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K2 Transmitter problem, Alignment and Test Part III

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N8CEP

K2 Transmitter problem, Alignment and Test Part III

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.

Please forgive my probably poor explanation.

Keith Hamilton W8GX
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Don Wilhelm-3

RE: K2 Transmitter problem, Alignment and Test Part III

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.
>
>

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Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
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Elecraft web page: http://www.elecraft.com

N8CEP

Re: K2 Transmitter problem, Alignment and Test Part III

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.
>>
>>
>
>
>