RE: K2 power control

Posted by Don Wilhelm-3 on Jun 04, 2006; 1:49pm
URL: http://elecraft.85.s1.nabble.com/K2-power-control-tp390511p390514.html

Jeorg,

There is one more place to check before replacing U6 - check to see if U6
pin 8 goes to almost 5 volts during transmit (this is the chip enable
signal) and check that pin 7 has the 5 volt supply on it.

If pin 8 does have the 5 volts, then the firmware is properly enabling the
chip, but if the voltage is not present, the problem goes back to the KPA100
firmware chip.

If pin 7 does not have 5 volts on pin 7, then that must be fixed first -
check the regulator at U3.  This latter possibility is not as likely since
the firmware chip uses this voltage too, and if you can turn the PA on and
off in the K2 menu, the firmware in the KPA100 is probably working.

73,
Don W3FPR


> -----Original Message-----

>
> Don,
>
> I checked the voltages during quick keydown.
>
> U5 pin 5     2,5 V
> U5 pin 7     2,5 V
> U6 pin 3     2,5 V
> U6 pin 6     0,06 V
>
> It looks like U6 is killed. Pin 6 does not show 2,5 V during transmit. I
> think I know what was happend ;-)
>
> I soldered a new cable for my KAT100 tuner to extent the length. I
> forgot to disconnect the AUX connector from K2 side. Pin 6 of U6 is
> connected to pin  7 of the AUX I/O port.
>
> I will replace U6 and test again.
>
>
> 73 de Joerg (DL3QQ)
>
> -----Original Message-----
> Date: Sun,  4 Jun 2006 04:30:01 +0200
> Subject: RE: [Elecraft] K2 power control
> From: "Don Wilhelm"
> To: , "Elecraft"
>
> Joerg,
>
> You either have something wrong with the wattmeter in the KPA100 or have
> something wrong in the path from the wattmeter forward power circuit to
> the
> VRFDET output from the KPA100.
>
> During a quick keydown period (with only the base K2 powered or with the
> PA
> turned off in the menu), check the following points on the KPA100 (in
> order)to determine at which point the voltage disappears - these should
> all
> be DC voltages - you should expect about 4 volts when the base K2 is
> developing 10 watts or more:
>
> U5 pin 5
> U5 pin 7
> U6 pin 3
> U6 pin 6
>
> U6 pin 6 is the KKPA100 output signal for the VRFDET line, and if you
> have
> voltage to that point, look for an open in the ribbon cable (pin 10).
>
> 73,
> Don W3FPR
>
>
> > -----Original Message-----
> >
> >    I  need  some  help.  I  can  not  adjust  my power anymore when K2
> is
> >    connected   to   the  100  W  PA.  The  PA  is  overloaded  and
>  power
> >    meter shows 200 watt !!!
> >
> >    I tried  to switch off  PA in menu, but in this ca=e it is still
> >    running with maximum QRP power.
> >
> >    I assume something goes wrong with VRFDET.
> >
> >    If I disconnect th= PA from K2 power adjustment works fine.
> >
> >    How could I investigate to find the reason for this fault ?
> >
> >    73 de Joerg (DL3QQ)
> >
>
>
>
>
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