[Elecraft] [K2] :Transmitter allignement (40M): Power control failure ....

[Don Wilhelm]

Jean,

The K2 measures the RF output and sends the resulting DC voltage to the 
MCU.  If no power is detected, the K2 will increase drive in an attempt 
to bring the power up to that requested by the power knob. In fact, the 
power will go to maximum and produce Hi Cur messages.

You probably have a problem with the RF Output detector.  See the 
schematic for the RF Board sheet 3 near the lower right corner.
Check diode D9 for orientation (check against the parts placement 
diagram at the back of the manual).
Make certain you have not interchanged R68 and R68 and have not 
interchanged R66 and R69 - check those resistor values - check the 
soldering of those components.

On the Control Board, check the resistance between P4 pin 10 and U6 pin 
2.  Resistor R12 is between those two points and you should read 820 ohms.

If no problem is found there, set the K2 at 2 watts and measure the DC 
voltage on the VRFDET signal line - it can be found on the Control Board 
P4 pin 10 and at U6 pin 2.

I hope you find it.

73,
Don W3FPR

On 7/12/2013 12:25 PM, Behiels JeanPierre wrote:
> Hi K2 builders;
>
> I just have finished with the build of my K2 CW/SSB base 10W vesion.
> Before I will continue with the build-in my KPA100 unit I will do a whole K2 transmitter final allignement.
> I already have done a receiver allignement so the band coils should be quit in the naber for maximum power output..
> I do have set my CAL CUR to 3.5A (like manuals told)
> I start with the allignement of the 40M band coils (see K2 manual page 78).
> A dummy of 50 ohm/1Kw with in series a power meter (Daiwa CN620A) is connected at the anteen output(BNC connector of K2).
> I do have set my power control to 2.0 W like manual tolds.
> I put the K2 in TUNE mode and read easely about 20W on  my power meter installed between K2 and 50 ohm dummy load.
> I do always receive a high current warning message (with is normal with a power output of 20W current reading is about 4A an dmore !!!!)
> But I can do any POWER control adjustement while turning on the power control potmeter on the frontpanel.
> When I am in the receive mode and turning on this power control I can change de LCD reading from P 0.1W to P 15.2 W
> So I presume the software is working well ?
> With the power control set to P 5W I obtain a current on LCD display of about 4.5A (and a HI Cur message)
> The voltage reading on the K2 LCD fluctuate from 7.0 VDC to 9.0 VDC
> But this indication is not a power supply failure because I measure the output voltage on the connector of the power supply with a Fluke DMM and this voltage stays stady around +13VDC !!!!!!!!!!!!!!!!!!!
> So power more than enough but no control so far ... ?
> Did should I ear a CW keying tone when I am in TUNE mode,I do ear nothing while I am tuning ...
> I am in CW normal mode with no PRE activated...
> Voltage and curren readings in RX are next values : E12.7 i0.24
> Any suggestions what could be the reason.
> I do have same sympthome on other bands also,always 20W and no power control ?
>
> Regards Jean ON4AEF
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