[Elecraft] KLPA3A power transistor thermal stress concerns

[Nick - VE3EY]

Hi Don

Good question.   I happen to have a Infrared Thermometer.    After bashing
at it for about 20 minutes, the temperature in the vicinity of two
transistors (as measured against the bottom cover) peaked at 50 degrees
Celsius (122 F) but it did not go beyond that.  I ran the rig at 10 watts
on 10 meters which is where most of the drive power is needed.

I suppose that should be OK than.

73 and thanks for your feedback,
Nick
VE3EY

On Tue, Oct 24, 2017 at 9:23 AM, Don Wilhelm <donwilh at embarqmail.com> wrote:

> Nick,
>
> It all depends on your perception of "fairly hot".
>
> My 'rule of thumb' is that if you can hold your fingers on the surface,
> then it is not too hot.
>
> 73,
> Don W3FPR
>
>
>
> On 10/24/2017 7:27 AM, Nick - VE3EY wrote:
>
>> I have a K3s/10 (12 watt version) which I intend to use in the upcoming cq
>> ww cw contest.  This unit does not have KPA3A power brick and cooling fans
>> installed.
>>
>> While doing some trial runs I noticed that the area around the KLPA3A
>> power
>> transistors is getting fairly hot after prolonged contest use.  My guess
>> is
>> the transistors are working harder when used as finals.  The rig needs to
>> produce between 6 and 12 watts to properly drive the SS amp I intend to
>> use.
>>
>