[Elecraft] K3 Current Drain When Off

[Geoffrey Downs]

Re Wayne's possible explanation:  My K3 (#266) draws around 39ma when it's 
off and the 13.8v psu is on. It seems to be working normally in all 
respects. Of course when my K3 is turned off the psu still delivers 13.8v 
unless it, too, is turned off so if K3s do not turn off all the way when 
there is still voltage on the supply lines it's probably not surprising that 
current is still drawn. However, apparently some K3s draw 5ma or less when 
off and at least two (Jim K9YC's) a lot more than mine. I am puzzled. Am I 
misunderstanding something?

73 to all

Geoff
G3UCK

On October 16 Wayne wrote:

"Here's one possible explanation:

The external power supply must drop all the way to zero V, as must any all 
K3 I/O signals. This may have implications for attached equipment.

If there's any residual voltage on the supply or I/O lines, even 1 V, the K3 
may not turn off all the way. It turns out that the brown-out detection 
circuitry on microcontrollers can be confused at some power levels that are 
low enough to look like a brownout but not high enough to properly power the 
detection circuitry. Under such conditions the MCU may continue to run on 
power-down via the on/off switch, resulting in the radio drawing an 
unpredictable amount of current."