[Elecraft] K2 - Clean +5V for mic pre-amp

[Stewart Baker]

I gave up using the 5A rail that supplies the Microphone jumper and Microphone 
socket for a preamp either internal or external - too much electrical noise, and 
adverse effects on MCU operation etc.

Via Pin7 of P1 on the Front panel board I  connected the 8A rail to the input of 
a small 3 terminal 5V regulator (78L05) which is mounted on the Front panel 
board. The regulator output has a 47uF and a 0.1uF capacitor to decouple it.
I disconnected the 5A supply  feed  to the Microphone jumper, and connected it 
to the new +5V supply.

End result I can draw what current I need (within reason), there is NO noise, 
and no possibility of upsetting the K2 firmware with loading or RF feedback.

73
Stewart G3RXQ