K3S - No high power output - Low power OK

[Ken Bolin]

My K3S is about 3 years old and is S/N 11185. It has operated flawlessly
since it got out of the box.

 

I was using it this weekend in the VHF contest and operated perfectly until
Sunday afternoon. I took a break for dinner and came back about two hours
later and found that I had no power output. The radio was left on during
that time. There was no indication that there was a power surge of any kind
and there was no smell of anything electrical. Since I wasn't transmitting
during that time, there was no SWR issue.

 

After doing some initial troubleshooting, I found that the rig worked
perfectly at low power but when I go above 9 watts (12 watts on HF) I get no
output. The display indicates two dashes where the SWR is displayed and the
power indicates 0.0 W.  When I try to transmit with higher power, the red TX
light comes on steady and the K3S also keys my amplifier properly. I've
tried it on several bands with the same results.

 

The only other thing of interest is that when I came back to the rig after
dinner, the rig tried to transmit in CW while receiving in TX Data. I did
not leave it in that configuration. That may indicate that something my have
happened with the S/W settings.

 

Any suggestions of where to start looking

 

Thanks

Ken W1NG

[hidden email]

 

 

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[Ben Gelb-2]

Hi Ken -

I had a similar issue with my K3S in May (SN 11272 - very similar age).

I detailed it in this thread:
http://mailman.qth.net/pipermail/elecraft/2020-May/275684.html

It ended up that R5 on the KPA3A board (part of QSK T/R switching
circuit) had a broken solder connection due to the fact that the
component does not match the footprint mechanically on the PCB, and so
a solid connection is basically impossible (Elecraft confirmed this
was a problem with Rev D of the KPA3A, which I have, and that it was
corrected in Rev E). I was able to fix it by moving the component
slightly to borrow some PCB copper from an adjacent component.

In my case I found that the problem affected transmit (as you
describe) but also receive. If I dialed the power knob up and down
across the low/high power threshold while listening on a busy band,
I'd hear all the noise go quiet when I moved to high power and the PA
switched in. It was also intermittent, at least initially - I guess
thermal heating/cooling made the bad connection go in and out. So this
may be a good debugging step to try to determine if it is the same
problem.

Good luck debugging your issue. I will be interested to learn if it is
the same problem.

73,
Ben

On Mon, Jun 15, 2020 at 8:30 AM Ken Bolin <[hidden email]> wrote:

>
> My K3S is about 3 years old and is S/N 11185. It has operated flawlessly
> since it got out of the box.
>
>
>
> I was using it this weekend in the VHF contest and operated perfectly until
> Sunday afternoon. I took a break for dinner and came back about two hours
> later and found that I had no power output. The radio was left on during
> that time. There was no indication that there was a power surge of any kind
> and there was no smell of anything electrical. Since I wasn't transmitting
> during that time, there was no SWR issue.
>
>
>
> After doing some initial troubleshooting, I found that the rig worked
> perfectly at low power but when I go above 9 watts (12 watts on HF) I get no
> output. The display indicates two dashes where the SWR is displayed and the
> power indicates 0.0 W.  When I try to transmit with higher power, the red TX
> light comes on steady and the K3S also keys my amplifier properly. I've
> tried it on several bands with the same results.
>
>
>
> The only other thing of interest is that when I came back to the rig after
> dinner, the rig tried to transmit in CW while receiving in TX Data. I did
> not leave it in that configuration. That may indicate that something my have
> happened with the S/W settings.
>
>
>
> Any suggestions of where to start looking
>
>
>
> Thanks
>
> Ken W1NG
>
> [hidden email]
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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