[Elecraft] KPA/100 displays wrong PS current (much lower)

[Don Wilhelm]

Ioannis,

Back the CAL CUR down to 3.50.
It may be that you will have Hi Cur messages if you turn the POWER knob 
to full clockwise, but if you set the power control at 100 watts, that 
message should not appear.

If it does, check the connections from the power supply to the 
K2/KPA100.  If the voltage at the K2 (observe with the K2 voltage 
display) drops significantly during keydown, that could explain the Hi 
Cur warnings. Tighten the power supply terminals and check to be certain 
the APP connector is properly assembled with the connector blades fully 
inserted.  If you look at the end of the APP connector and can see the 
spring blades that normally lock the contact blade, the contact blade 
has not been fully inserted and will not make full contact (and cause a 
significant voltage drop).
If you can increase your power supply voltage to 14.3 volts or above, 
you should increase the voltage.  The K2 will operate with voltages up 
to 15 volts.  For linearity and best transmit IMD, the higher the 
voltage, the better.

73,
Don W3FPR

On 4/24/2016 4:07 PM, Ioannis Kassotakis wrote:
> Thanks Don,
> I understand that the PS current reading is only for the Base K2.
> I will rely on the bench PS display to read the 13.8 DC current.
> I have already set the CAL CUR to 3.8 Amps so that I do not get HI CUR 
> alert at 10 Watts.
>
> 73,
> Ioannis PA1EQP
>
>
> On Sunday, 24 April 2016, Don Wilhelm <donwilh at embarqmail.com 
> <mailto:donwilh at embarqmail.com>> wrote:
>
>     The current display on the K2 is only for the current used by the
>     base K2.  I use it when testing the K2 for 'good health' and
>     normal RF Gain, but during operating I see no need to monitor it
>     on a regular basis.
>     The Base K2 will indicate Hi Cur if the current draw goes above
>     the value set by the CAL CUR parameter, and will reduce power if
>     that occurs.  Should you continue to get Hi Cur messages, that is
>     an indication of something that should be investigated.
>
>     73,
>     Don W3FPR
>
>     On 4/24/2016 3:14 PM, Ioannis Kassotakis wrote:
>
>         Thanks Don,
>         That means that at HI PWR (>11 Watts) should disregard the
>         displayed PS current figures.
>         I thought that KPA100 processor would communicate the I Sense
>         back to the MCU and display the correct current figure after
>         rescaling. I understand that is not the case.
>
>         73,
>
>         Ioannis PA1EQP
>
>         On Sunday, 24 April 2016, Don Wilhelm <donwilh at embarqmail.com
>         <mailto:donwilh at embarqmail.com>> wrote:
>
>             Ioannis,
>
>             The current display on the K2 indicates only the current
>         for the
>             base K2, not for the K2 and KPA100 combination.
>             That is why you set the CAL CUR to 3.50 amps even though the
>             KPA100 will draw much more current.
>
>             Yes, the KPA100 does have a scaling on the amount of RF
>         voltage
>             that is being detected.  That is used for power control
>         and has
>             nothing to do with the current displayed.  The result of that
>             voltage is sent to the VRFDET signal in the K2 (Voltage of
>         the RF
>             Detected).
>
>             73,
>             Don W3FPR
>
>
>
>
> -- 
> Ioannis Kassotakis