Low power out, ERR TXG when trying to calibrate power

[M0VFC]

Hi folks,

My KX3 seems to have developed a low output power problem.

All used to be fine, but over the weekend I noticed it now only gives ~6W maximum on CW despite a good SWR indication. I have reproduced this into a dummy load (1.1:1 SWR) and checked DC input voltage (11.2V key down, external 3S LiPo).

Additionally, if I engage the ATU, it no longer seems able to find a good match, even into a dummy load. Bypassing the ATU results in an indicated 1.1:1 SWR, and removing the ATU module does not fix the low output power problem.

If I run the manual TX power calibration (set power to 6W and hold TUNE), the VFO B display reaches about 5.4W then stays there. Tapping TX to stop the procedure results in ERR TXG being shown. Doing the same at 4W results in maximum output power of about 3.2W, from memory, and a similar ERR TXG error.

This is true on all HF bands.

Any thoughts on where to look?

Many thanks,
Rob, M0VFC

[Don Wilhelm]

Rob,

I would try running the TX Gain Calibration with a higher voltage power
source - at least 13.8 volts.

If it still fails, contact Elecraft support.

73,
Don W3FPR

On 4/18/2017 5:55 AM, M0VFC wrote:

> Hi folks,
>
> My KX3 seems to have developed a low output power problem.
>
> All used to be fine, but over the weekend I noticed it now only gives ~6W
> maximum on CW despite a good SWR indication. I have reproduced this into a
> dummy load (1.1:1 SWR) and checked DC input voltage (11.2V key down,
> external 3S LiPo).
>
> Additionally, if I engage the ATU, it no longer seems able to find a good
> match, even into a dummy load. Bypassing the ATU results in an indicated
> 1.1:1 SWR, and removing the ATU module does not fix the low output power
> problem.
>
> If I run the manual TX power calibration (set power to 6W and hold TUNE),
> the VFO B display reaches about 5.4W then stays there. Tapping TX to stop
> the procedure results in ERR TXG being shown. Doing the same at 4W results
> in maximum output power of about 3.2W, from memory, and a similar ERR TXG
> error.
>
> This is true on all HF bands.
>

... [show rest of quote]

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[M0VFC]

Just to update on this thread: repeating the calibration on 10MHz with 13.8V applied does get to 4/6W indicated on the VFO B display, but on tapping XMIT, still gives ERR TXG (D=228 or thereabouts on the main bit of the display). I'll drop Elecraft an email.

73,

Rob, M0VFC

On 18 April 2017 at 13:07, Don Wilhelm [via Elecraft] <[hidden email]> wrote:

Rob,

I would try running the TX Gain Calibration with a higher voltage power
source - at least 13.8 volts.

If it still fails, contact Elecraft support.

73,
Don W3FPR