[Elecraft] [K3] Strange Selective Hearing in My K3

[Michael Carter]

Hi Eric,

I'm voting with my friend Dave, K1WHS,
for looking first at the voltage regulators.

The 8 volt regulator supplies the TC4427
gate driver IC, which in turn provides 7R/7T voltages
separately to the Transmit and Receive switching circuits.
The loss of the 7R/7T voltages would disable the
PIN diode T/R switches and render the radio deaf
and unable to transmit.

If the 8 volt regulator doesn't collapse after some
time observing its output voltage, I would check
the TC4427 (U11 on the RF Board) to be sure its
outputs are correct (the 7R/7T voltages).  The
regulator is likely the first culprit - its '8A' output
pin provides power to a large number of circuits
in the radio.

73,
Mike, K8CN