I can answer this. It is normal. The microcontroller is on, but sleeping when the rear-panel power switch is on. It needs to run to be able to respond to serial commands and for the front-panel power-on button to work. It is powered by the 5V linear regulator, which is providing the heat you feel, along with the +12V and -12V regulators (also linear). I seem to recall that the input to the regulator is something like +15 or +18V, which gets regulated down to the three supplies that are used for running the microcontroller the RS-232 interfaces and the LCD. The LCD is disabled when front-power is off.
So yes, the small amount of heat you feel is quite normal. 73, Jack, W6FB > On Jun 30, 2021, at 3:16 PM, Dave <[email protected]> wrote: > > I would assume so, as mine is the same way... So unless both of our KPA500's > have failed in the same way, at the same time, it is more than likely normal. > A short call to Elecraft will answer your question with more surety. > > 73, and thanks, > Dave (NK7Z) > https://www.nk7z.net <https://www.nk7z.net/> > ARRL Volunteer Examiner > ARRL Technical Specialist, RFI > ARRL Asst. Director, NW Division, Technical Resources > > On 6/30/21 12:35 PM, Andy Durbin wrote: >> "But, is this normal? I assume that there is a small current powering a >> micro processor and its related circuitry but should it be actually that >> warm — is there a cpu burning "idle loop" used and thus causing high current >> flow thru the processor." >> My KPA500 draws 0.14 A when "On" and in standby mode. It draws 0.10 A when >> "Off" with rear power switch still on. Both measurements at 117.2 VAC (A/C >> is running at my house and probably every other house on the same >> transformer). >> Yes the CPU is active when "Off". It has to be for the KPA500 to be turned >> on my serial command. >> "The KPA500 uses single character commands when in boot mode. Boot mode is >> the state the KPA500 is >> in when the rear panel power switch is in the ON position, while the main >> firmware is not running. This >> mode is used for starting up the KPA500 or downloading fresh firmware. >> Bootloader commands must be >> sent upper-case only." >> 73, >> Andy, k3wyc >> ______________________________________________________________ >> 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 >> Message delivered to [email protected] <mailto:[email protected]> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > <http://mailman.qth.net/mailman/listinfo/elecraft> > Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm> > Post: mailto:[email protected] <mailto:[email protected]> > > This list hosted by: http://www.qsl.net <http://www.qsl.net/> > Please help support this email list: http://www.qsl.net/donate.html > <http://www.qsl.net/donate.html> > Message delivered to [email protected] <mailto:[email protected]> ______________________________________________________________ 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 Message delivered to [email protected]
