[Elecraft] K2 Transmitter problem, Alignment and Test Part III

[Keith Hamilton]

The voltage measured at P4 10 is 0 going to 1.2 when transmitting. The
voltage measured directly on U6 pin 2 is 0 going to about 6.2 volts when
transmitting. I resoldered R12 and double checked U6 pin 2.

I'm really puzzled now.
Thanks for the help!

Keith Hamilton




Don Wilhelm wrote:
> Kieth,
> 
> FB on your K2 symptoms - yes that was a good description.
> 
> OK, for the explaination:  The K2 detects the power output and sends it to
> the microprocessor on the VRFDET signal line.  If the VRFDET line indicates
> a power level less than the power requested by the power control knob, the
> uP will take steps to increase the power output in an attempt to get it as
> high as the power requested.  Since your K2 is developing full power output
> regardless of the power control setting, the most likely cause is with the
> VRFDET signal.
> 
> Start at the RF voltage detector D9 - be certain it is oriented properly
> (the parts placement diagrams are handy for that check), and that everything
> in that area is properly soldered - check the schematic for the related
> components.  The VRFDET signal makes its way back to the uP (Control Board
> U6 pin 2) where the firmware takes over its task.  You can easily check to
> see if there is any voltage on Control Board P4 pin 10 during transmit - if
> not, the problem likely is with the detector circuit, but if there is a good
> voltage at CB P4 pin 10, then the problem lies on the control board - in
> this case, check R12 and U6 pin 2 for proper soldering.
> 
> Poor solder connections are the most common cause of problems with the K2,
> so check the soldering, and then re-check the soldering - when all that is
> complete, check the soldering!
> 
> Once the microprocessor is signaled that there is power present, the
> situation will settle down to something more normal.
> 
> 73,
> Don W3FPR
> 
>> -----Original Message-----
>>
>>
>> I am having a problem with my transmitter testing. When I try to
>> transmit my K2 says "Hi-Cur" and the power indication stays at 0.1.
>> However the wattmeter I have attached to the antenna indicates 10 watts
>> or more. I have the wattmeter hooked up to a dummy load. I tried
>> connecting it to my antenna with the same results. I can't align the 40
>> meter band-pass filter inductors because the transmitter is putting out
>> too much power. It seems like the transmitter is going full bore and
>> nothing in the radio is telling it to slow down. And I don't understand
>> the 0.1 power indication on the K2 meter.
>>
>>
> 
> 
>