[Elecraft] Temperature or Warmth of KPA500 when "Off" ?

[Jack Brindle]

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 <dave at nk7z.net> 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
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> 
> 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
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