[Elecraft] K2 no transmit power

[Don Wilhelm]

Rich,

At this point, I can't tell you specifically is the problem, but if Q24 has
drain voltage when in CAL FCTR state, then the microprocessor feed to the
DAC (control board U8) should be functioning properly and control baord U10A
and Q8 should also be working properly.

I would recommend that you look at the path for VRFDET from its source at RF
board D9, R66, etc, and through the connectors to the control board, through
Control board R12 then on to the microprocessor pin 2.

The microprocessor actually controls VALC.  I am guessing, but if the
microprocessor pin 2 is at a relatively high voltage level for some reason
(my guess is this is what is not working), the uP senses that there is
already too much power and will attempt to reduce the value of VALC.  Check
for uP pin 2 for proper plugging in its socket too, an electrically floating
pin could be the cause of your problem.

Let me know how my theory checks out.

73,
Don W3FPR

----- Original Message ----- 

After checking once again for shorts, wrong parts, etc I still haven't come
up with an answer why I can't get TX power on any band.  I have looked and
found the following:
1.   EXCEPT  when using the internal frequency counter set up from the CAL
menu, there is NO voltage on the drain of Q24 which supplies RF injection to
the XMIT mixer.  Is this normal.?   I am checking this with the key in CW
mode,  key down or key up.

...snip
6. When I am in OPER mode (not test) and I attempt to key the K2, I get a
periodic burst of carrier for a few milliseconds.  It looks like power
turndown is shutting off the rig at the trailing edge of the short burst.
Checking V-ALC from the emitter of Q8 on the control board shows no voltage
at all except when in the condition in item 1.  I thought incorrectly that
this is supposed to be turndown for too much TX power coming from V PWR.