[Elecraft] Upper limits of KPA500?

[Dave Cole]

Pure paranoia!  :)

I tend to creep into things I consider limits, and not race to them.  I 
normally run the amp in such a way that it never exceeds 60 or at worst 
65 C.  Seeing it hit 70 makes me nervous...

So...

Prior to any excursions in to the above 70C area I need to learn more, 
which is what your post just helped me do!  Thank you!!

Knowing that others can run the KPA500 90C, eases my fear of amp final 
damage.

I have always ran tube amps in the past, and at one point owned a very 
sensitive SS amp, which killed a few sets of finals.

It turns out there were other issues at play, (design issues I think), 
but that experience made me very jumpy about SS amps.  I almost went 
back to tube amps prior to purchasing the KPA500.  After owning KPA500 
for a while now, I would never go back to tubes...  So I am being as 
careful as possible to insure I understand what I am asking the amp to 
do, before I ask it to do something it was not designed for.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 5/3/20 1:36 PM, Jack Brindle wrote:
> Dave;
> 
> The KPA500 will protect itself above 90C, but it will work quite well at 70C. Why do you stop at 70C?
> 
> 73!
> Jack, W6FB
> 
> 
>> On May 3, 2020, at 1:26 PM, Dave Cole <dave at nk7z.net> wrote:
>>
>> Hello,
>>
>> I just got the new MMSSTV software, and will be running a bit of SSTV. SSTV is 100% duty cycle.
>>
>> Initial testing here indicates no power level is safe...  At 150 watts the KPA500 reaches 70C pretty fast, in under two minutes, and 70C is my upper limit for testing...  At 500 watts it reaches 70C in about the same time...
>>
>> Can I assume the amp is not the most efficient thing in the world at 200 watts?
>>
>> If the KPA500 can't deal with 100% duty cycle, for two minutes, how does the K3 deal with 100 watts for two minutes, at 100% duty cycle?
>>
>> -- 
>> 73, and thanks,
>> Dave (NK7Z)
>> https://www.nk7z.net
>> ARRL Volunteer Examiner
>> ARRL Technical Specialist
>> ARRL Asst. Director, NW Division, Technical Resources
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to jackbrindle at me.com
>