[Elecraft] K2/100 KPA100: Cannot Adjust tPA, Stuck at 0C

[Ian Greenshields]

 Hi Don, all,

 Thanks for the help & suggestions. Pin 5 of U1 is 0.6v but CAL tPA cannot be
 adjusted. Looks like the MCU on the KPA100 is faulty. I've ordered a new
 one.

73 Ian G4FSU

On 10/04/2008, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> Ian,
>
>  Put the K2 into CW test mode (in CW, press and hold the MODE button), set the power level to something above 11 watts - press TUNE and measure the voltage at KPA100 U1 pin 5.  The voltage will normally be close to 0.6 volts.
>
>  If the above measurement is correct and you still cannot adjust CAL TPA, then I suggest that you replace the KPA100 MCU.
>
>  OTOH, If the measured voltage is substantially different than 0.6 volts, check the KPA100 bias as instructed in the manual - if that is found to be grossly incorrect, check R5, R6 and Q3 (refer to the schematic) to be certain these components are receiving the proper voltages during transmit (use CW TEST mode).
>
>  73,
>  Don W3FPR
>
>
>  Ian Greenshields wrote:
>
> >  After repeating the power calibration on my K2 KPA100 due to low
> >  output power, I found the CAL tPA function had reset to 0C and can no
> >  longer be adjusted.
> >
> >  Having pressed EDIT from the CAL tPA display, the display shows tPA
> >  0C, but turning the VFO knob has no effect on the display, it remains
> >  resolutely at 0C.
> >
> >  Scanning the archives dug up a couple of similar issues, but no
> >  solution. Has anyone seen this? Is the there a fix? Is my brain
> >  disconnected & I'm doing something stupid (most likely scenario, I'll
> >  admit)?
> >
> >  I'm now concerned that having fixed the output power, the fan won't
> >  switch on when it's needed.
> >
> >
> >
>