At low heat levels, the fans operate at low speeds. As the temperature of the PA rises, the fans increase in speed (and they're louder). Depending on humidity, ambient temperature, and the free space around the amplifier, the increased fan speed moves heat energy out of the amplifier.
If the PA transistors get "too warm", the firmware causes a temperature-related fault. That shuts the amplifier down until the temperature returns to a safe level. During development a number of amplifiers were subjected to very long key down times, sometimes with restricted airflow. We've exercised the protection logic quite a bit. That doesn't mean you need to run with all the knobs to the right, but if the fans are running, that's good, heat is being moved out. The PA devices are not being operated at their maximum thermal rating. The KPA500 temperature fault occurs before the RF transistor manufacturer's maximum temperature rating. Dick, K6KR -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Phil LaMarche Sent: Saturday, July 30, 2011 11:49 AM To: [email protected] Subject: [Elecraft] Advice! When running the KPA500 on AM, it there any time limit before unkeying? While operating, the fan comes on and then it kicks into another speed. Thanks Phil Philip LaMarche LaMarche Enterprises, Inc <mailto:[email protected]> [email protected] <http://www.lamarcheenterprises.com/> www.LaMarcheEnterprises.com 727-944-3226 727-937-8834 Fax 727-510-5038 Cell <http://www.w9dvm.com/> www.w9dvm.com K3 # 1605 KPA500 # 029 CCA 98-00827 CRA 1701 W9DVM ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
