[Elecraft] K2 no transmit power

[James T. "Jim" Rogers]

Rich,
Look at the two transistor switches(Q1 and Q2) on the control board
schematic just below the MCU. The output of one  switch will be 8R. This
powers the receiver on receive. The output of the other is 8T. This powers
up the transmitter on transmit. As you switch from transmit to receive and
vice versa, you should see these two lines switch.

I have been racking my brain to offer a solution to you regarding the
sidetone issue you mentioned. There were a couple of messages on the
reflector about selecting the sidetone source in the K2. Your kit and mine
are very close in serial number. I know the default is U8 pin 1, the DAC
just to the right of the MCU on the control board schematic. Sidetone
generation here is independent of band.

To me it seems that in having problems with sidetone and power, you have two
or more issues that normally would not be related.

Take one problem at a time and try to resolve one. Check TX on the MCU. Does
it go high on transmit? IF it does check the line 8T from the transistor
switch I mentioned earlier. You should see 8V when in transmit. It should go
to 0 on receive. If TX is held low, look for something pulling it down like
a solder bridge etc.

I know it is a long wait until Monday, when Gary will be back in the office
at support@elecraft.com but when all else fails he is a whiz. He has seen
most problems you would ever run across and he is most generous with his
informational resources.

I have been monitoring your messages all afternoon and could not bear to let
you go on without any answer or encouragement. Good Luck, the K2 is a great
little rig. I had several problems myself with my kit and even managed to
short a line to 12v and shot the /MUTE line out of the MCU and had to
purchase another one.

73 Jim W4ATK
K2 #4028