[Elecraft] K2 no transmit, and no sidetone

[bills4570@att.net]

Hi all, 

I'm working on K2 serial 2862 for a friend.  He recently replaced P4 on the 
control board, and cleaned up some errors in wiring the mic configuration.  
Up to that time the K2 was working fine; being used solely on PSK-31.  The 
unit is the QRP version with SSB board, battery and no other options.

When I received # 2862 there was no transmit on CW or SSB, and there was no 
sidetone/spot tone.  There's no spot tone at the output of contol board U6, 
and I suspect this has someting to do with no RF output.

The unit draws 2.5 amps (possibly more) key down, but does not produce RF 
output. All resistance checks are good for the RF amp section and the driver.

The receiver is working fine on 40M, and the alignment and signal tracing on 
the receive path looks OK.

Not knowing the logic of the control board U6 and other chip components, I 
can't tell what their function is supposed to be, so can't trace any logic 
through them.

Any ideas on what might be wrong, and what to check?

--
Bill Schwantes
W7QQ  K2 2715