Richard,
The K2 (and K3 and KX3) control power using a closed loop system. That
means there must be some means of measuring the actual power output
right at the antenna - that measurement is compared with the power
requested by the power knob in the MCU, and the drive is adjusted as
required to make the actual power output match that requested.
Now consider what would happen if the wattmeter at the output of the
KPA100 were not functioning properly - there would be low or zero power
reported to the MCU and the MCU in turn would try to increase the power
to bring it up. Of course, even at maximum power, the MCU would still
think there is no power being produced.
Bottom line - there is something wrong with the wattmeter in the KPA100.
The first suspects are diodes D16 and D17.
Secondary suspects are U5 (not likely, but possible) and U6. U6 does
sometimes fail for reasons unknown, but do check D16 and D17 carefully
(or simply replace them) because that is the most common cause of
wattmeter failure.
73,
Don W3FPR
On 5/18/2014 7:40 AM, Richard wrote:
> A fellow ham is having the following problem withhis K2:
>
> A year ago, we installed the KPA100 which worked fine until recently.
>
> Suddenly, the TX Power Control failed and the K2 will deliver either
> 9-15 W or - with the 100W PA switched on - up to 150 W into a dummy load.
>
> I suspect there is an issue with the TX-ALC, but no defective diode
> was found.
>
> I personally don't own a K2 but is there a TX gain calibration
> procedure similar to the K3?
>
> Suggestions welcome - thanks in advance.
>
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