[Elecraft] K2 Problem: Audio Stuck in "Mute"

[JimWMiller@aol.com]

Hello,

Here's an interesting problem that I hope others have solved.

I've just completed the initial building of the RF board and was testing the 
40 meter receive capabilities.  The transmit section is not yet build.  The 
problem is that the audio is muted. The audio gain control has no effect 
although I can heard sidetone OK. No hiss can be heard. All control functions 
and the display are fine.  

Electrically the K2 is in mute as seen by the following voltages:

On Control board:
U6, pin 17, mute =  5volts   //always muting !!!!
U6, pin 27, TX = 0 volts      //Not transmitting
U6, pin 28, RX = 5 volts      //always receive
8T = 0 volts                         //seems ok
8R = 8 volts                         //seems ok

For some reason the microprocessor keeps the mute line high. Perhaps the K2 
thinks it is transmitting however the TX line is low !!!

Anyone have any clues as to why the mute line is always high ???
Has anyone had this problem?

Thanks in advance.

Stuck in "Mute",
Jim WA2UMP
K2: 2679


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