[Elecraft] KLPA3A power transistor thermal stress concerns

[Nr4c]

Yes. But I believe that is Junction temperature, not case on heatsink temp.  Remember the case bottom is heatsink for those. Make sure screws are tight. 

Sent from my iPhone
...nr4c. bill


> On Oct 27, 2017, at 12:19 PM, N2TK, Tony <tony.kaz at verizon.net> wrote:
> 
> 50C is not hot for a transistor. Commercial transistors are usually speced to 85C. JANS (space) transistors are speced to 125C and actually baked without bias for 320 hours at 200C. The hFE is measured before and after to check for change.
> 73
> N2TK, Tony
> 
> Sent from my iPad
> 
>> On Oct 24, 2017, at 8:23 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>> 
>> Nick,
>> 
>> Yes, I believe that should be no problem.
>> 
>> 73,
>> Don W3FPR
>> 
>>> On 10/24/2017 8:57 PM, Nick - VE3EY wrote:
>>> 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,
>>> 
>> 
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