will have a negligible
effect on cooling the amplifier.  There are several reasons for this.  Most
important is that the side panel is made of steel which has a much higher
thermal resistance than aluminium.  Next, the internal heat sink has forced
air cooling and a much larger surface area which provides much better heat
exchange than convection over the side panel. Finally, the side panel is
some distance from the output devices resulting in a considerable thermal
gradient between the transistors and the side panel.

The temperature sensor is about 1 inch from the output devices on the
aluminum heatsink and tracks the case temperature of the transistors very
well.

I can't offer any explanation for the observed result when the thermal
compound was added.  It shouldn't make any difference at all.

73,
Bob, N6CM

-------

Perhaps your reassembly of various items fixed a current path somewhere,
something mechanical?   Your results did seem strange to me from the onset.


Glad yours is working correctly now.

73, Guy.